influence of packaging materials and storage...

INFLUENCE OF PACKAGING MATERIALS AND STORAGE CONDITIONS ON THE QUALITY ATTRIBUTES OF

POTATO (Solanum tuberosum L.) TUBERS

KASHIF SARFRAZ ABBASI

95-arid-33

Department of Food Technology

Faculty of Crop and Food Sciences

Pir Mehr Ali Shah

Arid Agriculture University, Rawalpindi

Pakistan

2012

INFLUENCE OF PACKAGING MATERIALS AND STORAGE CONDITIONS ON THE QUALITY ATTRIBUTES OF

POTATO (Solanum tuberosum L.) TUBERS

by

KASHIF SARFRAZ ABBASI (95-arid-33)

A thesis submitted in partial fulfillment of the requirement for the degree of

Ph.D Agriculture

in

Food Technology

Department of Food Technology

Faculty of Crop and Food Sciences

Pir Mehr Ali Shah

Arid Agriculture University, Rawalpindi

Pakistan

2012

ii

CERTIFICATION

I hereby undertake that this research is an original one and no part of this thesis falls

under plagiarism. If found otherwise at any stage, I will be responsible for the consequences.

Student’s Name: Kashif Sarfraz Abbasi Signature. ____________

Registration No: 95-arid-33 Date.

Certified that the contents and form of the thesis entitled “Influence of Packaging

Materials and Storage Conditions on the Quality Attributes of Potato (Solanum

Tuberosum L.) Tubers” submitted by Mr. Kashif Sarfraz Abbasi have been found

satisfactory for the requirement of the degree.

Supervisor ________________________ (Prof. Dr. Tariq Masud)

Member ___________________________ (Dr. Asif Ahmad)

Member __________________________ (Prof. Dr. Muhammad Gulfraz) Chairman _____________________

Dean _____________________ Director Advanced Studies ______________

iii

IN THE NAME OF ALLAH

THE MOST MERCIFUL THE MOST

BENEFICIANT

iv

DEDICATED

TO

THE LOVING MEMORIES

OF

MY DECEASED FATHER

v

ACKNOWLEDGEMENT

I am highly indebted to Almighty Allah (The compassionate the most merciful) who

blessed me enough to carry out this humble effort in the form of present dissertation. I offer

my humblest compliments from the core of my heart to our beloved Prophet Muhammad

(Peace Be Upon Him) the city of knowledge, the highest of mankind who enlightened and

turned the lives of mankind into peace and great moral values.

Triumph begins with the role of parents to culture principles while completes with

the guidance of a teacher. I feel privileged to be associated with my affectionate supervisor

Prof. Dr. Tariq Masud, Chairman, Department of Food Technology who guided me during

the course of this research work with words of wisdom and progressive vision. I am

extremely grateful for his inspiring guidance, generous assistance, and constructive criticism

for the accomplishment of this manuscript.

I am thankful to the worthy members of my supervisory committee; Prof. Dr.

Muhammad Gulfraz and Dr. Asif Ahmad for their scholastic guidance and kind co operation

through out the period of my PhD studies. Sincere thanks are extended to Prof. Dr. M.

Shahbaz Bhatti Ex. Chairman Deptt. of Food Technology for his in time guidance and

technical support. I must pay homage to all the other faculty members of Department of

Food Technology for their continuous support and valuable suggestions during my course of

study.

Its matter of great privilege for me to offer my sincere regards to Prof. Dr.

Muhammad Munir (Ex Vice Chancellor, Arid Agriculture University), Prof. Dr. Tariq

Mahmood (Chairman, Deptt. of Environmental Sciences), Prof. Dr. Muhammad Aslam (Ex.

Chairman, Deptt of Entomology), Dr. Khalid Saifullah Khan (Incharge Central Laboratory),

Mr. Muhammad Nisar (Controller Examinations), Mr. Sohail Mahmood Malik (Dy.

Controller Examinations, Federal Urdu University, Islamabad) Mr. Ayaz Elahi (Dy.

Registrar, Examinations) Dr. Riffat Hayat (Assistant Professor, Soil Science) and Mr.

Mahmood-ul-Hassan (Lecturer, Plant Breeding and Genetics) for their generous cooperation

and time to time assistance.

vi

I found myself fortunate enough to have the company of my Ph.D colleagues Dr.

Ahmad Bilal, Mr. Sartaj Ali, Mr. Talat Mahmood, M. Javed Tarin for their moral support

and judicious advice during my research work. I feel it appropriate to offer my deep sense of

appreciation to my friends Raja Rehan Arif (Marketing Specialist, F&VDP, Lahore), Mr.

Nazar Iqbal (Seed Analyst, FSCD, Islamabad), Dr. Farid Asif Shaheen (SSO, PSF,

Islamabad), Mr Abdus Sattar (NARC, Islamabad) for their valuable inputs during the write

up of this manuscript.

I express my thanks to Higher Education Commission of Pakistan for providing me

the financial assistance through Indigenous Fellowship program to make this project

possible.

Last but not least, I am very grateful to the endless prayer of my mother and all

family members for their patience, support and encouragement throughout my study.

Deepest gratitude I reserve for my wife, daughters and son for their patience and moral

support for my persuasion to higher ideals of life.

(KASHIF SARFRAZ ABBASI)

CONTENTS Page

vii

Certification ii

Dedication iv

Aknowledgement v

List of Tables xiii

ABSTRACT 1

1 INTRODUCTION 3

1.1 ORIGIN AND DISTRIBUTION 3

1.2 PRODUCTION AND VARIETIES 3

1.3 NUTRITIONAL AND MEDICINAL VALUE 5

1.4 POTATO STORAGE PHYSIOLOGY 6

1.5 VALUE ADDITION 8

2 REVIEW OF LITERATURE 11

2.1 SPECIFIC GRAVITY 11

2.2 STARCH 12

2.3 VITAMINS AND MINERALS 15

2.4 POLYPHENOLS 16

2.5 ANTIOXIDANTS 18

2.6 POLYPHENOL OXIDASE 20

2.7 PER OXIDASES 22

2.8 PACKAGING SYSTEMS 23

2.9 POTATO GREENING 30

2.10 POTATO GLYCOALKALOIDS 33

2.11 LOW TEMPERATURE SWEETENING 35

2.12 SUGAR 37

2.13 POTATO SPROUTING 39

2.14 CHIP COATINGS 44

2.15 ACRYLAMIDE 46

3. MATERIALS AND METHODS 49

3.1 PHASE-I 49

viii

3.2 PHASE-II 49

3.2.1 Packaging Trial 50

3.2.2 Light Trial 51

3.2.3 Temperature Trial 51

3.2.4 Sprouting Trial 52

3.3 PHASE-III 53

3.3.1 Potato Chip Coating 54

3.4 PHYSICO-CHEMICAL AND FUNCTIONAL ANALYSIS OF POTATO 55

3.4.1 Physical Analysis 55

3.4.1.1 Size 55

3.4.1.2 Goemetric mean diameter 55

3.4.1.3 Sphericity 55

3.4.1.4 Surface area 55

3.4.1.5 Tuber counts 56

3.4.1.6 Firmness 56

3.4.1.7 Specific gravity 56

3.4.1.8 Total soluble solids 56

3.4.1.9 pH 57

3.4.1.10 Sprouting 57

3.4.1.11 Weight loss 57

3.4.2 Chemical Analysis 57

3.4.2.1 Dry matter 57

3.4.2.2 Starch 58

3.4.2.3 Protein 58

3.4.2.3 Fat 59

3.4.2.4 Sugar 59

3.4.2.5 Glucose 60

3.4.2.6 Fiber 60

3.4.2.7 Ash contents 60

3.4.2.8 Mineral composition 61

3.4.3 Functional Assays 61

ix

3.4.3.1 Ascorbic acid 61

3.4.3.2 Total glycoalkaloids 62

3.4.3.3 Chlorophyll 63

3.4.3.4 Total phenolic contents 63

3.4.3.5 Radical scavenging activity 64

3.4.3.6 Enzyme estimation 65

3.4.3.6.1Extraction and protein estimation 65

3.4.3.6.2 Polyphenol oxidase (PPO) assay 65

3.4.3.6.3 Per oxidase (POD) assay 66

3.4.4 Potato Chips Evaluation 66

3.5 STATISTICAL ANALYSIS 67

4. RESULTS AND DISCUSSION 68

4.1 PHYSICO-CHEMICAL, FUNCTIONAL AND PROCESSING

ATTRIBUTES OF POTATO VARIETIES 68

4.1.1 Physical Attributes of Potato Varieties 68

4.1.2 Proximate Analysis of Potato varieties 71

4.1.3 Functional Attributes of Potato Varieties 76

4.1.4 Potato Chips Evaluation 78

4.2 EFFECT OF DIFFERENT PACKAGING MATERIALS ON THE

QUALITY ATTRIBUTES OF POTATO 81

4.2.1 Effect on Weight Loss 81

4.2.2 Effect on Total Soluble Solids 85

4.2.3 Effect on pH 87

4.2.4 Effect on Specific Gravity 90

4.2.5 Effect on Glucose 93

4.2.6 Effect on Total Sugars 96

4.2.7 Effect on Starch 98

4.2.8 Effect on Ascorbic Acid 101

4.2.9 Effect on Total Glycoalkaloids 103

4.2.10 Effect on Total Phenolic Contents 106

x

4.2.11 Effect on Radical Scavenging Activity 108

4.2.12 Effect on Polyphenol Oxidase Activity 112

4.2.13 Effect on Peroxidase Activity 115

4.2.14 Effect on Chip Moisture Contents 118

4.2.15 Effect on Chip Fat Absorption 121

4.2.16 Effect on Chip Color 123

4.2.17 Effect on Chip Crispiness 126

4.2.18 Effect on Chip Flavor 128

4.3 EFFECT OF DIFFERENT LIGHT SOURCES ON THE




4.3.3 Effect on Color 135


4.3.5 Effect on Total Sugar 139



4.3.8 Effect on Chlorophyll 146




4.3.12 Effect on Chips Moisture Contents 156





4.4 EFFECT OF DIFFERENT TEMPERATURE STORAGE ON THE


4.4.1 Effect on weight Loss 167



xi










4.4.13 Effect on Chip Moisture Content 199


4.4.15 Effect of Chip Color 204



4.5 EFFECT OF DIFFERENT ANTI SPROUTING AGENTS ON THE




4.5.3 Effect on Sprouting 218

4.5.4 Effect on Specific Gravity 220









4.5.13 Effect on Chip Moisture Content 244



xii



4.6 EFFECT OF INTEGRATED TREATMENTS ON THE QUALITY

ATTRIBUTES OF POTATO 256



4.6.3 Effect on Sprouting 261


4.6.5 Effect on Total Sugar 265

4.6.6 Effect on starch 267







4.6.13 Effect on PerOxidase activity 284

4.6.14 Effect on Chip Moisture Contents 286





GENERAL DISCUSSION 298

CONCLUSIVE SUMMARY 305

RECOMMENDATIONS 311

LITERATURE CITED 312

LIST OF TABLES

xiii

Table No. Page 1a. Physical attributes of potato varieties 69

1b. Correlation between physical attributes 70

2a. Proximate analysis of potato varieties 72

2b. Correlation between proximate components 73

3. Mineral composition of potato varieties 74

4a. Functional attributes of potato varieties 77

4b. Correlation between functional attributes 77

5a. Evaluation of potato chips 79

5b. Correlation between potato chips attributes 80

xiv

LIST OF FIGURES

Figure No

Page

Fig. 1 Weight loss in potato under different packagings showing minimum

loss in polypropylene and LDPE during storage

83

Fig. 2 Total soluble solids in potato under different packagings showing highest

increase in control during storage

86

Fig. 3 pH in potato under different packagings showing maximum retention in

polypropylene and LDPE during storage

88

Fig. 4 Specific gravity in potato under different packagings showing maximum

value in LDPE during storage

91

Fig. 5 Glucose in potato under different packagings showing lowest contents in

polypropylene during storage

95

Fig. 6 Total sugar in potato under different packagings showing lowest contents in

polypropylene and LDPE during storage

97

Fig. 7 Starch in potato under different packagings depicting maximum decline in

control during storage

100

Fig. 8 Ascorbic acid in potato under different packagings showing highest

retention in polypropyleneduring storage

102

Fig. 9 Total glycoalkaloids in potato under different packagings showing highest

increase in control during storage

105

Fig. 10 Total phenolic contents in potato under different packagings showing

maximum retention in polypropylene during storage

107

Fig. 11 Radical scavenging activity in potato under different packagings showing

highest activity in polypropylene during storage

110

Fig. 12 Polyphenol oxidase in potato under different packagings showing lowest

enzymatic activity in LDPE during storage

113

Fig. 13 Per oxidase in potato under different packagings maintaining lowest

enzymatic activity in polypropylene and LDPE during storage

117

Fig. 14 Chip moisture content in potato under different packagings showing

highest increase in control during storage

120

xv

Fig. 15 Chip fat absorption in potato under different packagings showing maximum

value in control during storage

122

Fig. 16 Chip color in potato under different packagings showing highest

value in polypropylene during storage

124

Fig. 17 Chip crispiness in potato under different packagings showing highest

value in polypropylene and LDPE during storage

127

Fig. 18 Chip flavor in potato under different packagings showing highest

value in polypropylene during storage

129

Fig. 19 Weight loss in potato under different light sources showing minimum loss

in dark followed by mercury during storage

132

Fig. 20 Total soluble solids in potato under different light sources showing lowest

increase in dark and green light during storage

134

Fig. 21 Color in potato under different light sources showing highest scores in dark

during storage

136

Fig. 22 Glucose in potato under different light sources showing highest increase in

florescent light during storage

138

Fig. 23 Total Sugar in potato under different light sources showing highest

increase in florescent light during storage

140

Fig. 24 Starch in potato under different light sources showing highest decline in

florescent and red lights during storage

142

Fig. 25 Ascorbic Acid in potato under different light sources showing highest

retention indark followed by green light during storage

145

Fig. 26 Chlorophyll in potato under different light sources showing maximum

increase in florescent and blue lights during storage

147

Fig. 27 Total glycoalkaloids in potato under different light sources showing

highest increase in florescent light during storage

150

Fig. 28 Total phenolic contents in potato under different light sources showing

maximum retention in green light during storage

152

Fig. 29 Radical scavenging activity in potato under different light sources showing

highest activityin dark during storage

155

xvi

Fig. 30 Chip moisture contents in potato under different light sources showing lowe

value in dark during storage

157

Fig. 31 Chip fat absorption in potato under different light sources showing lowest

value in dark during storage

160

Fig. 32 Chip color in potato under different light sources showing highest value in

dark and green light during storage

162

Fig. 33 Chip crispiness in potato under different light sources showing highest scor

in dark and green light during storage

164

Fig. 34 Chip flavor in potato under different light sources showing highest scores


166

Fig. 35 Chip flavor in potato under different light sources showing highest scores


168

Fig. 36 Total soluble solids in potato under comparative temperature storage

showing maximum increase at 5oC

171

Fig. 37 Glucose in potato under comparative temperature storage showing maximu

contents at 5oC

174

Fig. 38 Total sugar in potato under comparative temperature storage showing

maximum contents at 5oC

176

Fig. 39 Starch in potato under comparative temperature storage maintaining


179

Fig. 40 Ascorbic acid in potato under comparative temperature storage

maintaining maximum retention at 5oC

182

Fig. 41 Chlorophyll in potato under comparative temperature storage maintaining


185

Fig. 42 Total Glycoalkaloids in potato under comparative temperature storage

showing lowest contents at 5oC

187

Fig. 43 Total phenolic contents in potato under comparative temperature storage

showing maximum retention at 5oC

189

Fig. 44 Radical scavenging activity in potato under comparative temperature

storage showing highest activity at 5oC

192

Fig. 45 Polyphenol oxidase in potato under comparative temperature storage 195

xvii

showing lowest enzymatic activity at 5oC

Fig. 46 Per oxidase in potato under comparative temperature storage showing lowe

enzymatic activity at 5oC

198

Fig. 47 Chip moisture content in potato under comparative temperature storage

showing highest contents at 25oC

200

Fig. 48 Chip fat absorption in potato under comparative temperature storage

showing highest value at 25oC

203

Fig. 49 Chip color in potato under comparative temperature storage showing highes

value at 15oC

205

Fig. 50 Chip crispiness in potato under comparative temperature storage showing

highest value at 15oC

208

Fig. 51 Chip Flavor in potato under comparative temperature storage showing high

value at 15oC

210

Fig. 52 Weight loss in response to different sprout inhibitors showing minimum

loss in CIPC during potato storage

213

Fig. 53 Total soluble solids in response to different sprout inhibitors showing

maximum increase in control during potato storage

217

Fig. 54 Sprouting in response to different sprout inhibitors showing maximum

percentage in control during potato storage

219

Fig. 55 Specific gravity in response to different sprout inhibitors showing lowest

value in control during potato storage

222

Fig. 56 Glucose in response to different sprout inhibitors showing highest

increase in control during potato storage

224

Fig. 57 Total sugar in response to different sprout inhibitors showing highest

increase in control during potato storage

226

Fig. 58 Starch in response to different sprout inhibitors showing maximum

contents in CIPC and clove during potato storage

229

Fig. 59 Total glycoalkaloids in response to different sprout inhibitors showing

lowest increase in CIPC and clove during potato storage

231

Fig. 60 Total phenolic contents in response to different sprout inhibitors showing

maximum retention in CIPC and clove during potato storage

234

xviii

Fig. 61 Radical scavenging activity in response to different sprout inhibitors

showing highest activity in CIPC and clove during potato storage

237

Fig. 62 Polyphenol oxidase in response to different sprout inhibitors showing

lowest enzymatic activity in CIPC and clove during potato storage

239

Fig. 63 Per oxidase in response to different sprout inhibitors showing lowest

enzymatic activity in CIPC and clove during potato storage

242

Fig. 64 Chip moisture contents in response to different sprout inhibitors showing

highest contents in control during potato storage

245

Fig. 65 Chip fat absorption in response to different sprout inhibitors showing

highest contents in control during potato storage

248

Fig. 66 Chip color in response to different sprout inhibitors showing highest

scores in CIPC and clove during potato storage

250

Fig. 67 Chip crispiness in response to different sprout inhibitors showing highest


252

Fig. 68 Chip flavor in response to different sprout inhibitors showing highest


255

Fig. 69 Weight loss in response to integrated treatment showing minimum loss as

compare to control during storage

257

Fig. 70 Total soluble solids in response to integrated treatment showing lower

contents as compare to control during storage

260

Fig. 71 Sprouting in response to integrated treatment showing lower percentage

as compare to control during storage

262

Fig. 72 Glucose in response to integrated treatment showing lower contents as


264

Fig. 73 Total sugar in response to integrated treatment showing lower contents as


266

Fig. 74 Starch in response to integrated treatment maintaining higher contents as


268

Fig. 75 Ascorbic acid in response to integrated treatment maintaining higher 271

xix


Fig. 76 Chlorophyll in response to integrated treatment maintaining lower


273

Fig. 77 Total Glycoalkaloids in response to integrated treatment maintaining

lower contents as compare to control during storage

275

Fig. 78 Total phenolic contents in response to integrated treatment maintaining

higher contents as compare to control during storage

278

Fig. 79 Radical scavenging activity in response to integrated treatment

maintaining higher activity as compare to control during storage

280

Fig. 80 Polyphenol oxidase in response to integrated treatment showing lower

enzymatic activity as compare to control during storage

283

Fig. 81 Per oxidase in response to integrated treatment showing lower enzymatic

activity as compare to control during storage

285

Fig. 82 Higher Chip moisture content in potato chips due to aloe vera (A.V)

coatings as compare to control

287

Fig. 83 Higher Chip fat absorption in potato chips due to aloe vera (A.V)

coatings as compare to control.

290

Fig. 84 Comparision of Chip color in response to aloe vera (A.V) coatings on

potato chips

292

Fig. 85 Comparision of Chip crispiness in response to aloe vera (A.V) coatings

on potato chips

294

Fig. 86 Comparision of Chip flavor in response to aloe vera (A.V) coatings on

potato chips

296

ABSTRACT

Agro ecological diversity and favorable environment have enabled Pakistan to

harvest bulk of potato crop however facing problems of poor post harvest management

practices and unavailability of superior raw material for the potato processing industry.

A comprehensive study was planned to identify best packaging material and

appropriate storage conditions for the premium potato variety. The present study has

been divided in to three different phase to address specific objectives. The first phase

of study encompasses physico-chemical, functional and processing attributes in

prominent potato varieties. The selected variety was subjected to different post harvest

storage conditions along with their processing parameters analysis in second phase of

the study. The last phase of study evaluated the storage stability of premium variety

under best results identified in the second phase. In the first phase of study, physical

attributes (tuber size, geometric mean diameter, sphericity, surface area, firmness,

specific gravity, total soluble solids, pH, sprouting %, tuber color) Chemical attributes

(dry matter, starch, protein, fat, sugar, fibre, ash and predominant minerals) functional

attributes (ascorbic acids, glycoalkaloids, total phenolic contents, radical scavenging

activity) and processing performance (chip moisture contents, fat absorption, color and

sensorial attributes) were evaluated in ten commercial varieties i.e. Agria, Atlantic,

Cardinal, Chipsona, Courage, Desi, Desiree, Hermes, Lady Rosetta, and Satellite. In

general Lady Rosetta followed by Hermes was the most appreciable variety regarding

their physical attributes. Lady Rosetta followed by Atlantic attained maximum dry

matter and starch contents. Least sugar contents were recorded in Agria and maximum

fat and protein contents were quantified in Desiree. In general; functional attributes

were found maximum in Desi followed by Desiree. A promising correlation was

estimated between most of these parameters with distinctive correlation (R=0.903)

identified between total phenolic contents and radical scavenging activity. Post

processing parameters like moisture contents, fat absorption, and sensory evaluation in

Lady Rosetta showed its preference over all other varieties followed by Hermes. In the

second phase variety” Lady Rosetta” was evaluated under different storage conditions

1

2

(packaging, light, temperature, and anti sprouting agents) on the basis of transition in

their quality attributes (reported in 1st phase) and enzymatic (polyphenol oxidase,

peroxidase) activities. Potatoes were stored under different packaging materials (jute,

nylon, polypropylene, cotton, low density polyethylene, medium density polyethylene,

high density polyethylene) at ambient temperature (25±2oC). Results revealed that

polypropylene packaging and low density polyethylene packaging were found best and

maintained tubers quality attributes up to 63 days, while other packaging materials

were also found effective as compare to control. Thirty days storage of tubers under

different illuminations (blue, fluorescent, green, mercury, red, dark) at ambient

temperature (25 ±2oC) was carried out. Potato tubers kept under dark presented

minimum loss of quality parameters however green and mercury lights posed best

storage performance over all other illuminations during one month. Tubers were found

highly susceptible to fluorescent light with poor processing attributes were recorded in

red and blue light exposures. Results under comparative temperature regimes (5, 15

and 25oC) showed maximum storage stability up to 126 days under 5oC, however

associated with low enzyme activity, elevated sugars contents in tubers and poor

processing performances in fried chips. Exposing tubers to different anti sprouting

agents (hot water treatment, spearmint oil, clove oil, CIPC) showed that CIPC and

Clove oils applications were found significant in preventing tuber sprouting at the end

of 80 days storage. In general, both retained superior tuber characters with remarkable

processing characters during the storage period. Tuber dormancy was ensured under

both treatments till the end at ambient temperature (25 ± 2oC) storage. In the last phase

integrated post harvest management of potato variety “Lady Rosetta” on the basis of

best results identified in second phase ensured tuber dormancy and prolonged storage

life up to 180 days with appreciable retention of tuber quality attributes and superior

processing performance as compare to 100% sprouting observed in control on the 80th

day of storage. Coating of potato chips with 20% aloe vera gel presented best results

with reduced fat uptake along with appreciable sensorial scores.

3

Chapter 1

INTRODUCTION

Potato (Solanum tuberosum) belongs to solanaceae family and is a

perennial plant, which is herbaceous in nature. The plant however is grown in

Pakistan annually and its propagation is carried out through tubers, which are thick

puffy part of the rhizome found underground and covered by modified eyes and

buds. The climatic requirements of potato are cool and moist but frost brings

mechanical injury, which is detrimental for the crop. The stem tuber is the edible

part of the crop which serves as an energy reservoir and commonly employed for

vegetative propagation purpose. Botanically potato tuber is an extension of stolon

arising from the buds at the base of stem (Beukema and Vander-Zaag, 1990).

1.1 ORIGIN AND DISTRIBUTION

Potato is native to several countries of Latin American continent like Peru,

Chile, Bolivia, Argentina, Colombia etc. It is believed that the cultivated potato

was derived from the feral species found in South America, particularly in the

Andes of Peru and Bolivia. The crop is introduced in the European continent

through Spain and then into England. The wide spread of this crop through out the

world is witnessed during the start of 17th century into different British colonies

like Ireland, Scotland, United states and Indo-Pak subcontinent (Hawkes, 1978).

1.2 PRODUCTION AND VARIETIES

Potato is number one non-grain food crop in the world and one third of the

total production is being harvested in densely populated developing countries, like

3

4

China and India, and thus alleviates the food crisis in third world countries (PIC,

2008). It is ranked top most important crop in South American continent, second

most important crop in Europe and fourth on the Globe after wheat, rice and maize

(Messer, 2000). The overall estimated yield of potato in the world is about 320.67

million tons and China being the major contributor produces 72 million tons

followed by Russian Federation and India with yield of 35.7 and 26.2 million tons

respectively. The demand for potato in the international market is one the rise and

all the major exporting countries are trying to increase the yield and as a reciprocal

increase their share in world market (FAO, 2007).

Potato is the most imperative and widely cultivated vegetable crop in

Pakistan with an estimated 2.5 million tons production from an area of 150

thousand hectare. Punjab province produces the lion’s share of potato crop

contributing 90% and the rest of the three provinces produce 10 % of the total

potato produce of Pakistan in an order of Khyber Pakhtun Khwa being a leading

producer followed by Balochistan and Sindh (GOP, 2009). The overall availability

in world market is however below par and Pakistan contributes only around 1% in

world production. Despite significant area under cultivation and multiple growing

seasons the annual export remained only 50,000 tons contributing 0.5% of the

world export. The main potato export markets are Sri Lanka and Afghanistan

(PHDEB, 2008)

Potato carries broad biodiversity, with more than 4000 known varieties

most of which belong to the species Solanum tuberosum consumed in 150

countries of the world (Burlingame et al., 2009). Few of the most recognized

varieties of potato in Pakistan are red skinned (Desiree, Courage, Cardinal,

Kuroda, Lady Rosetta, Raja, etc.) and white skinned (Agria, Hermes, Chipsona,

5

Satellite, Sante, Diamont, etc.), which are produced on large scale across the

country and consumed for processing and table use (PHDEB, 2008).

1.3 NUTRITIONAL AND MEDICINAL VALUE

The world wide consumption of potatoes is ascribed to its lusciousness and

high nutritive value (Rytel et al., 2005). It produces more dry matter per hectare

than the major cereal crops like wheat, rice etc (Gravoueille, 1999) thus considered

as an important staple crop in most parts of the world. Potatoes are a rich source of

carbohydrate with starch being the key ingredient or the main form, which serves

as an inexpensive source of energy (Lachman et al., 2001). In addition it is also

considered as good source of high-quality protein such as lysine (Friedman, 2004).

One hundred grams of potato provides 90 kilocalories energy containing vital

constituents like water 75.0 grams, carbohydrates 19.0 grams , fat 0.1grams,

protein 2.0 grams, Thiamin (Vit.B1) 0.08 mg, Riboflavin (Vit.B2) 0.03 mg, Niacin

(Vit.B3) 1.1 mg, Vitamin B6 0.25 mg, Vitamin C 20.0 mg, Calcium 12.0 mg, Iron

1.8 mg, Magnesium 23.0 mg, Phosphorus 57.0 mg and Sodium 6.0 mg. (Raban et

al., 1994).

Four of the six main vitamins required in our daily diet are present in

potatoes, which speak highly of the nutritious importance of the crop. The vitamins

found in potatoes are ascorbic acid, thiamin, riboflavin and niacin. Among others

ascorbic acid is the main vitamin present as dietary antioxidant, which is

vulnerable against heat and light thus considered as major index of quality

deterioration duration storage (Burlingame et al., 2009). In addition potatoes are

the second most imperative source of vitamin B6 for the elderly who are

particularly at risk of chronic diseases. Vitamin B6 influences hormonal synthesis,

erythrocyte production, immune modulation and central nervous system functions.

6

In addition is also important against treatment of various chronic diseases such as

sickle cell anemia, asthma, and cancer (Kolasa, 1993). Potato is low cholesterol,

high potassium food with significant antioxidants potential thus capable of

protecting human beings against cardiovascular diseases and cancer (Lachman et

al., 2000). Polyphenol in addition are the most common dietary antioxidant

(Lachmann et al., 2008) being efficient as reducing agents, metal chelators and

reactive oxygen species quenchers in biological system.

1.4 POTATO STORAGE PHYSIOLOGY

Potato tuber undergoes physiological dormancy period during the

postharvest storage. The length of the dormancy period is dependent on the

varietal genetic profile, environmental factors and storage conditions. Commercial

potato cultivars grown for the processing industry have shorter dormancy periods

and associated with different storage disorders like sweetening, greening, toxicity

etc; therefore it is obligatory to employ suitable storage conditions to ensure their

continuous supply (Suttle, 2007). It is literally impossible to prevent potato tubers

from light exposure during the marketing chain and commercial processing. The

response however, presents remarkable changes in the physiology of the potato

tuber and deteriorates its quality by either inducing sweetness or sprouting or any

other morphological change. Such undesirable changes also include tuber

greening due to excessive chlorophyll accumulation and formation of toxic

steroidal glycoalkaloids.

Glycoalkaloids are present as alpha-solanine and alpha-chaconine in

marginal tuber layers however with the increased amassing of the compounds,

significant economic losses coupled with food safety hazards are observed.

Presently high glycoalkaloids (GA) intake considered as grave food safety concern

7

and with the increasing demand for fresh and processed potatoes the threat has

increased manifold (Percival, 1999). Excessive glycoalkaloids accumulation leaves

bitter taste if the concentration goes past a specific level with upper safe intake

limit for human is 20 mg/100g f.w (Nema et al., 2008). Excessive glycoalkaloids

intake result in diarrhea, vomiting, fever, rapid pulse, colic pain, low blood

pressure, gastroenteritis, and neurological disorders (Slanina, 1990). Although

abundant chlorophyll formation in potatoes is not serious threat for human body

but green potatoes appear to be highly unattractive in comparison to normal red

skinned or white skinned potatoes. The unappealing green color of the potatoes

reduce their market value and according to a research carried out by British potato

council, £ 6 million loss has been borne by the grower due to its green

pigmentation (Anon, 1998).

The efficient sprout control is necessary to maintain effective tuber quality

and minimal storage losses. Sprouting can increase tuber weight loss primarily due

to rapid evapotranspiration through the lenticels and leads to elevated reducing

sugar level (Hartmans et al. 1995). In addition, sprouted tubers are ascribed to the

elevated levels of toxic glycoalkaloids (Friedman, 2006). Sprouting in potato can be

controlled by using different sprout inhibitors like CIPC (Fauconnier et al., 2002),

Sprout suppressants like essential oils (Kleinkopf et al., 2003), irradiations (Rezaee

et al., 2011) pressure application (Saraiva et al., 2011 ) and hot water treatments

(Kyriacou et al., 2008).

Potato is semi perishable crop however placed under low temperature

storage to prevent them from sprouting and to ensure their regular supply

whenever required. Low temperature potato storage is however associated with

8

low temperature sweetening and is specifically undesirable in processing potato

varieties (Kyriacou et al., 2009). The phenomenon is primarily associated with the

potato storage under low temperature and as a result of which the insoluble starch

is enzymatically hydrolyzed into soluble glucose, fructose and sucrose

(Sowokinos, 1990). Tuber sweetening deteriorates tuber commercial quality and

causes the fried products to turn brown and bitter in taste due to subsequent

acrylamide formation. Acrylamides are toxic compounds produced in the fried

potato products as a by-product of the maillard reaction in the presence of major

precursors like reducing sugar (glucose) and the amino acid (asparagines)

(Mottram et al., 2002).

1.5 VALUE ADDITION

Potato value addtition includes different commercial preparations like

potato chips, mashed potatoes, steamed potato, potato patties, whole baked

potatoes, potato flakes and dehydrated potato granules. Commercial production of

alcoholic beverage and adhesive in manufacturing industries are also some of the

other uses of this important crop especially in developed countries. Potato is one of

the very few vegetables with lot of serving variations which can both be served hot

as potato chips and cold as potato salad without losing its peculiar taste. Another

important dish is mashed potatoes in which the potatoes are boiled, peeled and

served after mashing them with milk, yogurt or butter (Christine, 1996). However

the most important one being the potato chips which gained terrific economic

value in processed food industry. The most important among snack products is

discovered back in 1853 by George Crum an American Chef, and gained

tremendous popularity in processed food industry. Currently, Potato chips

contributes major share in the snack food market of the world and generated total

9

revenues of US$16.4 billion in 2005 (www.Potatopro.com) and the consumption of

this important snack exceeds 1.2 billion pounds per year in United States (Clark

2003).

Reduction of post harvest losses is an area of grave concern and several

loss reduction techniques have been developed over time, which not only limit the

post harvest losses but also improve the quality of horticultural commodities. Low

and high temperature, modified atmosphere, controlled atmosphere, hypobaric

storage, irradiation etc. are few of the physical methods to achieve the objective of

reduction of post harvest losses and final quality maintenance. The chemical

methods used for this purpose include waxes, edible coatings, fungicides, ethylene

absorbents, senescence retardants etc.

Several varieties of potato have been developed and released to the farmers,

even though these varieties exhibit appreciable tuber characteristics, the

comprehensive data regarding their proximate composition, mineral contents,

functional potential and processing performance under local ecological condition

(weather, soil, irrigation) were mainly unknown. In addition appropriate

postharvest management of this very important crop is desirable to fetch premium

share in the International market. Few of the appropriate measures include on farm

low cost storage, hydrocooling, modified atmosphere packaging and

waxing/coating. One of the major pre requisites before marketing of the produce is

sorting, grading followed by quality oriented packaging according to international

standards. The horticultural commodities have a short shelf life and the improved

post harvest management techniques involving proper sorting, grading, packaging,

labeling and transportation through the supply chain not only increases the shelf

life but also brings material gains to the farmers. In this regard approprate storage

10

conditions (Temperature, Light) along with the suitable sprout inhibitor are needed

to be identified in order to conserve the commericial value and to enhance the

storage stability of this important crop. A comprehensive study is therefore

designed with following objectives addressed in different section of this

manuscript:

1. To analyze different Physico-chemical, functional and processing attributes

of some important potato varieties grown in Pakistan.

2. To identify the suitable packaging material for the premium variety

3. To establish appropriate storage temperature for the selected potato variety

4. To evaluate the best light source for the selected variety

5. To investigate the best sprout control under storage period.

6. To establish integrated management system to asses the storage life of

selected potato variety.

11

Chapter 2

REVIEW OF LITERATURE

Potato is gradually becoming one of the most important crops both for the

farmers and the consumers in Pakistan. The production volume places it at number

four amongst major crops of Pakistan and its high nutritive value and yield gives it

an additional value. At the time of independence the area under potato was about

three thousand hectares and the yield obtained from the cultivated area was about

thirty thousand tons (Malik, 1995). The scenario has gradually changed over the

years and in the last few decades it has become Pakistan’s fastest growing staple

crop. Presently 2.5 million ton production of potato can easily address the issue of

food security for the expanding population of Pakistan (GOP, 2009).

Potato being important cash crops with substantial exportable potential can

improve farm incomes and foreign exchange earnings for the country. Major

varieties that have been cultivated in Pakistan for table and processing purpose are

of Dutch origin and physiochemical evaluation of these varieties under indigenous

environmental conditions is very important to identify their potential in growing

market for table and processed consumption (PHDEB, 2008).These attributes

defines the economic importance of these varieties and establish their ultimate use.

The present study investigated transition in different quality attributes of potato in

response to different packaging systems and storage conditions.

2.1 SPECIFIC GRAVITY

Specific gravity is one of the most important tools for the quality

evaluation of potato variety and is largely associated with the presence of its dry

matter or total solid contents. The correlation between specific gravity and

11

12

processing quality of potato is eminent (Komiyama et al., 2007), and the potato

processing industry for the production of chips and French fries mostly depends

on the specific gravity for the acceptable quality of processed products (Haynes,

2001). Gould, (1999) reported that for an every 0.005 increase in specific gravity

an approximate increase of one percent in the chip yield is achieved, thus enables

the processor to find and select tuber of high solid content with minimum effort

and time.

Specific gravity varies between different potato varieties as some are

intrinsically of high total solid contents. Under comparable growing conditions

certain varieties are consistently high in dry matter contents such disparity has

also been reported by previous researchers (Lefort et al., 2003). Different methods

has been developed to determine the specific gravity in potato varieties like,

hydrometer (Snack Food Association, 1991) brine solution (Lusas and Rooney,

2001) weight of potatoes in air and water (Kumar et al., 2005) etc. Specific

gravity affects the oil uptake in the processed potato products like Chips, French

fries etc (Sinha et al., 1992). Potato varieties with a high specific gravity have

been revealed to produce a high yield of chips with low oil uptake (Kita, 2002). A

positive relationship between specific gravity and oil uptake in thin sliced sweet

potato crisps has also been reported by Hagenimana et al. (1998).

2.2 STARCH

Starch is the most important caloric nutrient and contributing 70-80% of the

dry matter of the potato which accounts to its close correlation with the specific

gravity and dry matter contents. The two main components of starch i.e Amylose

and Amylopectin are present in the ratio of 1:3 (Salunkhe and Desai, 1984). The

sugar produced in the leaves of potato plants are translocated to the growing tissues

13

where they are converted into starch which is primarily mediated through the

polymerization activities of starch synthetase enzyme (Fernie et al., 2002). The

energy requirement of dormant potato tuber during post harvest storage and

sprouting initiation is largely dependent on this polymerized starch. Biemelt et al.,

(2000) reported that sprouting in stored potato is largely dependent on the

hydrolysis of starch content, which offer substantial energy for the growth and

development of sprouts.

Potato processing and other related industries require examination

concerning starch quality and dry matter (DM) contents of potato tubers. Haase,

(2003) reported the Coefficients values (R2) for dry matter and starch

concentration respectively were 0.92 and 0.83 (starch concentration involving 14

and 24%), and 0.94 and 0.88 (starch concentration ≥14%). In addition both

constituents were checked by near infrared spectroscopy. (R2 justification set was

0.98 and 0.97 for dry material and starch concentration, correspondingly). He

concluded the effectiveness of near infrared technique with a reduced amount of

deviation than the under-water weighting techniques.

Liu et al. (2003) determined physico-chemical properties of starch isolated

from three potato cultivars (Snowden, Shepody and Superior) during development.

Various analytical techniques like Differential scanning calorimetry for

retrogradation and gelatinization, Structure of crystalline starch by X-ray

diffraction method and Rapid viscosity analysis for starch glue viscosity and

pasting temperature were carried out. The content of starch of potato tubers

showed a great variation during its growth with maximum around 2–3 months.

Shepody and Snowden had high starch content as compared to Superior; X-ray

14

diffraction model of starch granule remained unchanged during potato

development time. Starch of Shepody cultivar showed peak absolute viscosity,

maximum temperature and smaller value of enthalpy of gelatinization and

retrogradation. Minimum growth time of potatoes caused lower swelling, elevated

amylose concentration and top gelatinization temperature, pasting temperature and

finishing viscosity of starches.

Casanas et al. (2009) studied eight different cultivars and three

species/subspecies like Solanum x chaucha, Solanum tuberosum spp. tuberosum

and spp. andigena were harvested in Tenirife and evaluated for their proximate

composition. The study revealed lot of variations in all cultivars and

species/subspecies with respect to its chemical analysis. Mean values for moisture

contents showed a lot of variation among the three species/subspecies under study.

Potatoes belonging to spp. tuberosum revealed high level of moisture content as

compared to S. x chaucha, and higher level in latter than the spp. Andigena. Local

potatoes were smaller in size with lower moisture contents and higher nutritional

level. Study concluded negative correlation between starch and moisture contents.

LDA analysis showed significant differences between local and newly imported

potato varieties.

The textural attributes in tubers like consistency, mealiness, sloughing etc

are largely associated to its starch properties and subsequently changes during the

processing. Kita, (2002) identified the relationship between chip texture and

starch, non-starch polysaccharides. Amongst five tested varieties, Saturn’’ and

‘‘Panda’’ varieties exhibited best texture in crisps owing to its palpable starch

and non starch contents.

15

2.3 VITAMINS AND MINERALS

In addition to significant carbohydrates and quality proteins contents

(Friedman, 2004), potato provides a substantial contribution to the daily supply of

vitamins and minerals. They are significant source of minerals like potassium,

phosphorous, calcium etc. (Andre et al., 2007) and their value in the human diet is

highly appreciated as a prime source of ascorbic acid (Dale et al., 2003). Vitamin

C is the predominant vitamin present in potato and of significant functional

importance (Davey et al., 2000). It acts as a natural antioxidant by donating

electrons and scavenging free radicals thus preventing cellular damage inside the

biological system (Padayatty et al., 2003). It aids in collagen production, facilitate

iron absorption, promote wounds healing, and maintain healthy gums eventually

improve the overall immune system (Goggs et al., 2005). During post harvest

storage of fruits and vegetables ascorbic acid known to be effected by factors like

light, heat, oxygen, prolonged storage, mechanical damage, chilling injury, relative

humidity, variety, soil type, physiological stages etc. (Lee and Kader, 2000).

Ascorbic acid is known to be powerful natural antioxidant being capable of

deactivating reactive oxygen species by conjugation with other antioxidant as in

ascorbate-glutathione cycle (Jimenez et al., 1996). It also prevents enzymatic

browning in fruits and vegetables by the reduction of quinones back into phenolic

substrates (Robert et al., 2003) however oxidized itself into dehydro-ascorbic acid

(Padayatty et al., 2003). It have also been used in different food preparations for

the prevention of enzymatic browning, color retention and effective post harvest

application for storage life extension.

Potato being low fat food is also being considered as an imperative source

of vitamins A and B (Lachman et al., 2000). They are the second most important

16

contributor of vitamin B6, which involved in amino acid, nucleic acid, glycogen,

and lipid metabolism and thus regulates immune modulation, erythrocyte

production, and neural functions (Kant and Block, 1990). It also plays role in the

treatment of various chronic diseases such as sickle cell anemia and cancer

(Kolasa, 1993). Potassium is a predominant mineral found in the potato tuber

(Yilmaz et al., 2005). It helps to regulate inter and intra cellular fluids and mineral

balance thus helps to overcome hypertension in patients. In addition also found

vital in transmitting nerve impulses and helping muscular contraction.

2.4 POLYPHENOLS

Polyphenols are the commonly occurring secondary plant metabolites

primarily associated with the antioxidant activity as verified by in-vitro lipid

oxidation model (Kaur and Kapoor, 2002). More than 8000 phenolic structures

have been indentified so far being as simple as phenolic acid to highly complex

tannins (Harborne, 1998). They are synthesized in the plant metabolism through

shikimate pathway and acetate pathway (Bravo, 1998). Phenolics are vital for plant

development, reproduction and connected to diverse role such as protein synthesis,

enzyme biosythesis, anti-pathogen, anti tumour and aids in the detection of

symbionts. They also protect live plants against oxidative stress and promote

healing (Shahidi and Naczk, 1995).

Phenyl alanine acts as precursor in phenol biosynthesis, primarily mediated

through the activity of Phenylalanine Ammonia Lyase (PAL) which catalyses the

deamination of phenylalanine (Hamauzu, 2006). Phenolics exist in diverse

configuration as free, glycosylated, polymerized forms (Naezk and shahidi, 2004)

however the basic compositional feature of phenolics is diphenyl propane moiety

that comprises of two aromatic rings linked through three carbon atoms forming an

17

oxygenated heterocycle i.e; phenol subunit (Teixeira et al., 2005). They are present

either as simple phenols (one phenol sub units), poly phenols (two phenol subunits)

or tannins (three phenol subunits). Phenolic acid is the carboxylic derivative of

phenol which is also associated with the sensory attributes and antioxidant

potential in foods (Robbins, 2003).

Polyphenols have strong antioxidant potential in neutralizing and

quenching free radicals by donating electrons and forming phenoxyl radicals which

are relatively inert and do not instigate further radical reactions (Fernandez et al.,

2004). They act as terminator of free radicals and chelator of metal ions capable of

lipid peroxidation (Schroeter et al., 2002). Milde et al. (2007) reported that

polyphenols along with carotenoids prevent the oxidation of Low Density

Lipoproteins thus preventing from atherosclerosis and related disorders. Owing to

its significant antioxidant capacity the role of phenolics in human health is

increasingly being realized. The protective effect of diet rich in fruits and vegetable

against degenerative diseases is largely attributed to the presence of phenolic

compounds (Manach et al., 2005). Regular intake of diet rich in phenolics has been

linked to lower rate of cancer and cardiovascular diseases (Seeram et al., 2005).

Considerable diversity of phenolic compounds present in potato tubers having

major phenolics as gallic acid, chlorogenic acid, caffeic acid (Niggeweg etal.,

2004) while minor includes ferulic acid, rutin, quercetin, kaempferol etc. (Nara et

al., 2006). In addition purple and red fleshed potato varieties also includes

petunidin, p-courmaric, pelargonidin (Reyes, 2005). Despite having moderate

phenolic contents potato exhibited potato exhibited the second best inhibitory

action on low density lipoprotein oxidation between 23 different vegetables studied

(Vinson et al., 1998).

18

2.5 ANTIOXIDANTS

Antioxidants are the compounds which have the capacity to quench free

radicals and protect the biological systems against their potential detrimental

effects (Diplock, 1998). Free radical produced in the biological system due to

different physiological processes like oxidative stress, senescence etc induces

loss of nutritional quality of fruits and vegetable during post harvest storage

(Antolovich et al., 2001). Oxidative stress induced by these free radicals in the

form of super oxide anions (O-2), Hydrogen peroxide (H2O2) and Hydroxyl

Radicals (OH-) considered to be the key factors in various degenerative diseases.

Free radicals are the molecules having one or more unpaired electron which confer

them considerable degree of reactivity. They are omnipresent and generated in

normal physiological processes like respiration, pathogenic activity, inflammatory

cell activations, mutations etc. (Hussain et al., 2003).

Free radicals are present either as reactive nitrogen species (RNS) or

reactive oxygen species (ROS) and capable of damaging extensive range of

oxidizable substrates like DNA, Proteins, Lipids, and Carbohydrates (Haila, 1999).

Reactive oxygen species (ROS) can physiologically transform DNA, producing

single/ double-stranded DNA fragments, base or sugar modifications, hold or

stimulation of transcription, and genomic instability (Poli et al., 2004). Reactive

nitrogen species (RNS) like nitrogen oxides and peroxynitrites have also been

involved in DNA modifications. In addition, different redox metals capable of

producing free radicals, and non-redox metals having potential to bind critical

thiols, facilitates the mechanism of carcinogenesis (Leonard et al., 2004). Valko et

al. (2001) observed that ferous-induced stress is believed to be a primary cause of

human colorectal cancer. The production of ROS and RNS inside the biological

19

system leads to the chemical modifications of important macromolecules. Anti

oxidants have the capability to avoid such modifications and avert the beginning of

oxidizing chain reactions (Velioglu et al., 1998). They quench free radicals by

conferring electron or hydrogen, neutralizing the singlet oxygen and deactivation

of metal ions (Shahidi, 2002).

Antioxidants are broadly classified as non enzymatic (free radical

scavengers like ascorbic acids, phenolics, flavonoids, tocopherols) or

enzymatic (inhibit peroxidase reactions like superoxide di-mutases,

glutathione peroxidases) in nature (Nzaramba, 2007). On the basis of their origin

they are characterized as synthetic or natural. Butyl hydorxy toluene (BHT) and

Butyl hyroxy anisole (BHA) are the examples of synthetic antioxidants having

phenolic structures with different alkyl substitution. However the uses of these

synthetic antioxidants are assumed to cause carcinogenity thus being restricted to

use in food stuff (Koleva et al., 2002). Thus need arises to replace these synthetic

antioxidants with naturally occurring antioxidants. Natural antioxidants constitutes

wide range of compounds like, phenolic compounds (Flavonoids, phenolic acids,

gallic acids, anthocyanins), nitrogen compounds (alkaloids, amines, amino acids),

Carotenoids, Ascorbic acids, tocopherols etc (Shahidi, 2002). Most of these

antioxidants are of food origin and termed as dietary antioxidants.

Significant antioxidant activity has been identified in the peel (Singh and

Singh, 2004) and flesh (Lachman et al., 2008) of potato and thus considered to be

an important source of dietary antioxidants. Being major staple crop in most part of

the world utilization of potato as an alternate source of synthetic antioxidant will

be very effective against different chronic disorders. Their regular intake of dietary

antioxidants can prevent from diabetes, cardiovascular diseases, carcinogenesis,

20

neurological disorder and ageing (Makazan et al., 2007). Highest anti oxidant

activity has been estimated in purple skinned varieties followed by moderate

and lowest activity recorded in red skinned and yellow skinned potato

varieties respectively (Li et al., 2006).

Antioxidant assays largely depends on their effects through different

mechanism and specified functions. Different assays have been developed to

measure the antioxidant activity. Their mode of action is either as electron transfer

reaction based assay and hydrogen atom transfer reaction based assay. Electron

transfer reaction based assays include trolox equivalence antioxidant capacity

(TEAC), ferric ion reducing antioxidant power (FRAP), 3-ethyl-benzothiazoline-6-

sulfonic acid (ABTS) and 2, 2 Diphenyl -1-picryl hydrazyl (DPPH). Hydrogen

atom transfer reaction based assays are total radical trapping antioxidant parameter

(TRAP) and oxygen radical absorbance capacity (ORAC) (Huang et al., 2005).

The most frequently used assays are DPPH and ABTS radicals because of their

simplicity, swiftness and sensitivity (Arnao et al., 1999).

2.6 POLYPHENOL OXIDASE (PPO)

Enzymes are necessarily required in cellular metabolism for regulating key

biochemical reactions and their working mechanism is required for understanding

the chemical basis of life. They lower down the activation energy required for the

particular biochemical reaction and facilitate the formation of enzyme-substrate

complex. Being biological catalysts they are highly specific, usually required in

small amount and their activity is measured by the quantity of reaction product.

Polyphenol Oxidase (PPO) is also called as phenol oxidase, tyrosinase,

catechol oxidase, mono phenol oxidase and diphenol oxidase. Enzymatic browning

21

initiated in fruits and vegetables due to multiple reasons like mechanical injuries

(cutting, wounding and bruising), storage disorders (chilling and freeze injuries) or

by physiological reasons (ripening and senescense) (Crumiere, 2000). PPO activity

increases with the increase in physiological stages and becomes highly pronounced

during senescence, and under stress conditions. Thus the activity is the significant

index of post harvest storage life in horticultural produce.

Enzymatic browning causes nutritional and sensorial loss in horticultural

commodities and primarily mediated through the activities of the group of enzymes

termed as Poly phenol oxidases (Anthon and Barrett, 2002). These enzymes

catalyze reaction between colourless polyphenol molecules (Catechol) and

molecular oxygen forming orange coloured benoquinone which spontaneously

cause the formation of dark coloured complex called Melanins (Ding et al., 1998).

The polyphenol oxidase (PPO) activity using catechol (polyphenol) as substrate is

described as under:

Catechol + Oxygen ----------- Benzoquinone + water ------------- Melanin

The formation of dark colored pigment (melanin) however, confers

antimicrobial properties to the fresh produce and their colour intensity is reliant on

the kind of substrate and environmental conditions (Nicolas et al., 1994).

Polyphenols are present in fruits and vegetables in diverse forms like Gallic acid,

flavonols, benzoic acid, cinnamic acids, chlorogenic acids etc. and most of them

acts as substrate for polyphenol oxidase activity (Crumiere, 2000). Yemenicioglu,

(2002) reported that polyphenol oxidase activity can be controlled in Russet

Burbank potatoes by mild heat treatment at 50oC. He reported significant reduction

(25-45%) in enzyme activity with appreciable sensorial parameters while

22

blanching at above temperature for 60 minutes. The technique have been found as

better alternative to sulphitation for browning control in potatoes.

Controlled browning is often required in different food processing

operations to promote desirable sensorial attributes in the finished products. The

coloured intensity for the specific product development is regulated by the amount

of enzymes and its respective substrate. The processing quality of prunes, black

raisins, figs, tea, cocoa and coffee is largely dependent on the presence of their

indigenous polyphenol oxidase activity (Walker, 1995).

2.7 PER OXIDASES (POD)

Peroxidases are also related to the browning of fruits and vegetables

primarily mediated through the break down of hydrogen per oxides (H2O2)

(Loaiza-Velade and Saltveit, 2001). They along with catalase cause the formation

of free radicals and oxygen however unlike catalases they are of different types and

require specific substrate (R) for their activity.

2H2O2 → 2H2O +O2 (Catalase)

H2O2+ RH2 → 2H2O+ O2 (Peroxidase)

Peroxidase catalyses different metabolic functions like auxin catabolism,

bridge formation between cell components, alcohol oxidation and cause the

formation of different metabolites like lignin and suberin (Lejaa et al., 2003).

Nevertheless peroxidase and polyphenol oxidase are the major enzymes

responsible for quality loss in horticultural produce due to phenolic dilapidation

(Francois and Espin, 2001). The liberation of free radicals in response to their

23

enzymatic activity reacts with unsaturated fatty acids and cause the formation of

membrane lipid peroxidation in intra cellular organelles eventually leads to the

cellular desiccation, electrolyte leakage and cellular mortality (Scandalios, 1993).

POD activity increases in fruits and vegetables under stress conditions and

with the progression in their physiological stages i.e ripening, senescence etc

(Aydin and Kadioglu, 2001). El-hilali et al. (2003) reported increase in peroxidase

activities under storage condition in mandarin and the same have been reported by

Setha et al. (2000) in papaya. Anthon and Barrett, (2002) studied the thermal

stability of different enzymes in potatoes at temperature ranges between 60-85oC.

He declared peroxidase being most resistant one followed by pectin methyl

esterase, polyphenol oxidase, and lipoxygenase. This makes peroxidase the

selective enzyme in fruits and vegetables post harvest studies being thermal stable

and omni present in plant parts. The inactivation of peroxidase provides reasonable

assumption of natural safety that the other quality related enzymes have also been

inactivated. Hence peroxidase activity has also been commonly employed as an

indicator of appropriate blanching in freezing industry.

2.8 PACKAGING SYSTEMS

Fruits and Vegetables are high moisture commodities and thus require

appropriate post ha8rvest techniques to prolong their storage life. Use of suitable

packaging systems extends the storage life by protecting the perishables during

transit, slowing down the ripening process during post harvest storage and

conferring value addition during marketing (Kittur, 1998). The primary advantage

of packaging is that the stored product maintains its novelty and eating quality as

24

compared to those stored in air. The stored commodities can fetch premium price

in the market only if the quality and quantity of the competing product is poor. The

efficient marketing tactic can recuperate the supplementary packaging costs with

rational profit (Maria, 2007).

Packaging is a vital component of post harvest supply chain management in

horticultural crops. In Pakistan and other developing countries large jute bags

(mostly expired cereal bags) with carrying capacity of 80-100 kg are being utilized

for potato packaging. The present uses of such poor quality second hand bags are

responsible for the disease indicence followed by the bulk of commodity loss

during transportation and storage. In this regard no systematic effort has yet been

carried out to study the response of indigenous potato crop to the type and

permeability of different packaging materials. The quality oriented packaging

system like polyethylene, polypropylene, polystyrene, bio degradable plastics,

corrugated cartons, cushioning materials are required in compliance with food

safety standards to compete the international market for valuable foreign exhange.

Fruits packed in modified atmosphere packaging decrease the consumption

of respiration substrates i.e organic acids and sugars thus preventing the quality of

produce (Ding et al., 2002). Low oxygen and high carbondioxide levels decreases

rate of respiration, restricts ethylene production, curb enzymatic reactions,

minimize physiological disorders and eventually conserve the eminence of the

perishables. Browning disorders and tissue senescence can efficiently be inhibited

by decreasing oxygen and increasing carbon dioxide in the storage atmospheres

(Robert et al., 2003) in addition elevated carbon dioxide also reduces the effect of

ethylene especially in climacteric fruits (Mathooko et al., 1995).

25

The influence of MAP on horticultural commodities varies with gaseous

exhange, storage period, variety and packaging permeability (Rakotonirainy et al.,

2001). Reduced oxygen (<2%) in storage atmosphere however effects

tricarboxylic acid cycle (TCA) as a consequence of anaerobic respiration.

Unoxidized pyruvic acid accumulation resulted into ethanol formation with

subsequent off flavor development and tissue disintegration (Kays, 1991).

Therefore changes in oxygen and carbon dioxide levels should be under significant

threshold level (Beaudry et al., 1999). This can be achieved by establishment of

suitable packaging system with appropriate permeability to avoid anerobiosis

during the post harvest storage.

Transition in the quality attributes of horticultural commodities under

different packaging systems have been an important point of interests for the

researchers. Potato storage under controlled atmosphere is not recommended due to

the increased rate of respiration under high carbon dioxide level (Fonseca et al.,

2002). On the other hand extremly low oxygen level leads to the onset of anaerobic

respiration followed by tissue breakdown and off flavor development (Kays, 1991).

Packaging has been considered as best alternate for potato storage by employing

modified atmospheric condition around the stored tubers. The prevention of off

flavor development due to the efficient packaging also proved to be advantageous to

get superior quality processed products.

Different types of packaging systems have been employed to minimize post

harvest losses in potato. Rosenfeld et al. (1995) employed different types of

packagings like polyester, mesh, colored paper and polyethylene bag for “Beate”

potato variety under 5°C and 23°C temperature for 1 and 2 weeks storage. The

26

highest Glycoalkaloid contents at elevated temperature were observed in all

packaging systems. Blue colored polyethylene attained maximum while black

colored polyethylene maintained minimum glycoalkaloid contents. Gosselin and

Mondy, (1989) packed Russet Burbank and Cheftain potato varieties in paper and

polyethylene bags and evaluated their physico-chemical parameters at an interval of

1, 4 and 8 weeks. He reported that the potatoes packed in polyethylene were lower in

weight loss and ascorbic acid and showed higher polyphenols and glycoalkaloids

contents than those packed in paper during the storage at 20 oC. Similar information

was reported by Abong et al. (2011) who found significant difference in the

ascorbic acid contents in four Kenyan potato varieties during post harvest storage.

He found significant reduction in ascorbic acid contents in potato strips during

harvest, packaging, storage and processing. Shetty et al. (1999) layed the

guidelines for the prevention of soft rot, dry rot and silver scurf diseases in freshly

packed potato. Careful harvest, gentle handling, sorting, washing, drying and

packaging at temperature 45-50 oF should be carried out to avoid disease

proliferation during storage and transportation.

Oner and Walker, (2011) investigated the effect of modified almosphere

packaging on the quality attributes of refrigerated potato strip prior to processing.

He concluded that two step blanching (60 and 98oC) of potato strips followed by

aseptic packaging increased the storage life of potato strips with appreciable post

processing attributes. Baskaran et al. (2007) demonstrated improved quality

attributes in minimally processed potato cubes stored under modified atmosphere

packaging in conjunction with low dose gamma irradiation. Beltran et al. (2005)

studied different sanitizers like water; sodium hypochlorite, sodium sulfite,

27

ozone Tsunami, and the combination of ozone–Tsunami were evaluated on

microbiological and sensorial characteristics of fresh cut potato in modified

atmosphere packaging. The combination of Ozone-Tsunami under modified

atmosphere packaging has been found the most capable treatment against

microbial load.

Packaging systems decreases weight loss and increase ascorbic acid in

tomato (Sammi and Masud, 2007, Badshah et al., 1997) however under prolong

storage duration low ascorbic acid contents have also been reported (Batu and

Thompson, 1998). The application of calcium chloride and potassium

permanganate along with packaging materials has been reported to increase the

storage life in tomatoes (Saammi and Masud, 2007) and apricots (Ishaq et al.,

2009). Alsadon et al. (2004) studied tomato packaging at three different

temperature regimes i.e. 5°C, 15°C and 25 °C and 97% relative humidity.

Maximum storage life was observed at 5°C while higher fungal decay and fast

color development were reported at 25°C. Improved post harvest storage life was

also observed in peach cultivars (O Henry’ and ‘Elegant Lady’) under modified

atmosphere packaging (Zoffoli et al., 1997). Similar observations were recorded

for packed peaches cultivar i.e. Yumyeong at 0 ◦C for 4 weeks storage with higher

electrical conductivity than the control (Choi and Koo, 1997). Das et al. (2006)

studied the effect of MAP and controlled atmosphere (CA) on the accurance of

Salmonella Enteritidis in cherry tomatoes. He found increased mortality rate of S.

Enteritidis on tomato surface that were stored in MAP than those placed in

Controlled atmosphere and air. He concluded that modified atmosphere packaging

is effective in preventing microbial and insect contamination

28

Different packaging systems are commonly supplemented with low

temperature storage (Kyriacou et al., 2009), sprout inhibitors/suppressants (Frazier

et al., 2004), ethylene scavengers (Abbasi et al., 2004), edible coatings (Khuyen et

al., 2008), irradiation (Blessington et al., 2007) etc. in formulating an integrated

strategy to minimize post harvest losses. In addition these packaging materials are

processed into sheets, wraps, pouches and containers by employing different

processing operations providing barrier properties during physiological gaseous

exchange (Hong et al., 2003). Modified atmosphere packaging (MAP) has been

found effective in quality persistence of horticultural commodities under post

harvest storage (Beaudry, 1999) and found inexpensive as compare to Controlled

atmosphere storage (Tuil, 2000). It is employed in the storage of fruits and

vegetables by using plastic films which restrict the exchange of respiratory gases,

primarily increases carbon dioxide and decreases oxygen around the produce

eventually prolonged the storage life (Sanchez et al., 2003). In general packagings

can be employed around fresh fruits and vegetables in two different confirmations.

Firstly to establish a modified atmosphere passively by employing packaging

material of suitable permeability and secondly to create modified atmosphere

actively by flushing out the air from the packaging material with specified gas

mixture. The purpose is to maintain an optimum level of gases inside the

packaging causing a decrease in respiration with out being detrimental to the

product quality (Durand, 2006).

Different types of packaging materials with specific permeability have been

employed for horticultural produce. The plastic packaging had better effect against

weight loss, retards hardening and had similar impact on quality parameters as

29

edible coatings. The combined effect of plastic packaging along with different

edible coating can be effective in storage stability of horticultural commodities.

Polyethylene packaging has been extensively used for providing modified

atmosphere around fruits and vegetables. They are of different types like High

Density Polyethylene Pcakaging (HDPE), Medium Density Polyethylene

Packaging (MDPE) and Low Density Polyethylene Packaging (LDPE). The use of

proper type depends on the type of produce and storage conditions. HDPE has high

tensile strength and low cost but limits gaseous exchange however the use of

LDPE is preferred for their application in tomatoes (Alsadon et al., 2004) owing to

its improved gaseous exchange, better flexibility and good clarity (IQS, 2005).

Polypropylene based bag and bio based polymeric matrix were used to pack the

cherry fruits and investigations revealed that oriented polypropylene based bag

displayed best results under normal atmospheric conditions (Conte et al., 2009).

The modification in different packaging materials has been reported especially in

the produce having high rate of respiration. This is carried out by introducing pores

of defined size and number in the packaging material (Exama et al., 1993). The

packaging modification can also be achieved by amalgamation of ethylene & vinyl

acetate oriented polypropylene and low density polyethylene, which resulted in

achieving excellent results for storing the produce over a long period of time. The

incorporation of sorbic anhydride in polyethylene packaging film along with its

antimycotic potential has also been demonstrated by Weng and Chen, (1997).

The use of synthetic packaging being of petroleum origin and non-

biodegradable nature pose many ecological problems. So efforts should be carried

out to convert or replace plastic packaging into biodegrable and environmental

30

friendly packaging. The organic raw materials like starch, cellulose, proteins,

chitin/chitosan can be used as better alternative. The use of Chitosan application

was found useful in lowering respiration rate, reduced polyphenol oxidase activity,

delayed colour change, decreased weight loss and inhibition of the post harvest

decay in longan fruit (Jiang and Li, 2001). Another pattern of using biodegradable

packaging is the cross linking of natural polymers with synthetic monomers.

Nevertheless due to rapid industrial growth and food security issues practically it

seems impossible to completely replace the synthetic plastics.

2.9 POTATO GREENING

Formation of chlorophyll in cortical parenchyma due to light exposure

results in undesirable greening process (Pavlista, 2001) and is also associated

with public health concerns due to the formation of toxic glycoalkaloids and

economic loss during marketing. Unlike glycoalkaloids, chlorophyll is non

toxic however greened potatoes are of poor economic value and considered

unfit for human consumption (Percival, 1999). Light and mechanical damage

are the most imperative post harvest factors affecting the synthesis of

glycoalkaloids in potato tubers (Plhak and Sporns, 1992).

The phenomenon of potato greening is usually avoided by the farmers in

Pakistan during early morning harvest there by preventing them from exposure to

direct sunlight as also suggested by Woolfe, (1987). The harvest is usually

followed by on farm storage in pits by the farmers or in dark cold storage by the

processor. However exposure of potato tuber to light during post harvest

handling and marketing is inevitable specifically during their retail display in

31

super stores under intensive illuminations. Comprehensive study of tubers

response to different colored light along with the transition in their quality

attributes is required to identify the best illumination for indigenous premium

potato variety for retail display storage where ever required in the local and

export market.

Potato stored under different light types showed variable physiological

responses. The effect of indirect sunlight, fluorescent light, storage in darkness

under room temperature and storage in darkness under refrigerated conditions

was investigated for 14 days on the total glycoalkaloid content of potato tubers

(Rita et al., 2007). Highest chlorophyll and glycoalkaloids contents were

reported in the fluorescent light with steady increase through out their storage

period. Irrespective of light and temperature source small sized tubers attained

higher chlorophyll and glycoalkaloids concentrations. Edward and Cobb,

(1996) investigated that the potato tuber exposure to direct sunlight in field

and fluorescent light in super market increases the chlorophyll and

glycoalkaloids production. Tuber exposure to sunlight, fluorescent,

ultraviolet, and luminous lights after harvest, during storage, transit and

marketing causes chlorophyll and glycoalkaloids accumulation thus poses

main concerns to producer, processor and consumer (Percival, 1994). The

influence of light sources on different potato varieties during storage has been

investigated by Sengul et al. (2004). Potato tubers from Marfona and Granola

varieties were separated as normal, greened, wounded and sprouted. Potatoes

storage was carried out in normal store dark, normal store light, retail

32

refrigerator dark and retail refrigerator light. They observed that high

temperature; light, physical damages and post harvest handling were

significant factors responsible for the accumulation of glycoalkaloids

concentrations ranged between 0.66-32.76 mg/kg f.w in different tubers. The

response of different potato varieties (Kerrs Pink, King Edward and Desiree)

under different light source (low pressure mercury, high pressure mercury,

high pressure sodium and Fluorescent warm white) has been reported by

Percival et al. (1993). He concluded that glycoalkaloid and chlorophyll

contents were found maximum in King Edward and higher glycoalkaloid and

chlorophyll contents were recorded in sodium and fluorescent lights as

compare to those placed under low and high pressure mercury lights.

The influence of light duration on the potato tubers have also been

reported by Zrust et al. (2001). He found two fold increase in glycoalkaloid

contents in potato varieties under light exposure for 14 days (68.6 mg kg-1)

than those placed for 7 days (33.1 mg kg-1). The simultaneous increase in

chlorophyll and glycoalkaloids contents under prolong exposure to light

sources has also been reported (Griffiths et al., 1994).

The effect of different temperatures (5, 10, 20 and 25°C) on chlorophyll

and glycoalkaloids accretion in potato cv. King Edward under low photon density

has been studied by Edwards and Cobb, (1997). The maximum chlorophyll

contents were indentified at 20 °C while the concentration of glycoalkaloids

remained unaffected under different temperature regime.

33

2.10 POTATO GLYCOALKALOIDS

Glycoalkaloids (GA) are predominantly found in different species of

family solanaceae i.e potatoes (Solanum spp.), tomatoes ( Lycopersicon

spp.), egg plant (aubergines spp.) etc. however some of them are also

present in non solanaceous plants like apple, sugar beet, cherries

etc.(Friedman, 2006). They are the naturally occurring toxic compounds in

potato reported to have anti microbial, anti fungal and insecticidal properties

contributing to the immune response of the crop against different diseases,

pests, insects, and animals (Rodriguez-Saona et al., 1999). GA are present in

different parts of potato plant like flowers, young leaves, tubers, eyes, peels

and sprouts however, its maximum amount is present in the tuber peripheral

layer and periderm cell parenchyma (Friedman et al., 2003).

Total glycoalkaloid are present in the forms of α-solanine (C45 H73 NO15,

Mol wt. = 868.07) and α-chaconine (C45 H73 NO14, Mol. Wt = 852.07) contributing at

least 95% of the total in potato. Both of them are structurally alike, holding a same

aglycone (solanidine), Carbohydrate moiety in α-solanine is composed of glucose,

galactose and rhamnose (β-solatriose), while in α-chaconine is of glucose,

rhamnose and rhamnose (β-chacotriose) (Nema et al., 2008). Cholesterol has

been considered as the precursor of GA synthesis in potato which is present as

the major sterol present in the potato. Biosynthesis of Solanidine is believed to be

associated with cholesterol which causes the formation of α-solanine and α-

chaconine by galactosylation or glucosylation respectively (Smith et al., 1996). The

ratio of concentration of α-solanine and α-chaconine depends on the variety,

anatomical plant parts, agronomic practices and ranges 1:2 to 1:7 (Bejarano,

34

2000). The development of GA is related with the potato greening, however no

metabolic link has been identified between chlorophyll and GA biosynthesis

(Edward and Cobb, 1997).

The quantity of glycoalkaloids in food is attributed to its medicinal or

toxicological properties. Low quantities (below 15mg/100g f.w) impart

flavor and functional value, while high quantities (above 20 mg/100g f.w)

can impart bitter taste and even may even cause death at excessive intake (28

mg/100g f.w) (Mensinga et al., 2005). Joint WHO/FAO expert committee on

Food additives (JECFA, 1993) established 10mg/100g fw of GA intake as of

no adverse effect level however; the upper safe limit for their intake is

suggested at 20mg/100g f.w (Papathanasiou et al., 1999). This upper safe

limit has been established for acute toxicity and does not correspond to

possible chronic disorders therefore the upper limit recommended at 5-7

mg/100g TGA in potato cultivars suitable for human consumption (Valkonen

et al., 1996).

The primary effects of GA toxicity in human metabolism appear in

the gastrointestinal tract characterized by diarrhea, vomiting, and abdominal

pain (Patel et al., 2002). The secondary toxicological effects of GA are

associated with different neurological disorders like paralysis,

bronchospasm, cardiac failure, dizziness, headache etc. GA affects the

nervous system firstly by the disruption of membranous phospholipids and

secondly by the inhibition of acetyl cholinesterase activity, an enzyme

responsible for acetylcholine regulation, a compound required for nerve

impulses conduction (Mensinga et al., 2005). The intake of GA in human

35

diet under permissible limits has also been associated with some beneficial

effects. They are reported to posses anti allergic, anti inflammatory (Choi

and koops, 2005), anti cancer (Lee et al., 2004), anti asthma (Dorland, 1994)

and cholesterol lowering effects (Friedman, 2006).

The formation of GA in potato during pre and post harvest period is

dependent on several factors like cultivars, environment, harvesting

conditions (temperature and time), physiological stages (maturity,

sprouting), phytopathogens, mechanical injuries (bruising, wounding), Light

(intensity, duration, wavelength), packaging (color, type, permeability) etc.

(Nema et al., 2008). The proper management of all these factors can keep

the formation of this toxin under permissible limit. GA in the potato tubers

are not destroyed during boiling, baking and frying however, they are

reduced during different processing operations (peeling, cutting, dicing etc)

involved in the production of value added products like chips, French fries

(Peksa et al., 2006).

2.11 LOW TEMPERATURE SWEETENING

Improper storage of vegetables is very critical in under developed

countries due to poor transportation and high temperature that favors decay rather

than storage. Natural physiological processes (ripening, respiration, evapo-

transpiration), physical damages, microbial invasion limits the storage life of the

fresh produce. These all factors are directly or indirectly influenced by different

temperature variables. Temperature is most important factor in determining the

post harvest quality and life under storage (Bachmann and Earles, 2000). Low

36

temperature slows down the enzymatic activities, hinder respiration rate, retard

softening and determine the final nutritional composition (Madhavi and

Salunkhe, 1998). Keeping horticultural commodities under low temperature

storage is therefore a very efficient technique to reduce the post harvest losses;

however its optimum range for specific produce is very much critical to avoid

various disorders like, Chilling injury, freeze injury, and the most important

being potato specific low temperature sweetening etc.

Potato storage under low temperature is employed to extend the post

harvest storage period by extending the natural dormancy through an imposed

dormancy (Wiltshire and Cobb, 1996). Generally in commercial storage, after

curing (stimulation of suberization and wound healing) tubers are purposely

stored at 3-5°C for seed, at 6-9°C for fresh market and at 10-15°C for processing

(Western Potato Council, 2003) however, their storage temperature is largely

related with the undesirable hexose accumulation termed as low temperature

sweetening (Tamaki et al., 2003).

Low temperature sweetening in potato tubers starts with in few days and

is characterized by the degradation of starch polymers into sucrose due to

inactivation of glycolytic enzymes (Phosphofructokinase and fructose-6-

phosphate phosphotransferase). Sucrose is further hydrolyzed into glucose and

fructose by the activity of enzyme invertases (Sonnewald, 2001). Reducing

sugars accumulation in potato tubers during low temperature storage is of prime

industrial concern due to its participation as substrate in maillard reaction at

elevated temperature. The high level of reducing sugars gives rise to

commercially unacceptable brown crisp color (Blenkinsop et al., 2002). Kumar et

37

al. (2004) reported that the brown chip color in the potato tubers can be reversed

to some extent by reconditioning them at warmer storage temperature (> 15oC)

before frying. At intermediate temperature sugars are converted back into starch,

or metabolized as respiratory substrate. However the process of reconditioning is

cultivar dependent and does not alleviate the sugars at acceptable level especially

in case of senescent sweetening and considered to be irreversible (Knowles et al.,

2009).

In order to maintain desirable processing quality in selected potato variety

proper temperature management is very important under prolonged storage. The

optimum storage temperature for the premium potato variety “Lady Rosetta”

grown under indigenous conditions is required as the foremost investigation for

the potato growers in the country. Changes in different vital attributes

(especially sugar metabolism) in the premium potato variety under

comparative temperature regimes are of great concern for the processor to

develop export quality product.

2.12 SUGAR

The level of sugars in potato tuber is an important quality attribute with

special reference to post processing browning. The amount of total sugar contents

ranges between trace amounts to 5 % of dry matter (Kyriacou et al., 2009). These

are primarily present in the form of non reducing sucrose and reducing fructose

and glucose (Blenkinsop et al., 2002). Though the role of sucrose in browning is

limited however it serves as precursor for the assembly of reducing sugars

mediated through storage activated enzymes i.e invertases (Kumar et al., 2004).

38

Reducing sugars are present in the form of Aldoses carrying aldehyde functional

group i.e. glucose or in the form of ketoses carrying ketone as functional group

i.e. fructose (Fennema, 1996). The processing quality of potato tuber is however

associated with the presence of reducing sugars being considered as an index of

proper frying color. Non-enzymatic browning during maillard reaction in

processed potato products is associated with the production of neurotoxin acryl

amides (Dewilde, 2006) which is of grave food safety concern.

Different pre harvest factors have been reported to effect the sugar

accumulation in potato during storage like genotype (Gaur et al., 1999), Soil

moisture (Eldredge et al ., 1996), soil nutrients ( Kolbe et al., 1995) temperature

during growth (Pavlista and Ojala, 1997) tuber maturity ( Hertog et al., 1997),

and mechanical stress (Hironaka et al., 2001).

Edwards et al. (2002) reported storage temperature being the major post

harvest factor influencing potato sugar profile. He found minimum sucrose,

fructose and glucose contents at 10 oC storage as compare to those placed at

3.3oC and 8.3oC temperature regimes and also found decline in sugar contents in

potato upon reconditioning. Other post harvest factors may include tuber

dormancy (Fauconnier et al., 2002), senescent sweetening (Wiltshire and Cobb,

1996) and storage temperature (Zhou and Solomos, 1998).

Different assays have been developed to estimate the different sugar

fractions in potato tubers like Lane and Eynon titration method (AOAC, 1990),

colorimetric method (Nourian et al., 2002), high performance liquid

39

chromatography (Rodriguez-Saona and Wrolstad, 1997) and glucose reagent

strips (Martin and Ames, 2001).

2.13 POTATO SPROUTING

Sprouting during the post harvest storage results in extensive economic

losses due to increased weight loss and reduced tuber quality. Sprouting reduces air

flow through the piles under storage thus elevates the average temperature

consequently increases the chances of disease attack and reduced storage life.

Since low temperature storage (4-15°C) is carried out for potato hence sprouting is

also known to be associated with the swift conversion of starch into sugars which

confer substantial commercial loss to the commodity (Sonnewald, 2001).

Sprouting in potato tubers can be prevented either by prying with dormancy

breaking processes using different sprout inhibitors like CIPC, IPC etc. or

restricting the development of meristems by using different sprout suppressants

like essential oils, hot water treatment etc.

Chloro isopropyl N- phenyl carbamate (CIPC) or chloropropham is one of the

most widely used sprout inhibitor for potato which inhibits sprouting by interfering

with mitotic cell division. It disrupts the spindle formation and eternally damages

the meristems (Kleinkopf et al., 2003). It has been applied in storage atmosphere

as thermal fog, spray, dust etc. (Frazier et al., 2004) however its application

should remain under the acceptable EPA (Environmental Protection Agency)

residual level (> 50 ppm). Chloropropham is occasionally used as a mixture with

propham (isopropyl N-phenylcarbamate or IPC) which has the faster but similar

sort of action as CIPC and assumed to achieve better sprout control (Meredith

40

1995a). CIPC application as single dose can attain long-term sprout inhibition, and

often being applied before natural dormancy release in potato tubers under storage

(Frazier et al., 2004). CIPC application is however associated with growing health

concerns related to their potential adverse impacts on human health, as it may

potentially damage erythrocytes, kidney, liver and spleen (Nakagawa et al., 2004)

in addition it has also been related to the ozone depletion (Kerstholt et al., 1997).

The increasing health and environmental concerns have reduced the permissible

residue limits from 50 to 30 ppm in United States on fresh potatoes (Kleinkopf et

al., 2003) and need has raised for safer alternative.

Maleic Hydrazide (MH) is applied as pre harvest sprout inhibitor in potato

crop after the tuber cell division is completed and is translocated from stems and

leaves to the developing tubers (Wiltshire and Cobb, 1996). It is an isomer of

nitrogenous base uracil and believed to interfere with the mitotic cell division.

Tecnazene (1, 2, 4, 5-tetrachloro-3-nitrobenzene) is another volatile sprout

suppressant which is applied as a powder during the potato storage. It appears to

prevent mitotic cell division however the efficacy may be reduced after tubers have

broken dormancy (Meredith, 1995b).

Essential oils and their major components are increasingly being used as

Potato Sprout Suppressants. The environment and food safety concerns regarding

the use of different sprout inhibitors have created need for safer alternatives

primarily as the essential oils extracted through natural sources (Oosterhaven et

al., 1995). Volatile oils have been employed since long in most of the parts of

world for the sprout inhibition in potato. The potatoes were known to bury in pits

covered with leaves of muna (Minthostachys glabrescens) and soil in the Latin

41

American countries like Argentina, Peru etc. for sprout inhibition (Vaughn and

Spencer, 1993). These volatile oils are less noxious imparting peculiar odor of

their parent source (Buchanan et al., 2000) served as defense mechanism against

microbial and insect loads (Rajendran and Sriranjini 2008) and also being used in

aromatherapy, colognes, and cooking spices (Vaughn and Spencer, 1991).

Vokou et al. (1993) reported that different aromatic plants like spearmint

(Mentha spicata L), penny royal (Mentha pulegium L), rosemary (Rosmarinus

oficinalis L.) and sage (Salvia fruticosa L) rich in essential oils like carvone,

pulegone, and 1,8-cineole were found effective against potato sprout inhibition. He

further added that the application of essential oils only interfere with the growth

and elongation of emerging sprouts thus precisely be called as sprout suppressant

rather sprout inhibitors. Oosterhaven, (1995) identified oil extracts from aromatic

plants like pepper mint (Mintha piperita), caraway (Carum carvi L.) and dill

(Anethum graveolens L.) as potent sprout suppressant for potato. Aromatic plants

like, Japanese mint (Mentha arvensis L., rich menthol contents), lemongrass

(Cymbopogon flexuosus L., high in citral) (Farooqi et al., 2001) and basil

(Ocimum americanum L., elevated linalool contents) (Singh et al., 1997) were

also reported to carry suppressing effects against potato sprouting during storage.

In addition to their sprout suppressing effect essential oils also been reported to

carry significant fungicidal (Gorris et al., 1994), bactericidal (Vokou et al., 1993)

and insecticidal (Isman, 2006) characteristics thus prolonged the post harvest

storage life of potato.

Essential oils are the secondary metabolites primarily present as terpenoids

and phenylpropanoids produced inside the epidermal and mesophyll tissues of

42

plant in the special morphological modifications like secretory glands, resin ducts

etc. The principal components present in the essential oils belong to the class of

chemical compounds called terpenoids which are produced from different

precursors like Isopentenyl pyrophosphate (IPP) and Dimethylallyl

pyrophosphate (DMAPP) during several metabolic pathways (Sangwan et al.,

2001). These are present either as mono terpenes, sesqui terpenes, di terpenes, tri

terpene and tetra terpene produced during pyruvate and mevalonate pathways

(Buchanan et al., 2000). Essential oil composition inside the plant depends on

developmental stages, agronomic practices, and post harvest procedures (Hay,

1993). Carvone is an important member of mono terpene family a prominent

constituent of spearmint, caravay, dill weed is an important compound for potato

sprout inhibition. Carvone biosynthesis in spearmint starts with the combination

of IPP and DMAPP to form geranyl diphosphate (GPP). Initially GPP is cyclized

to limonene which in turn hydroxylated to trans-carveol, which is eventually

oxidized to carvone (Bouwmeester et al., 1998). Phenylpropanoids are less

frequent in essential oils and act as natural defense mechanism against

microorganism, insects and animals (Sangwan et al., 2001). Phenyl alanine and

tyrosine are the main precursors which cause their biosynthesis during shikimate

pathway (Buchanan et al., 2000). The major phenyl propanoids found in certain

plant essential oils include eugenol, myristicin and methyl cinnamate (Sangwan et

al., 2001). Eugenol is the active component in clove oil being used for potato

sprout suppression. Phenylalanine along with NADPH cause the biosynthesis of

eugenol in the aromatic plants catalyzed through the enzyme eugenol synthase

(Koeduka et al., 2006).

43

In addition different other techniques have been employed to

prevent potato sprouting under storage. Rezaee et al. (2011) exposed potato

tuber cv. Agria with gamma irradiation on different dates during their post

harvest storage. He observed complete sprout inhibition by 50 Gy (Grays)

and 150 Gy at 8oC and 16oC temperature respectively. Saraiva et al. (2011)

reported sprout inhibition in potato tubers by pressure treatment of 100

Mpa for 5-10 min. Low pressure (30-50 Mpa) did not prevented potato

sprouting however found efficient in delaying sprout development.

Kyriacou et al. (2008) investigated impact of different time and

temperature variables regarding hot water treatments for sprout prevention

in potato. He concluded that short duration hot water treatment can prevent

potato sprouting and dehydration during subsequent storage. Rangana et al.

(1998) recommended hot water treatment at 57.5°C for 30 min to improve

storage stability in potatoes. Potatoes storage can successfully be carried

out at 8 or 18°C for 12 weeks without sprouting with no adverse effects on

the over all quality parameters. Shabana et al. (1987) studied the effectiveness

of different wax applications for sprout suppression and found reduced solanine

contents in treated potato during storage.

With the advent of safe food concept and environmental concerns

pertaining to the use of chemical sprout inhibitors like CIPC, IPC, MH the

need arised to develop integrated sprout management approach to ensure

potato storage with out the use of hazardous chemicals. The storage of

premium potato variety with the help of cheap sprout suppresents of natural

origin will facilitate the poor farmers for economic storage. In addition

44

development of potato crop free of such detrimental effect will also enable the

local farmers for “organic” potato storage which recieve top notch in the

international market

2.14 CHIP COATINGS

Potato chips are the oil rich (35-40%) products (Moreira et al., 1999) and

considered as preferred snack food world over due to its palatable taste and ease of

preparation. The high fat contents however of grave concern for the peoples

suffering from chronic heart diseases and obesity. Different techniques have been

employed to minimize the oil contents in the final products like, modification in

size and thickness (Gamble and Rice, 1988), pre drying (Pedreschi and Moyano,

2005), modification in frying techniques (Mehta and Swinburn, 2001) and frying

medium (Berry et al., 1999), frying temperature (Mellema, 2003) and potato chips

coatings (Williams and Mittal, 1999).

Application of different coating materials reduces oil uptake and improves

consumer preference for the fried products. The fat uptake in the fried products is

determined by two mechanisms i.e condensation effect and capillary effect

(Mellama, 2003) which are altered by the application of different coating materials.

Since the fat uptake by the chips is largely the function of its surface properties

thus coating is considered as promising route for its mitigation in finished

processed product. In addition, pre processing coating application on potato

products reported to mitigate likely acrylamide formation in the processed products

(Fiselier et al., 2004). Different types of coating materials are employed during

frying operations however the selections of proper coating material with desirable

45

barrier and mechanical properties are essential for the premium quality production.

These coating materials can be thin and invisible (Gennadios et al., 1997) or thick

like batter (Fiselier et al., 2004).

Albert and Mittal, (2002) studied the effect of different coating materials

like gelatin, gellan gum, methyl cellulose, pectin, sodium caseinate, soya protein

isolates, wheat protein, and found general reduction in fat uptake as compare to

control. Mallikarjunan et al. (1997) reported that the coating with cellular

derivatives cause the formation of protective layer on the surface eventually

decreases the fat uptake in the fried products. Garcia et al. (2002) evaluated the

surface application of cellulose derivatives in different formulations for the

reduction in oil uptake in fried products. He concluded that coating reduced the oil

uptake by 35-40% with appreciable retention of different sensorial attributes.

Garmakhany et al. (2008) studied the comparative effect of different hydrocolloids

(carboxy methyl cellulose, xanthan gum, guar gum) applications on the quality

attributes of potato chips. He revealed that CMC 1% application cause minimum

fat uptake and maximum color scores in the fried products.

Aloevera is tropical and subtropical plant widely known to its theraptic and

medicinal properties (Eshun and He, 2004). It is mucilage gel extracted from leaf

parenchymatic cell predominantly being used since long against cardio vascular

diseases, ulcer, gastro intestinal and renal disorders (Ni et al., 2004). Owing to its

antibiotic and anti inflammatory properties it has also been considered as remedy

against lethal diseases like AIDS and cancer (Renoylds and Dweck, 1999). The use

of aloevera gel has also been increasing in cosmetic industry (Aburjai and Natsheh,

2003) and known to carry antifungal activity (Saks and Burkai-Golan, 1995). In

46

addition it is increasingly being used as functional ingredient in food industries for

ice creams, beverages and desserts production (Moore et al., 1995). It is reported to

carry specific barrier properties and thus used as postharvest edible coating to

increase the shelf life of Cherries (Martinez-Romero et al., 2006) and table grapes

(Valverde et al., 2005).

Selection of aloe vera gel for chips coating in the present study has been

carried out as novel technique in processing. The application was required for the

development of plant based coating material i.e. HALAL (permissible food in

Islamic jurisprudence) to get reduced fat uptake in potato chips along with

appreciable retention of sensorial attributes. Such high quality processed product

would equally be the appreciated by the processor and consumer due to added

economic and health benfits.

2.15 ACRYLAMIDE

Toxic compounds found in thermally processed starchy foods are called as

Acrylamide (AA) (Svensson et al., 2003) and the International Agency for

Research on Cancer declared them to be animal carcinogen (Group 2A), possible

genotoxic carcinogen and neurotoxin to humans (IARC, 1994). The deep fried

starch rich foods like French fries, doughnuts, potato chips and extruded snacks are

rich source of these toxic compounds (Moreira et al., 1999).The presence of this

lethal compound in baked and fried starchy foods has created great concerns

regarding consumer`s food safety.

47

United States is the one of the biggest consumers of potato chips with an

over all consumption of around 1.2 billion pounds per year (USDA 2002).

Previously this consumption of potato chips was not considered as a health hazard,

however a recent study revealed that when starchy foods are subjected to high

temperature during a cooking a process of baking and frying, they release highly

toxic chemicals known as acrylamide, which become a part of the finished product

and present a serious threat to human well being (Kita et al., 2004). Desirable

commercial attributes of aroma, taste and appearance can only be achieved by the

process of browning, which results in caramelization and maillard-reactions

imparting the toxic AA in the finished product.

Several scientists proposed different techniques to mitigate acrylamide

formation in foods during processing. The critical test will however be to attain

significant acrylamide reduction in processed food with intact product sensorial

and nutritional attributes. The concentration of reducing sugars has been the prime

contributor of acrylamide formation during processing and determines the color of

fried products. Potato intended for roasting, frying or baking should contain less

than 1g/kg reducing sugar to mitigate likely acrylamide formation (Biedermann-

Brem et al., 2003). The use of different organic acids has been found very effective

in decreasing the acrylamide contents in the processed products. Low pH plays an

important role in reducing acrylamide formation and primarily being achieved in

different foods through organic acids like citric, acetic and lactic acid (Mestdagh et

al. 2007). Granda et al. (2004) reduced acrylamide formation in potato chips by

vacuum frying between 118oC and 140oC at 1333 Pa. The process minimized

acrylamide formation by 94% without conferring significant modifications in

48

sensorial parameters of processed potato. The use of different hydrocolloids

application during processing confers moisture barrier properties to the food

products. Fiselier et al. (2004) coated potato croquettes with blend of breadcrumbs

and egg before heating and found considerable reduction in acrylamide content

(280 to 50 parts per billion). Vattem and Shetty, (2003) also observed reduced

acrylamide formation (930 to 580 parts per billion) by coating the potato strips

with chickpea batter before deep-fat frying. Large variation in acrylamide contents

has been reported in different potato varieties used in processing operations In

general varieties having low reducing sugar and protein contents have been

associated with reduced acrylamide contents in finished products. Varieties like

Agria, Lady Rosetta, Lady Clair, Lady Jo, Jupitor, Saturna etc. grown under sandy

loam and clay soils are reported to produce less acrylamide contents in French fries

(De Wilde et al., 2006).

The available information on acrylamide formation so far emphasizes

common recommendation on healthy food intake. People should consume

balanced and antioxidants rich diet composed of fruit and vegetables as their major

food segment, and restrains the intake of thermally processed foods. There is

consensus on the health risk caused by the acrylamide hence it can easily be

concluded that if it is not possible to avoid these harmful compounds than there

level should be kept to as low as possible and a term used for the reduced

acrylamide is ALARA (as low as reasonably achievable), which is a globally

accepted principle when it comes to the formation of acrylamide in the food items.

49

Chapter 3

MATERIALS AND METHODS

3.1 PHASE-I

In the 1st Phase physico-chemical, functional and processing attributes of

ten commercial potatoes (Solanum tuberosum L.) were studied. These varieties

were harvested from Potato Research Institute, Sahiwal (Punjab-Pakistan) in

January 2009 and were immediately transferred to the Food Technology

Department, PMAS-Arid Agriculture University, Rawalpindi (Punjab-Pakistan)

where the trials were carried out. Six were yellow-white skinned namely, Agria

(AGR), Atlantic (ATL), Chipsona (CHI), Desi (DES), Hermes (HER) and Satellite

(SAT), four were reddish skinned Cardinal (CRD), Courage (COU), Desiree

(DESR) and Lady Rosetta (LR). These were chosen because of the recent increase

in their production and contribution to the processing industry in Pakistan. The

tubers were graded into homogenous lots of > 50 mm length, sorted for the

exclusion of damaged, diseased and sunburned tubers afterward placed between

15-20oC for suberization for one week.

3.2 PHASE-II

For the 2nd Phase of the study potato variety “Lady Rosetta” was harvested

from Potato Research Institute, Sahiwal (Punjab, Pakistan) in January, 2010. The

experimental material was shifted to the Post harvest Technology Laboratory of the

same University. Potatoes were washed, sorted and graded into homogenous lot

before subjecting to the different analytical trials. The selected tubers were cured

49

50

for one week at temperature between 15-20oC. The second phase is further divided

in to four experiments as described below:

3.2.1 Packaging Trial

Packaging trial of potato variety “Lady Rosetta” was carried out as a 1st

experiment of second phase of the study. Potatoes were packed in different

packaging materials of same size (30 cm × 40 cm) and perforations (10%)

procured from Ms. Multi packages Ltd. (Lahore, Pakistan). The set of treatments

included:

1. T1 = Control

2. T2 = Jute packaging (JP)

3. T3 = Nylon packaging (NP)

4. T4 = Poly propylene packaging (PPP)

5. T5 = Cotton packaging (CP)

6. T6 = Low Density Polyethylene packaging (LDPEP)

7. T7 = Medium Density Polyethylene Packaging (MDPEP)

8. T8 = High Density Polyethylene Packaging (HDPEP).

One Kg potato tubers were placed in each replication and 3 kg tubers were

maintained in each treatment for per day analysis. In total 30 Kg (Thirty packaging

per treatment) potatoes were placed in each treatment later subjected to different

physico-chemical and processing analysis at week and bi week intervals

respectively. All the packaged potatoes were stored at temperature and relative

humidity maintained around 25±2oC and 70±5%, respectively.

51

3.2.2 Light Trial

Light trail of potato variety Lady Rosetta was carried out as 2nd experiment

of the second phase of the study. The potatoes were placed under different light

sources in specially designed cabinets. The trial was divided into following set of

treatments:

1. T1 = Blue light (BL)

2. T2 = Fluorescent light (FL)

3. T3 = Green light (GL)

4. T4 = Mercury Light (ML)

5. T5 = Red light (RL)

6. T6 = Dark (D)

Potatoes were placed under lamp of 20 W of different light sources

maintained at a distance of 1 m during storage except in T6. All the tubers were

bared to specific light and rotated at 24 hours interval to ensure maximum skin

exposure. 1 kg potato tubers were placed in each replication and 3 kg tubers were

maintained in each treatment for per day analysis. In total 30 Kg potatoes were left

in each treatment and were subsequently subjected to different physico-chemical

and processing analysis at three days and a week interval respectively. All the

potatoes were stored at temperature and relative humidity maintained around

25±2oC and 70±5% respectively.

3.2.3 Temperature Trial

Potato variety Lady Rosetta was placed under different temperature

regimes with relative humidity maintained at 70±5% to conduct 3rd experiment of

52

second phase of the study. The potatoes were placed under three temperature

regimes:

1. T1 = 5 ±1oC

2. T2 = 15 ±1oC

3. T3 = 25 ±1oC.

One kg potato tubers were placed in each replication and 3 kg tubers were

maintained in each treatment for per day analysis. In total 30 Kg potatoes placed in

each treatment and were subjected to different physico-chemical and processing

analysis at bi week intervals.

3.2.4 Sprouting Trial

Potato variety Lady Rosetta was subjected to different sprout controls to

conduct 4rth experiment of second phase of the study. Potatoes were subjected to

different treatments as under:

1. T1 = Control

2. T2 = Hot Water Treatment (55 ±2oC for 30 minutes)

3. T3 = Spearmint Oil (1%)

4. T4 = Clove Oil (1%)

5. T5 = CIPC (100 ppm)

Hot water treatment was carried out in water bath maintained at specific

temperature and time once before the start of storage. Spear mint and Clove oils of

100% purity were supplied by Ms. Shah Traders (Karachi, Pakistan). 1%

emulsions each of spear mint and clove oils were prepared in distilled water with

0.05% Tween 80 used as an emulsifier. Tubers were dipped in emulsion for 20

53

seconds ensuring the entire tuber surface was coated. CIPC was procured from Ms.

United Phosphorus Limited (Gujrat, India) and applied once as thermo aerosol in

the storage chambers at specified concentration (100 ppm).



in each treatment during storage (Temp. 25±2oC, R.H. 70±5%) afterward subjected

to different physico-chemical and processing analysis at nine days interval.

3.3 PHASE-III

For the 3rd phase of the study potato variety “Lady Rosetta” was harvested

from Potato Research Institute, Sahiwal (Punjab, Pakistan) in January 2011. The

experimental material was shifted to the Post harvest Technology Lab. Food

Technology Department, PMAS-Arid Agriculture University, Rawalpindi.

Potatoes were washed, sorted and graded into homogenous lot before subjecting to

the different analytical trials. The selected tubers were cured for one week at

temperature between 15-20oC.

The results identified in the 1st and 2nd phase were evaluated in combination

in third phase to assess different quality attributes along with the eventual post

harvest storage life in potato tubers. The potato variety lady Rosetta was given hot

water treatment (55±2oC for 15 minutes) followed by Clove Oil application (1%).

Tubers were packed in Polypropylene packaging and than stored at 10±1oC

temperature and 70±5% R.H. The potatoes were divided into two homogenous lots

for analysis:

1. T1 = Control

2. T2 = Integrated Treatment

54



in each treatment which were subjected to different physico-chemical and

processing analysis at twenty and thirty days intervals respectively.

3.3.1 Potato Chip Coating

In the third phase of study potato processing was carried out only in the

tuber placed in T2 (integrated treatment). Pre processing potato chip coating was

carried out in different levels of Aloe vera gel followed by subsequent frying at

180-185oC temperature. Aloe vera gel was extracted from freshly harvested aloe

vera leaves and blanched at 70oC for 10 minutes. Aloe vera gel was prepared in

three different formulations each with 1% sorbitol (Sigma-Aldrich, USA) added as

plasticizer along with distilled water as under:

1. T1= Control

2. T2 = Aloe vera (10%)

3. T3 = Aloe vera (20%)

4. T4 = Aloe vera (30%)

The potato chips were dipped in prepared formulations for 5 minutes,

allowed to drip off and dried before frying. The frying was carried out at thirty

days interval in potato stored under intergrated treatment.

Different physico-chemical, functional and processing attributes in potato

tubers during different phases (1, 2 and 3) of the present study were performed

55

according to standard methods described as under. All the results were expressed

on dry weight basis in phase no.1 in order to record appropriate comparison

between the selected varieties.

3.4 PHYSICO-CHEMICAL AND FUNCTIONAL ANALYSIS OF

POTATO

3.4.1 Physical Analysis

3.4.1.1 Size

Potato size in terms of linear dimension (L) was determined by digital (0-

150mm, China) with precision of +0.01 mm.

3.4.1.2 Goemetric mean diameter

Geometric Mean Diameter (Dg) was determined by the multiple of Length

(L), Width (W) and Thickness (T) of potato as described in the equation given

below

Dg = (LWT) 0.333

3.4.1.3 Sphericity

Equation described by Ahmadi et al. (2008) was employed for the

determination of tuber Sphericity as under:

Ф= (Dg/ L) ×100

Where as Dg = Geometric Mean Diameter, L= Length

3.4.1.4 Surface area

Equation reported by Baryeh, (2001) was employed for the estimation of

surface area in potato tubers as under:

56

S = π Dg 2

Where, Dg = Geometric Mean Diameter.

3.4.1.5 Tuber counts

Individual tuber counts (TC) in different varieties were estimated manually

per 25 Kg packaging as:

Tuber counts = (TC)/25 Kg.

3.4.1.6 Firmness

Potato tuber Firmness was determined by fruit Firmness Tester model

(Wagner FT-327) euipped with 11mm plunger. Results quantified were converted

in to Kilopascals (Kpa).

3.4.1.7 Specific gravity

Tuber Specific gravity was measured by the estimation of tuber weight in

air and tuber weight in water. The specific gravity was determined by the

following equation as described by Gould, (1995).

Weight in air Specific Gravity =

Weight in air – Weight in water

3.4.1.8 Total soluble solids

Total Soluble Solid (TSS as oBrix) was estimated in the homogenized

potato tuber in each varietals sample by using a Digital refractometer (Model PAL-

III, ATAGO-Japan) as reported by AOAC (1990) method no. 932.12.

Standardization of Instrument was carried out by using distilled water at 25±1oC

temperature.

57

3.4.1.9 pH

The pH values were recorded by using a pH-meter (Inolab. WTW Series,

Germany) as illustrated in AOAC (1990) method no. 981.12. The instrument was

carefully calibrated with Buffers 4, 7 and 10. The reading was recorded by the

direct insertion of electrode in the homogenized sample taken in the beaker.

3.4.1.10 Sprouting

Sprouting (SPRT) percentages in potato tubers (sprout length > 3mm)

were calculated by the equation described by Ranganna et al. (1998).

No. of eyes sprouted Sprouting (%) = × 100. Total no. of eyes

3.4.1.11 Weight loss

The weight loss (%) in different experiments at specified storage

interval was determined by weighing the samples with digital balance (OHAUS,

Model TS4KD Florham Park, NJ, USA) and reported as percent loss in sample

weight based on its initial weight.

Initial weight - Final weight Weight loss (%) = ×100

Initial weight

3.4.2 Chemical Analysis

3.4.2.1 Dry matter

Dry matter (DM) was determined by Oven Drying method at 102oC till

constant weight is achieved as described in AOAC (1990) method no. 934.06. The

calculations were carried out as under:

58

Weight of Fresh sample - Weight of Dry sample Dry Matter (%) = × 100

Weight of Fresh sample

3.4.2.2 Starch

Starch estimation was carried out by making the tuber sugar free by the

repeated extraction with 80% iso-propanol. Tubers were dried at 70oC and than

starch were hydrolyzed by 60% perchloric acid. The glucose was estimated

spectrophotometerically by using anthrone reagent as described by Kumar et al.

(2005).

3.4.2.3 Protein

Crude protein estimation was carried out by multiplying the total nitrogen

contents with conversion factor 6.25 using the Kjeldhal apparatus as described by

AOAC (1990) method no. 920.10. 5grams of homogenized sample was digested

with the addition of 1 gram copper sulphate, 10 grams potassium sulphate and 30

milliliter sulphuric acid in the digestion flask. The procedure was followed by

continuous heating till color less matter was obtained. Consequential material was

diluted with distilled water followed by distillation in the presence of 10 milliliter

sodium hydroxide (40% solution) in the distillation apparatus. The liberated

ammonia was trapped in 4% boric acid solution containing methyl red as indicator.

Distillate obtained was titrated with sulphuric acid (0.1 N solutions) to attain

golden brown end point.

Nitrogen (%) was estimated by the equation described below:

1.4 (V2-V1) × Dilution factor × Normality of HCl N (%) =

Sample weight

59

Protein (%) was estimated as the multiple of Nitrogen (%) and Conversion factor

(6.25)

3.4.2.3 Fat

Crude fat was determined according to the AOAC (1990) method no.

983.23. Dried 10g sample placed in thimble was extracted with hexane (B.P 40-

60oC) taken as solvent in pre weighed soxhlet flask. The solvent was recovered

after the completion of extraction process and fat containing flask was dried in

Oven till constant weight. The crude fat contents were gravimetrically determined

by the following equation.

Weight of flask+ fat - Weight of empty flask Fat Contents (%) = × 100

Weight of sample

3.4.2.4 Sugar

Lane and Eynon titration method using Fehling’s solution was employed

for the estimation of Reducing sugar (RS), non reducing sugar (NRS) and total

sugars (TS) contents as reported in AOAC (1990) method no. 925.35. Ten grams

sample was diluted with 100 ml warm water, stirred thoroughly to dissolve all

suspended particles subsequently filtered in 250 ml volumetric flask. 100 ml of

prepared solution was transfer in to conical flask along with 10 ml of diluted HCl

and boiled for 5 minutes. The resultant solution was cooled and neutralized with

10% NaOH and made up to volume in 250 ml volumetric flask. The solution was

titrated against Fehling`s solution and reading were recorded as under:

4.95 (Factor) × 250 (Dilution) ×2.5 Total Sugar (%) =

Weight of sample × Titre× 10

60

4.95 (Factor) × 250 (Dilution) Reducing Sugar (%) =

Weight of sample × Titre × 10

Non Reducing Sugar (%) = Total Sugar - Non Reducing Sugar

3.4.2.5 Glucose

Glucose estimation was carried out by Glucose test strips imported from

Snack Food Association, (Arlington Virginia USA). The color change was

correlated with the color chart and the values were expressed in percentage (%).

The tests were conducted in triplicate.

3.4.2.6 Fiber

Crude fiber estimation was carried out according to AOAC (1999) method

no.920.86. 5g dried fat free sample was digested with 1.25% sulphuric acid

followed by 1.25% NaOH solutions. The residue obtained filtered, washed and

ignited in muffle furnace at 550oC till the formation of white ash.

Crude fibre estimation was carried by the following equation:

(c-b) – (d-b) Crude Fibre (%) = × 100

(a) Where; a = Sample weight, b = crucible weight, c= sample weight before ignition

d= sample weight after ignition.

3.4.2.7 Ash contents

Ash content was determined AOAC method no. 940.26 (1990). 5g sample

was directly incinerated in the muffle furnace at 550oC till grayish white residue

was obtained. The ash content was estimated as:

61

Weight of Ashed sample Ash contents (%) = × 100

Weight of sample

3.4.2.8 Mineral composition

Mineral estimation in potato tubers was carried out according to AOAC

(1999) method no. 923-07 with some modifications. Five grams sample was

digested at 180- 200oC temperature in the presence of nitric acid and perchloric

acid in the ratio of 7 milliliters and 3 milliliters respectively to acquire transparent

clear contents. The received transparent contents were diluted with bidistilled

water in 100 ml flask. Mineral contents like iron, magnesium, calcium in potato

tubers were estimated by Atomic Absorption Spectrophotometer (GBC-932

Australlia) against their standard curves of known concentrations. Estimations of

sodium and potassium were determined by Flame Photometer (Model PFP 7

Jenway, England) whereas phosphorus detection was carried out in

Spectrophotometer (CE-2021, 2000 series CECIL Instruments Cambridge,

England).

3.4.3 Functional Assays

3.4.3.1 Ascorbic acid

Ascorbic acid (AA) estimation was carried out by titrametric method by

employing 2, 6, di-chlorophenol indophenol dye (redox dye) as explained in

AOAC (1990) method no. 967.21. 10 g representative sample was taken in beaker

and made up to volume with 100 ml 3% Phosphoric acid and filtered. 10 ml of

filtrate was titrated with the standard dye solution till pink end point. The ascorbic

acid contents were quantified as under:

62

Dye factor × Titration × Volume made up Ascorbic acid (mg/100g) = × 100

Weight of sample × Volume of filtrate

Dye standardization: Five milliliters of standard ascorbic acid solution was diluted

with five milliliter of metaphosphoric acid (3%) and titrated with dye

solution till pink color endures for ten seconds. Dye factor was estimated (mg

ascorbic acid/ ml of dye) as:

Dye Factor (D.F) = 0.5/ titration.

3.4.3.2 Total glycoalkaloids

The Total glycoalkaloids (TGA) determination was carried out by the

method described by Grunenfelder et al. (2006). Ground lyophilized potato tissue

(500 mg) was extracted in 10 ml of 80% ethanol at 85-90oC for 25 minutes. The

extract were filtered and reduced to 3-5ml on rotary evaporator at 50oC. Each

extract was rinsed twice with 3ml of 10% (v/v) Acetic acid and than centrifuged at

10,000g for 30 minutes at 10oC. The pH of the supernatants was adjusted at 9.0

with NH4OH. The extract was refluxed at 70oC for 25 minutes followed by

overnight storage at 4oC temperature. The extract were similarly centrifuged as

earlier, after discarding the supernatants the resulting pellets were dissolved in 0.5

ml of 7%( v/v) phosphoric acid and stored at -20oC. The Total Glycoalkaloids were

estimated by adding 200µL of extract in 1 ml of 0.03% (w/v) in concentrated

phosphoric acid. The contents were allowed to settle for 20 minutes and

absorbance was measured at 600nm. TGA concentrations were quantified based on

63

α-solanine (Sigma-Aldrich) standard curve using a CE-2021, Spectrophotometer

(CECIL Instruments Cambridge, England) and expressed as mg TGA/100g d.w.

3.4.3.3 Chlorophyll

Chlorophyll (CHL) extraction from different tuber samples was carried out

by acetone and subsequent quantification was done in spectrophotometer as

illustrated by Percival, (1999). Five grams representative (selected from each side

of potato tuber) lyophilized tissues were ground to a fine powder with the help of

mortar and pestle. Sample was transferred to test tubes followed by extraction with

10 milliliter of acetone. The extract was vortexed than stored at 4oC for 24-72

hours. After storage chilled extracts were again vortexed and centrifuged for 15

minutes at around 2,500 g. The supernatant was collected for chlorophyll

determination.

Chlorophyll content was measured in 1.00-cm cuvettes at A647 and A664.5

using Spectrophotometer (CE-2021, 2000 series CECIL Instruments Cambridge,

England).

Total chlorophyll concentrations were expressed as mg/100g d.w from the

following equation:

Total Chl = 17.90 (A647) + 8.08 (A664.5)

3.4.3.4 Total phenolic contents

Total phenolic contents (TPC) in terms of Gallic acid Equivalent (GAE)

were carried out by Folin–Ciocalteu (FC) assay as explained by Lachmann et al.

(2008) with few modifications. Tubers randomly selected were freeze dried and

64

than extracted thrice with 80 % ethanol to get representative plant extract. 2 gm

extract was quantitatively converted into 100 ml volumetric flask and adjusted with

80% ethanol. In 5 ml of the sample slightly diluted with distilled water, 2.5 ml of

FC and 7.5 ml of 20% solution of sodium carbonate were added. Contents were

allowed to settle for 2 hours and absorbance was measured at 765 nm using a CE-

2021, Spectrophotometer (CECIL Instruments Cambridge, England). Total

phenolic contents were quantified by standard calibration curve derived from the

absorbance of known Gallic acid concentration (10-100 ppm). Results were

articulated as mg Gallic Acid Equivalents (GAE) per 100g d.w.

3.4.3.5 Radical scavenging activity (RSA)

Antioxidant activity was measured as radical scavenging activity (RSA)

using method described by Singh and Rajini, (2004) that involves electron transfer

reaction based assay by employing free radical 2, 2-diphenyl-1-picrylhydrazyl

(DPPH). Five mg of freez dried potato extract was incubated with 1.5 ml of DPPH

solution (0.1mM in 95% Ethanol). The reaction mixture was properly shaken and

allowed to stand for 20 minutes under ambient temperature. Absorbance of the

resultant mixture was determined at 517nm against blank. The radical scavenging

activity was determined as decrease in the absorbance of DPPH using the

following equation.

Asample 517 nm Scavanging effect (%) = 1 - x 100

AControl 517nm

65

3.4.3.6 Enzyme estimation

3.4.3.6.1Extraction and protein estimation:

Enzyme extraction was carried out by the method described by

Yemenicioglu, (2002) with some modifications. Washed, peeled and diced

potatoes were placed under -20oC before homogenate preparation. 200 grams

frozen potato was homogenized with 300 ml acetone and 1gram

polyvinylpolypyrrolidone (PVPP) in waring blender. The resultant mixture was

homogenized for 2 minutes subsequently filtered through whatman No.1. Acetone

powder preparation was carried out by repeated extraction and evaporation. The

extraction mixture was prepared by mixing 0.4 g PVPP, 2g acetone powder and 50

ml of cold 8.8% Sodium chloride solution. Extraction was completed at 4oC

temperature 3 hours under magnetic stirrer. The extract was filtered, centrifuged at

11000g for 20 minutes and subsequently stored at -20oC prior to enzyme

estimations.

Protein estimation was carried out by Lowry method using bovine serum

albumin (BSA) as standard. Protein standards of crude and partially purified

extracts were prepared in 8.8% NaCl solution and deionized water respectively. All

the assays were carried out in triplicate. The enzyme activity was calculated as

U/g fresh weight, in spectrophotometric assay 1 U was defined as 0.001 change in

absorbance per minute per ml of enzyme extract.

3.4.3.6.2 Polyphenol oxidase (PPO) assay:

Poly phenol Oxidase (PPO) activity was determined by the method as

described by Yemenicioglu, (2002). The reaction mixture contained 2ml 0.01M

66

sodium phosphate buffer (pH 7.0), 0.2 ml of 0.25 M catechol and 0.3 ml enzyme

extract to the total volume of 2.5 ml. The optical density (OD) of the reaction

mixture was determined spectrophotometerically at 420 nm. PPO activity was

calculated by the change in OD over a period of thirty seconds and expressed as

U/g fresh weight.

3.4.3.6.3 Per oxidase (POD) assay:

Peroxidase estimation was carried out as reported by Abbasi et al. (1998).

Reaction mixture consisted of 2.1 ml, 15mM NaKPO4 buffer (pH 6.0), 0.3 ml

1mM H2O2, 0.3 ml 0.1 mM guaiacol and 0.3 ml enzyme extract to the total volume

of 3 ml. The optical Density (O.D) of the reaction mixture was determined

spectrophotometericaly at 470 nm. POD activity was estimated by the change in

O.D due to guaiacol oxidation over thirty seconds time and expressed as U/100g

fresh weight.

3.4.4 Potato Chips Evaluation

The potato tubers during different experiments were processed into potato

chips. Peeled tubers were sliced (1.2-1.5 mm thick) and blanched in 1.5% NaCl

solution at 85oC for 2 minutes. After pre drying the chips were fried in electric

fryer at 180- 185oC temperatures for 3 minutes using palm oil. The fried chip were

cooled and placed in Dry Oven at 105oC till constant weight for moisture contents

(MC) estimation The fat absorption (FAB) in different chip samples were

determined by Soxhlet Extraction apparatus as described by AOAC (1990) method

no. 983.23. The estimation of Glycoalkaloids (TGA) as solanine in potato chips

67

was carried out by the same method as described above. Twenty five students

including the faculty members of Department of Food Technology who were the

habitual consumers of the potato chips selected as judge for the sensory evaluation.

The judges were requested to record their degree of preferences for Crispiness

(CRP), Flavor (FLV) and Taste (TAS) according to the five point hedonic scale as

described by Kita (2002). The Color (COL) of the chips was correlated with

British Potato Council (BPC) Frying color chart and the values were expressed as

approximate L-values.

3.5 STATISTICAL ANALYSIS

Results obtained in first phase of the study were subjected to statistical

analysis by considering the varieties as variation source, using one-way analysis of

variance (ANOVA). Statistical differences with P-values under 0.05 were

considered significant. Date obtained in second and third phases were statistically

analyzed by two factor factorial in Completely Randomized Design (CRD) using

M-StatC Statistical software as described by Steel et al. (1997).

68

Chapter 4

RESULTS AND DISCUSSION

4.1 PHYSICO-CHEMICAL, FUNCTIONAL AND PROCESSING ATTRIBUTES OF POTATO VARIETIES

In the 1st phase of the present study ten commercial potato varieties namely,

Agria, Atlantic, Cardinal, Courage, Chipsona, Desiree, Desi, Hermes, Lady Rosetta

and Satellite were studied for their physical, chemical and functional attributes,

with special reference to their potential in chip processing.

4.1.1 Physical Attributes of Potato Varieties.

Table-1a summarizes the mean values obtained for each of the varietals

physical attributes like, Size, Geometric Mean Diameter (GMD), Sphericity,

Surface Area, Tubercounts/25Kg, Firmness, Specific Gravity, TSS, pH and

Sprouting Potential. The results of one way Anova to compare the means for

different varieties are also included. The significant differences were recorded

between varieties for their physical parameters which were correlated (Table-1b).

Hermes yielded maximum tuber size (94.25 mm) followed by Desi (91.20 mm)

and Desiree (85.41 mm) and were inversely related to the tuber counts/25Kg

packaging (R= -0.967). Hermes exhibited maximum surface area (18010.93 mm2)

followed by Courage (16067.80 mm2) and Lady Rosetta (15924.29 mm2). Variety

Atlantic experienced maximum sphericity (95.38%) followed by Lady Rosetta

(94.29%). The parameters discussed above have essential role in defining the

processing yield of different varieties as described in British Quality Chip Charter

by British Potato Council (BPC). The sugar contents were significantly higher

in small sized tubers (Misra and Chand, 1990) thus the tubers < 50 mm sizes

68

69

Table 1a Physical attributes of potato varieties. Variety Size

(mm)

GMD (mm)

Sphericity (%)

Surface area (mm2)

TC/25 kg Firmness (Kpa)

Specific Gravity

TSS (oBrix)

pH SPRT (%)

AGR 76.27 ± 2.95 d

66.93 ± 1.53 d

87.75 ± 2.57 b

14075.25 ± 9.71 e

160.00 ± 1.12 c

799.00 ± 7.88 g

1.081±0.09 f

5.44 ± 1.18 h

6.17 ± 1.12 e

47.50 ±2.12 g

ATL 64.99 ± 1.73 f

61.99 ± 2.17 e

95.38 ± 2.38 a

12077.79 ± 8.81 g

186.30 ± 0.98 a

925.00 ± 5.19 b

1.092 ± 0.06 b

5.54 ± 1.12 g

6.21 ± 1.16 c

42.33 ±1.36 h

CAR 83.30 ± 2.30 c

66.51 ± 1.15 d

79.84 ± 3.19 d

13903.31 ± 7.03f

155.00 ± 1.15 d

775.00 ± 4.04 h

1.074 ± 0.03 g

5.73 ± 1.17 d

6.15 ± 1.29 f

59.33 ±1.54 c

COU 78.43 ± 3.88 d

71.50 ± 2.28 b

91.16 ± 3.33 ab

16067.80 ± 8.31 b

154.30 ± 0.81 d

885.00 ± 5.48 c

1.090 ± 0.09 bc

5.69 ± 1.11 e

6.27 ± 1.16 a

53.75 ±2.15 e

CHI 68.53 ± 2.96 e

58.81 ± 1.47 f

85.81 ± 1.64 bc

14029.32 ±10.53 ef

166.00 ± 0.77 b

883.00 ± 3.64 c

1.089 ± 0.11 c

5.63 ± 1.36 f

6.17 ± 1.17 e

50.00 ±1.99 f

DESR 85.41 ± 2.37 c

68.31 ± 1.11 c

79.97 ± 2.17 d

14666.04 ± 9.48 d

150.30 ± 0.89 e

760.00 ± 5.19 j

1.070 ± 0.08 h

5.93 ± 1.15 a

6.27 ± 1.36 a

63.00 ±2.45 b

DESI 91.20 ± 4.15 b

70.92 ± 3.57 b

77.76 ± 3.81 de

15808.17 ± 13.72 c

131.00 ± 0.92 f

845.00 ± 8.77 e

1.086 ± 0.07 d

5.88 ± 1.39 b

6.25 ± 1.12 b

90.66 ±3.15 a

HER 94.25 ± 3.57 a

75.70 ± 2.17 a

80.31 ± 2.28 d

18010.93± 11.88 a

125.70 ± 1.20 g

829.00 ± 9.73 f

1.084 ± 0.04 de

5.62 ± 1.19 f

6.13 ± 1.11 g

36.00 ±1.27 i

LR 75.49 ± 2.87 d

71.18 ± 2.23 b

94.29 ± 3.37 a

15924.29 ± 9.43 b

165.70 ± 0.33 b

948.00 ± 6.92 a

1.102 ± 0.02 a

5.55 ± 1.49 g

6.18 ± 1.09 de

46.25 ±1.96 g

SAT 64.67 ± 1.81 f

54.50 ± 2.57 g

84.27 ± 2.47 c

9335.49 ± 3.56 h

185.30 ± 0.88 a

862.00± 4.61 d

1.083 ± 0.09b e

5.83 ± 1.20 c

6.27 ± 1.12 a

56.67 ±1.66 d

Dissimilar letters with in the column indicated significant difference (p< 0.05)

Value ± corresponds to the standard error

AGR (Agria), ATL (Atlantic), CAR (Cardinal), COU (Courage), CHI (Chipsona), DESR (Desiree), DESI (Desi), HER (Hermes), LR ( Lady Rosetta), SAT (Satellite)

GMD (Geometric Mean Diameter), TSS (Total Soluble Solids), SPRT (Sprouting Potential)

70

Table 1b Correlation between physical attributes

Size

GMD

Sphericity

Surface

area TC/25 kg

Firmness

Specific Gravity

TSS

pH SPRT

Size 1

GMD 0.831 1

Sphericity -0.669 -0.146 1

Surface area 0.784 0.925 -0.168 1

TC/25 kg -0.967 -0.804 0.651 -0.836 1

Firmness -0.531 -0.140 0.778 -0.069 0.451 1

Specific gravity -0.363 0.061 0.738 0.138 0.267 0.959 1

TSS 0.074 -0.277 -0.511 -0.092 -0.111 -0.328 -0.434 1

pH -0.187 -0.248 -0.003 -0.374 0.222 0.035 -0.110 0.169 1

SPRT 0.335 0.026 -0.553 -0.027 -0.319 -0.290 -0.283 0.437 0.537 1

71

were eliminated during the frying process. Tubers of Lady Rosetta followed by

Atlantic attained maximum Specific gravity (Table1a) and were significantly

correlated (R=0.979) with their Firmness (Table-1b). Cardinal and Desiree were

amongst the varieties with low specific gravity values. Difference between the

varieties on the basis of their specific gravity has also been reported by previous

researchers (Kumar et al., 2005). The maximum TSS was determined in Desiree

(5.930 oBrix) followed by Desi (5.880 oBrix). A narrow range in the pH values (6.12-

6.65) was observed in different tested varieties with non significant difference was

recorded between Courage, Desiree and Satellite. Varieties like Lady Rosetta and

Chipsona also exhibited non significant difference (P<0.05) in their pH values. The

minimal variations between the pH in different varieties were also accounted by

Gomez et al. (1997). At ambient storage (temp. 25±2 oC & R.H 60 ±5 %) for 60 Days,

Desi showed maximum sprouting percentage (90.66%) followed by Desiree (63.0%)

and Satellite (59.33%), in contrast longer dormancy and minimum sprouting was

experienced in Hermes (36.00%) and Atlantic (42.33%) (Table-1a).

4.1.2 Proximate Analysis of Potato varieties

Expressing proximate composition on dry weight basis (Table 2a) Lady

Rosetta produced the tubers with maximum Dry Matter (25.90%) and Starch contents

(77.39%) while lowest Dry Matter (21.24%) and Starch Contents (72.14%) were

estimated in Desiree. Highly Significant correlation (R= 0.986) was recorded between

these two quality parameters in all tested varieties (Table 2b) which confirmed the

previous findings by Casanas et al. (2002). A close range was estimated in the fat

contents (0.803 % to 1.293%) with maximum observed in Desi and minimum in Lady

72

Table 2a Proximate analysis of potato varieties (d.w basis).

Variety DM % Starch (g/100g)

Protein (g/100g)

Fat (g/100g)

Total Sugar (%)

Reducing Sugar (%)

N. R. S (%)

Fibre (g/100g)

Ash (%)

AGR 22.91 ± 1.22 g

74.42 ± 2.30 e

11.86 ± 1.27 b

0.970 ± 0.012 c

0.810 ± 0.017 h

0.110 ± 0.023 h

0.700 ± 0.012 h

7.24 ± 0.41 d

3.300 ± 0.581 bc

ATL 24.99 ± 2.91 b

76.69 ± 2.67 b

10.89 ± 2.39 d

1.000 ± 0.085 c

1.170 ± 0.058 f

0.320 ± 0.017 fg

0.850 ± 0.023 g

7.44 ± 0.61 c

1.897 ± 0.292 h

CAR 22.35 ± 0.95 h

73.62 ± 2.03 f

11.43 ± 2.07 c

0.970 ± 0.017 c

1.940 ± 0.023 c

0.450 ± 0.058 cd

1.290 ± 0.012 d

7.67 ± 0.40 b

3.250 ± 0.179 c

COU 24.75 ± 2.60 cd

76.52 ± 2.50 b

09.93 ± 2.35 f

0.810 ± 0.012 d

1.380 ± 0.017 e

0.400 ± 0.029 ef

0.980 ± 0.006 e

7.57 ± 0.52 bc

2.820 ± 0.581 f

CHI 24.45 ± 2.95 d

75.71 ± 1.95 c

11.00 ± 2.93 d

1.015 ± 0.011 c

1.385 ± 0.058 e

0.430 ± 0.058 de

0.960 ± 0.029 f

7.71 ± 0.55 b

2.889 ± 0.239 e

DESR 21.24 ± 3.81 I

72.14 ± 2.32 g

13.29 ± 2.91 a

1.275 ± 0.046 a

2.400 ± 0.058 b

0.570 ± 0.040 c

1.820 ± 0.040 a

6.75 ± 0.14 f

3.580 ± 0.115 a

DESI 23.89 ± 1.29 ef

75.45 ± 1.73 d

09.88 ± 1.28 f

1.293 ± 0.030 a

2.590 ± 0.035 a

0.900 ± 0.055 a

1.690 ± 0.058 b

7.83 ± 0.58 a

1.990 ± 0.237 h

HER 23.35 ± 5.87 f

75.36 ± 1.75 d

11.81 ± 2.33 b

0.997 ± 0.013 c

1.555 ± 0.035 d

0.383 ± 0.015 ef

1.170 ± 0.017 e

6.43 ± 0.75 g

3.107 ± 0.292 de

LR 25.90 ± 4.82 a

77.39 ± 1.32 a

10.50 ± 1.20 e

0.803 ± 0.026 d

0.935 ± 0.023 g

0.220 ± 0.012 gh

0.710 ± 0.023h

7.19 ± 0.58 d

2.560 ± 0.351g

SAT 22.82 ± 1.23 g

74.15 ± 1.92 f

11.95 ± 1.39 b

1.252 ± 0.015 b

2.250 ± 0.115 b

0.700 ± 0.029 b

1.550 ± 0.029c

6.94 ± 0.11 e

2.999 ± 0.186 e



d.w: Results expressed on dry weight basis

DM (Dry Matter), NRS (Non Reducing Sugars)

73

Table 2b Correlation between proximate components

DM Starch Protein Fat

Total

Reducing Sugar

N. R. S Fibre

Ash

Total

minerals

DM 1

Starch 0.986 1

Protein -0.803 -0.812 1

Fat -0.620 -0.634 0.421 1

Total sugar -0.589 -0.595 0.220 0.840 1

Reducing sugar -0.312 -0.317 -0.070 0.797 0.935 1

N.R.S -0.676 -0.680 0.365 0.863 0.983 0.875 1

Fibre 0.376 0.314 -0.695 -0.152 -0.030 0.150 -0.172 1

Ash -0.714 -0.717 0.748 0.031 0.067 -0.212 0.179 -0.488 1

Total mineral -0.472 -0.448 0.538 -0.199 -0.106 -0.338 -0.011 -0.528 0.898 1

74

Table 3 Mineral composition of potato varieties.

Variety Na (mg/ 100g)

K (mg/ 100g)

Fe (mg/ 100g)

Ca (mg/ 100g)

P (mg/ 100g)

Mg (mg/ 100g)

Total minerals (mg/ 100g)

AGR 6.83 ±0.15h 466.00 ±9.66b 1.760 ±0.12d 18.03 ±2.8a 63.83 ±2.61b 21.00 ±1.86g 577.50 ±16.20 a

ATL 9.55 ±0.29a 347.30 ±7.66i 2.277 ±0.19a 16.58±1.45c 40.67 ±2.14i 25.00±1.57cd 441.36±12.30 h

CAR 7.37 ±0.15f 460.10±6.45c 1.680±0.10ef 17.75±1.44ab 55.17±3.20e 27.67 ±1.72a 569.75±12.06 c

COU 7.42 ±0.15f 437.80 ±5.15e 1.823 ±0.18c 14.32 ±1.30d 51.43 ±4.56f 24.85±1.16 d 537.64±11.64 e

CHI 8.33 ± 0.14e 382.00 ±4.73h 2.143 ±0.27b 12.80 ±0.58g 42.33 ± 2.41h 27.73 ±1.12a 475.30±15.13 g

DESR 7.15 ±0.29g 482.00±8.07a 2.193 ±0.36b 13.20 ±0.98f 45.67 ±3.14g 24.30±1.06 e 574.55±13.92 b

DESI 8.55 ±0.29d 434.10 ±11.18f 1.450 ±0.12g 13.63 ±1.69e 57.00 ±2.57d 26.00 ±1.28b 540.73±9.25 e

HER 8.73 ±0.21c 453.50 ±7.85d 1.627 ±0.15f 17.45 ±1.73b 62.00 ±3.57c 25.53±1.06 c 568.80±13.57 c

LR 9.27 ±0.15b 426.00 ±11.52g 1.843 ±0.18c 16.90 ±1.45 c 71.33 ±5.14a 23.47 ±2.14f 548.85±18.58 d

SAT 6.69 ±0.55h 451.90 ±7.66d 1.707±0.29de 12.70 ±1.15g 36.17 ±1.14j 18.47 ±1.14h 527.62±10.93 f



Na (Sodium), K (Potassium), Fe (Iron), Ca (Calcium), P (Phosphorus), Mg (Magnesium).

75

Rosetta. Proximate analysis revealed that mean protein contents in potato varieties

were significantly different as also been mentioned by Casanas et al. (2009). Desiree

attained maximum Protein contents (13.29 %) while Desi was amongst the variety

with minimum (9.88%). Evaluation of total Sugar of potato varieties indicated that

Agria attained the least Sugar contents (0.810 %) followed by Lady Rosetta (0.935 %).

Reducing sugars and protein contents in the tuber varieties at elevated temperature

caused the formation of neurotoxin i.e acrylamide and thus of grave food safety

concern. The formation of this carcinogen (Tareke et al., 2002) in potato chips during

processing is directly linked with the maillard reaction (Mottram et al., 2002).

Therefore the right selection of potatoes for processing with respect to low

reducing sugar contents would be an important mitigation strategy against the

formation of this lethal compound.

Table-2a revealed the amount of nonstarch polysaccharides (as fibres) present

in different potato varieties. Desi produced maximum fibre contents ((7.830%)

followed by Chipsona (7.717%) and Cardinal (7.670%) with minimum recorded in

Hermes (6.430%). The ash Contents in the tubers were well differentiated and ranged

from 3.580 % in Desiree to 1.897% in Atlantic, and are highly correlated (R=0.898)

with their total mineral contents (Table-2b). Agria (577.5 mg/100g) and Desiree

(574.5 mg/100g) were preferred over all other varieties for their mineral composition,

followed by Cardinal (569.7 mg/100g) and Hermes (568.8 mg/100g) (Table-3),

however individual mineral dominance exhibited slight deviation from the general

trend.

76

4.1.3 Functional Attributes of Potato Varieties

Table-4a expressed the results on dry matter basis pertaining to the functional

characteristics of different potato varieties which are of the major food safety concerns

with positive correlation recorded in most of them. A close range of ascorbic acid

contents (78.50 mg/100g – 115.0 mg/100g) with non significant difference (P<0.05)

were recorded in the some of varieties, however maximum ascorbic acid contents were

recorded in Desi followed by Hermes and Desiree. Radical Scavenging Activity in

different potato varieties were significantly correlated (Table-4a) with other functional

parameters like Ascorbic acid (R= 0.802), Total Glycoalkaloids (R= 0.856) and Total

phenolic Contents (R=0.953). These results partly coincide with the findings of

Hejtmankova, et al., (2009). The maximum Glycoalkaloids which were estimated as

α-solanine were observed in Desi (22.35 mg/100g) followed by Hermes (19.66

mg/100g). Satellite accumulated maximum Chlorophyll contents (1.397 mg/100g)

followed by Agria and Desi (Table-4a) Glycolkaloids have been considered as one of

the toxins related to the human diet with upper safe limit of 20mg/100g on Fresh

Weight basis (Papathanasiou et al., 1999). However it is also believed to be a natural

defense mechanism in plants against some pathogens and insects (Rodriguez-Saona et

al., 1999). In all the tested varieties the amount of Glycoalkaloids were found lower

than the permissible limit considered safe for human intake. The significant

correlation between the Glycolkaloids and other functional components (Table-4b) in

selected potato varieties might be attributed to their anti malignant properties (Lee et

al., 2004). Amongst all Desi followed by Desiree and Agria attained maximum total

77

Table 4a Functional attributes of potato varieties (d.w basis).

Variety AA

(mg/100g)

TGA

(mg/100g)

CHL

(mg/100g)

TPC

(mgGAE/100g)

RSA

(%)

AGR 94.40 ±2.23 c 17.29±2.17 c 1.374±0.295 a 189.11± 8.66 c 59.92 ±0.73 b

ATL 80.50 ±1.15 f 15.34±2.02 d 1.037±0.236 cd 129.17± 9.82 g 38.95 ±0.17 g

CAR 82.00 ±2.05 ef 12.25±4.05 f 0.895±0.875 e 115.35±10.00 i 35.50 ±0.17 i

COU 83.00 ±1.55 e 14.17± 3.08 e 1.274±0.176 b 93.58± 5.77 j 37.54 ±0.17 h

CHI 76.45 ±1.15 h 11.40 ±4.05 g 1.013±0.231 d 125.74± 8.86 h 42.87 ±0.29 f

DESR 109.19 ±3.47 b 19.66±3.19 b 0.811±0.290 f 192.98± 6.06 b 59.29 ±0.15 b

DESI 115.00 ±4.66 a 22.23±2.20 a 1.292±0.115 b 253.24± 7.32 a 68.12 ±0.64 a

HER 110.00 ±3.88 b 19.24±4.06 b 1.089±0.522 c 150.33±10.55 e 52.50 ±0.58 d

LR 87.71 ±2.73 d 17.25±5.03 c 0.904±0.237 de 171.55± 6.32 d 56.90 ±0.16 c

SAT 78.29 ±2.30 g 12.55±3.11 f 1.397±0.583 a 132.96 ±13.01 f 44.74 ±0.81e

Dissimilar letters with in the column indicated significant difference (p< 0.05), Value ± corresponds to the standard error, d.w: Results expressed on dry weight basis.

AA (Ascorbic Acid), TGA (Total Glycoalkaloids), CHL (Chlorophyll), TPC (Total Phenolic Contents), RSA (Radical Scavenging Activity)

Table 4b Correlation between functional attributes

AA

TGA

CHL

TPC

RSA

AA 1 TGA 0.893 1 CHL -0.023 -0.001 1 TPC 0.784 0.845 0.102 1 RSA 0.802 0.856 0.129 0.953 1

78

phenolic contents and radical scavenging activity (Table-4a) with significant

correlation (R=0.953) between them (Table 4b). The results expressed were in close

confirmation with the finding of Lachmann et al. (2008).

4.1.4 Potato Chips Evaluation

Table-5a expressed post processing quality parameters like moisture contents,

fat absorption and sensory evaluation in different potato varieties. Mean moisture

contents (%) ranges between maximum (1.697%) in Desiree to the minimum (1.203%)

in Lady Rosetta. Maximum fat absorption (40.61%) was recorded in Desiree and

minimum (27.48%) in Atlantic. In general the fat absorption (%) in chips were

inversely proportional to the Dry matter contents as low fat absorption were recorded

in varieties like Atlantic, Lady Rosetta, Hermes, Agria, Courage, Chipsona etc. The

results were in close agreement with the findings of Kita, (2002). Different steps in

chip processing like peeling, cutting, slicing, washing and frying caused considerable

reduction (82.00% in Lady Rosetta – 76.73% in Desi) in glycoalkaloids in all the

tested varieties, which has also been reported by Peksa et al. (2006).

In general highly positive correlation was observed between all the sensory

attributes recorded by the judges (Table-5b). The response of judges regarding the

chip color was correlated with British Potato Council (BPC) chip chart to calculate the

approximate L-values. The best Chip color was displayed by Lady Rosetta (L-64.80)

followed by Agria (L-63.80)>Atlantic (L-63.20)>Hermes (L-63.10)>Courage (L-

63.0). The paramount color scores in Lady Rosetta is attributed to its low sugar and

protein contents thus also confirmed the findings of Kyriacou et al. (2008).

79

Table 5a Evaluation of potato chips

Variety CMC (%)

FAB (%)

TGA (mg/100g)

COL (L-value)

CRP Scores

FLV Scores

TAS Scores

AGR 1.289 ±0.21 e 30.67 ±3.15g 3.80 ± 0.34c 63.80 ± 1.32b 4.25 ±0.58de 4.10 ±0.57de 4.35 ±0.33cd

ATL 1.315 ±0.19de 27.48 ±2.30h 2.80 ±0.41e 63.20 ±1.84c 4.30 ±0.44cd 4.12 ±0.60d 4.33 ±0.10d

CAR 1.463 ±0.33c 37.45±2.71b 2.60 ±0.19f 61.08 ±2.81g 3.80 ±0.67 g 4.03 ±0.33e 4.06 ±0.33e

COU 1.327 ±0.44d 32.15 ±1.17f 2.87 ±0.18e 63.00 ±1.50d 4.20 ±0.58e 4.21 ±0.44c 4.00 ±0.23e

CHI 1.303 ±0.32e 32.95±2.92ef 2.48 ±0.15g 62.85 ±1.86de 4.25 ±0.60de 4.21 ±0.44c 4.39 ±0.47c

DESR 1.697 ±0.39a 40.61 ±5.71a 3.99±0.29b 60.40 ±2.87h 3.65 ±0.59h 3.10 ±0.58g 3.10 ±0.58h

DESI 1.513 ±0.11b 35.97 ±1.88c 5.20 ±0.26a 62.50 ±1.99e 4.00±0.74f 4.03 ±0.33e 3.50 ±0.58 g

HER 1.240±0.22 f 30.15±2.94g 4.04 ±0.30b 63.10 ±1.71cd 4.45 ±0.62b 4.36 ±0.19b 4.50 ±0.57b

LR 1.203 ±0.19g 27.77±1.80h 3.15 ±0.24d 64.80 ±0.91a 4.75 ±0.28a 4.85 ±0.12a 4.80 ±0.19a

SAT 1.467 ±0.45c 34.19 ±1.66d 2.46 ±0.21g 61.85 ±0.88f 4.00 ±0.33f 3.56 ±0.33f 3.86 ±0.88f



CMC (Chip Moisture Contents), FAB (Fat Absorption), TGA (Total Glycoalkaloids), COL (Color), CRP (Crispiness), FLV (Flavor), TAS (Taste)

80

Table 5b Correlation between potato chips attributes

MC

FAB

TGA

COL

CRP

FLV

TAS

MC 1

FAB 0.911 1

TGA 0.272 0.218 1

COL -0.893 -0.902 -0.003 1

CRP -0.921 -0.920 -0.101 0.947 1

FLV -0.894 -0.775 -0.099 0.863 0.880 1

TAS -0.959 -0.864 -0.394 0.812 0.877 0.867 1

81

Crispiness is an important quality feature in chip, mostly characterized by high Dry

matter and Starch contents. Potatoes with high specific gravity possessed

substantial starch contents along with higher molecular weight non starch

polysaccharides thus imparting stable, compact and thin configuration as also

mentioned by Kita, 2002. Lady Rosetta secured maximum crispiness scores (4.75)

followed by Hermes (4.45) > Atlantic (4.30) > Agria (4.25) > Chipsona (4.25).

Almost the same trend followed in the taste and flavor scores recorded by the panel

of judges (Table-5a) Lady Rosetta maintained it supremacy over all other varieties

with maximum flavor (4.85) and taste (4.80) Scores followed by Hermes.

4.2 EFFECT OF DIFFERENT PACKAGING MATERIALS ON THE

QUALITY ATTRIBUTES OF POTATO

As first experiment of 2nd phase of study the efficiency of different

packaging materials like jute, nylon, polypropylene, cotton, low density

polyethylene, medium density polyethylene and high density polyethylene were

studied along with control on the premium potato variety “Lady Rosetta” (selected

in the first phase). Physico-chemical and functional assays of potato tubers and

processing performance of potato chips were evaluated at an interval of seven and

fourteen days respectively.

4.2.1 Effect on Weight Loss (%)

The general trend was an increase in weight loss (%) in all the treatment;

however the rate of weight loss was slower in packaged potato as compare to

control during the storage period. Treatment means of packaged potato showed

non significant difference between T2 and T8, T4 and T6 while all other differed

significantly. Data on weight loss revealed significant differences between all the

82

storage means. The interaction between treatment means and storage intervals

showed maximum weight loss (%) in T1 and minimum in T6 at the end of storage

(Fig. 1).

Maximum weight loss was recorded in control (T1) while poly propylene

packaging (T4) showed minimum weight loss till the end of nine week storage at

ambient temperature. In general potato packed in different polyethylene

packagings (T6, T7, T8) showed lesser weight loss as compare to jute, nylon and

cotton packagings i.e T2, T3 and T5 respectively. Amongst all the treatments weight

loss during different storage intervals showed slow initial increase (0.89 to 1.252

%) till fourth week which subsequently progressively ascended up to 6.619 and

10.90 % in T1 and T4 respectively till the end of 63rd day (Fig 1). This slow initial

increase in weight loss presented non significant interaction between storage

intervals and treatments during early week’s storage which became significant

after sixth week till the end of storage.

The loss of water activates the series of complex metabolic activities thus

considered as an important stability index for the storage life assessment in fruits

and vegetables. The weight loss in potato is attributed to the water loss through

peel tissues due to physiological processes like respiration and sprouting (Tester et

al., 2005). Different post harvest management techniques are employed in order to

increase the storage stability of horticultural commodities like modified

atmosphere packaging, controlled atmosphere packaging, coatings, irradiation etc

(Abbasi et al., 2004). Controlled atmosphere storage has not been considered

suitable for potato storage due to its high rate of respiration under elevated carbon

dioxide level (Fonseca, 2002).

83

0

2

4

6

8

10

12

1 7 14 21 28 35 42 49 56 63

Storage intervals (day)

Wei

ght

loss

(%

)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 1 Weight loss in potato under different packagings showing minimum loss in polypropylene and LDPE during storage

(LSD (0.05) for treatment = 0.0509 LSD (0.05) for interval = 0.0570 LSD (0.05) for interaction = 0.1613)

Vertical bars show ±SE of means.

84

Different modified atmosphere packaging has been evolved as an inexpensive and

most appropriate alternate (Tuil, 2000) to reduce gaseous exchange and water loss

during storage. Packaging systems confer barrier properties to the physiological

gaseous exchange and resulted in eventual decreased weight loss under storage

period (Hong et al., 2003).

Minimum weight loss during the present study in packaged potato was

primarily due to high moisture level and restricted gaseous exchange maintained

inside as compare to control. The permeability and type of different packaging

materials however showed significant difference in their physiological weight

losses during the storage. In potato packed in polyethylene packaging ( T6, T7, T8)

the weight loss increases with the increase in the thickness as increased weight loss

has been observed in high density polyethylene packaging as compare to those

packed in low density polyethylene. The similar information regarding thickness

and permeability of packaging material has been reported by Rakotonirainy et al.,

(2001). The application of polyethylene packagings in different horticultural

products like potato (Rosenfeld et al., 1995), tomato (Sammi and Masud, 2007),

mango (Abbasi et al., 2011) apricot (Ibrahim, 2005), loquat (Chen et al., 2003) etc.

have been found effective in decreasing weight loss during their post harvest

storage. Conte et al. (2009) reported best storage stability under polypropylene

based packaging in cherries. Similar results regarding efficacy of polypropylene

packaging during post harvest storage has been reported by Calderon et al. (2008).

Minimum weight loss in potato stored in low density polyethylene packaging (T6)

and polypropylene packaging (T4) as compare to other packaging materials and

control confirmed the finding of the researchers reported above.

85

4.2.2 Effect on Total Soluble Solids

Data pertaining to the total soluble solid (TSS) in potato exhibited general

increase during the storage period. The increase in TSS was more pronounced in

T1 as compare to all other treatments. Treatment means indicated minimum

retention of TSS in T4, followed by T2, T3 and T6 with non significant difference

recorded between them. Storage interval means showed significant difference in

TSS except during the first and second weeks and maximum retention was

observed in case of ninth week storage. In general non significant interaction

between treatment means and storage intervals means became significant after

the third week storage (Fig. 2).

TSS accumulation in all the packaging materials was steady during the

early weeks which progressively increased with the increase in storage duration.

Maximum retention of TSS value estimated in control (6.34obrix) and HDPE (6.26

obrix) packaging, while minimum accumulation observed in jute (6.07obrix) and

polypropylene (6.11obrix) packagings at the end of ninth week storage. TSS values

remained statistically similar amongst all other packaging at the end of storage

period. Overall different packagings retained lower TSS accumulation as compare

to control.

Total soluble solids in fruits and vegetable primarily correspond to the

presence of soluble sugars, salts, acids etc. however the change in TSS is

predominantly related with sugar metabolism during the post harvest storage.

86

5.50

5.70

5.90

6.10

6.30

6.50

1 7 14 21 28 35 42 49 56 63


Tot

al s

olu

ble

sol

ids

(oB

rix)

Control

Jute

nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 2 Total soluble solids in potato under different packagings showing highest increase in control during storage



87

Changes in TSS are directly related with the hydrolytic conversion of

insoluble starch polymers into soluble sugars during the post harvest period (Kittur

et al., 2001). In general conversion of starch into sugar is an important index of

ripening in most of the climacteric fruits. Physiological conversion of starch into

sugars in potato is slower as compare to other fruits and vegetable and is

specifically undesirable due to the eventual loss of color in processed products

(Tamaki et al., 2003).

Different packaging materials are known to reduce water loss and starch

hydrolysis due to lower respiration rate inside storage atmosphere consequently

retained lower TSS accumulation as compare to control. Increased TSS

accumulation in control might be due to concentration effect because of increased

water loss with subsequent soluble solute accumulation in cell vacuoles. These

results were in line with the findings of Munoz et al (2006) who reported low TSS

accumulation under controlled rate of respiration. Several other researchers also

reported that modified atmosphere packaging resulted in controlled conversion of

starch into sugars in tomato (Sammi and Masud, 2007), guava (pervez et al.,

1992), oranges (Attia, 1995) which are in line with the findings of present

investigations.

4.2.3 Effect on pH

Data related to pH in potato exhibited decrease with the increase in storage

period however the rate of decrease in pH was faster in T1 as compare to all other

treatments. Treatment means showed maximum pH retention in T4 followed by T7

and T6, while minimum pH was recorded in T1 and T3 while T5 and T8 were found

statistically similar. Significant statistical difference was recorded in all the Storage

88

5.7

5.8

5.9

6

6.1

6.2

1 7 14 21 28 35 42 49 56 63


pH

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 3 pH in potato under different packagings showing maximum retention in polypropylene and LDPE during storage



89

interval means. Storage interval means progressively decreased from first week till

the ninth week storage. The interaction between treatment means and storage

intervals revealed significant difference at α = 0.05 (Fig. 3).

Minimum retention of pH value found in Control (5.76) followed by

cotton packaging (5.79) at the end of 63rd day storage. Highest pH value

estimated in potato packed in MDPE packaging (5.97) followed by polypropylene

packaging (5.96). Potato packed in LDPE and Jute packagings also retained

appreciable pH value at the end of storage time. The pH decline in jute packaged

potato remained steady through out the storage period and maintained reserved

value by the end of storage.

Considerable decline in pH observed in control by the start of 4rth week i.e

6.10 to 6.04 while the same happened to most of other treatments by the start of

sixth week. Potato packaged in different polyethylene packaging, polypropylene

packaging and cotton packaging revealed the onset of decline in pH by the start of

third week. In terms of relative change the decline in pH by ninth week storage

observed in polypropylene and MDPE packaging was similar to that quantified in

control on seventh week. The considerable response of stored potato to different

packaging systems revealed their efficacy in post harvest management of this

valuable crop

pH measures the available hydrogen ion concentration and carries anti

microbial characteristics in the pulp of fruits and vegetable and their slight change

cause considerable change in electrolyte concentrations (Olsson et al., 2004).

Reduction in pH value was observed in all the samples which entails that the

potato tubers turned more acidic with the increase in storage period. In general

90

packagings retained higher pH value than the control due to the better retention of

total acids which inturn increasd the hydrogen ion concentration. The variation in

pH value with in different packagings might be due to their type and permeability

in holding these organic acids during storage. Similar observations have been

recorded by Babarinde and Fabunmi (2009) regarding better retention of pH in

LDPE packaged vegetables than in control. In addition pH retention during storage

as result of improved packagings like polypropylene, LDPE maintained the

horticultural commodities more resistant to decay and microbial attack thus

improved the storage stability which was also observed in the present

investigations. The decline in pH during storage alone or in response to different

packaging systems has also been reported by different researchers in potato

(Nourian et al., 2003), mango (Manzano et al., 1997) and tomato (Sirinivasa et al.,

2006). Some researchers have reported decrease in pH of potato slices intend for

processing may cause low acrylamide formation in final products (Jung et al.,

2003). This is however achieved by intentional soaking of potato slices in different

organic acid solutions prior to frying (Pedreschi et al., 2004).

4.2.4 Effect on Specific Gravity

The general trend was an initial increase in specific gravity in potato

followed by a gradual decline till the end of storage. The rate of decline in specific

gravity value was higher in T1 as compared to other treatments. Treatment means

revealed non significant difference in most of the treatments except control.

Storage Interval means remained statistically same at early and mid storage period

however differed significantly at the end. In general except in T1 interaction

between treatments and storage intervals was also found non significant (Fig. 4).

91

1.095

1.1

1.105

1.11

1.115

1 7 14 21 28 35 42 49 56 63


Sp

ecif

ic G

ravi

ty

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 4 Specific gravity in potato under different packagings showing maximum value in LDPE during storage (LSD (0.05) for treatment = 0.001613 LSD (0.05) for interval = 0.001800 LSD (0.05) for interaction = 0.005099)


92

Specific gravity value progressively increased with the storage period by

the fourth week and than gradually decreased till the end of storage period. Potato

packed in polypropylene packaging (T4), LDPE packaging (T6), MDPE packaging

(T7) and HDPE packaging (T8) retained maximum value during fourth, fifth, and

sixth week storage. T6 retained maximum specific gravity value (1.106) in contrast

to control (1.100) by the end of ninth week. Over all results revealed that different

packaging systems had statistically no significant effect on the specific gravity

value up to ninth week storage.

Specific gravity is largely associated with the total dry matter content in

potato as promising co relation (R= 0.93) has been reported by Kumar et al.

(2005). The observed changes in specific gravity can be associated with the

changes in their dry matter contents which are primarily referred to the starch

contents present in potato.

In all treatments during initial weeks slight increase in specific gravity

value had been observed as freshly cured potatoes favored the formation of dry

matter (Kaul et al., 2010). Rivero et al. (2003) reported that post harvest storage of

potato at ambient temperature is characterized by concurrent processes like

transpiration and starch degradation resulted in simultaneous increase and decrease

in dry matter contents respectively. In the present study starch losses are

compensated by water loss due to evapo-transpiration causing over all negligible

change in specific gravity as happened during most of storage period. In later

stages of storage the rate of starch degradation exceeds the rate of water loss in

different treatments in general and in control in particular causing significant

decrease in specific gravity. Hydrolysis of starch is accelerated by the sprouting in

93

all potato except in those packed in polyethylene packaging and polypropylene

packaging causing eventual decrease in their specific gravity values. These results

confirm the previous observations reported by Biemelt et al (2000). Packaging

decreased the consumption of respiratory substrate i.e starch, sugars, and organic

acids and lowered the rate of transpiration (Ding et al., 2002) due to barrier

properties resulted in higher specific gravity retention in packaged potato as

compare to control at the end of storage period.

4.2.5 Effect on Glucose

The effect of different packaging materials on glucose contents revealed

steady increase through out the storage period however, the rate of increase in

glucose contents varied with the type of packaging material. Treatment means

showed significant difference in stored potato with T1 retained maximum while T6

retained minimum glucose contents. Storage interval means also revealed non

significant difference with maximum value recorded in the last week while

minimum during first week storage. The interaction between storage intervals and

treatments revealed less significant difference at the start of storage however

significant difference have been recorded at the later stages of storage (Fig. 5).

Steady increase in glucose contents had been observed in potato during

storage however the increase was more pronounced in case of control. The rate of

increase in glucose level in control started by the fourth week and gradually

increased up to 0.333% by the end of storage. Non significant difference had been

recorded in LDPE packaging and MDPE packaging during storage period both

attained almost 0.2% glucose contents by ninth week storage. Rapid increase in

94

glucose contents had been recorded in HDPE packaging by sixth week storage the

same was also observed in potato packed in jute and nylon packaging. Least

glucose contents had been estimated in polypropylene packaged potato which

maintained the level around 0.2% by the end of storage.

Increase in the glucose contents with in the treatments during the potato

storage was found mostly consistent with the increase in the total soluble contents

(Fig. 5). The phenomenon might be due to the partial degradation of starch into

sucrose followed by the subsequent formation of more soluble sugars like glucose

and fructose (Baldwin, 2011). The degradation of insoluble starch into soluble

sugars has important inference in the tuber quality. The process founds the

availability of respiratory substrates (i.e. glucose) along with the tuber sweetness

which leads to the poor storage stability and adverse color in processed products

respectively as also been observed in the control. The amount of reducing sugar

contents in potato intending for processing is very critical since it sets the frying

color in fried potato products like chips, French fries etc. Both glucose and fructose

being reducing sugars in potato have been negatively correlated with chip fry color

(Blenkinsop et al., 2002) however the presence of glucose content are of major

food safety concern due to their active participation in toxic acrylamide formation

at elevated temperature processing (DeWilde et al., 2004). Biedermann-Brem et al.

(2003) reported that potato destined for frying, roasting or baking should contain

maximum of 0.1% reducing sugars to mitigate likely acrylamide formation. The

significant increase in glucose contents at the later stage of storage in treatments

like control, T2, T3, T5 and T8 might be due to the depletion of carbohydrates

reserves in the potato tubers close to their sprouting (Sowokinose, 1990).

95

0

70

140

210

280

350

1 7 14 21 28 35 42 49 56 63


Glu

cose

(m

g/10

0g)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 5 Glucose in potato under different packagings showing lowest contents in polypropylene during storage (LSD (0.05) for treatment = 1.970 LSD (0.05) for interval = 2.203 LSD (0.05) for interaction = 6.231)


96

Potato packed in Polypropylene, LDPE and MDPE packagings delayed the

dormancy break as compare to other treatments thus retained lower soluble sugar

contents till the end of storage. The results presented in the present study lies in

close confirmation with the findings of Fauconnier et al., (2002).

4.2.6 Effect on Total Sugars

Response of potato packaging to their total sugar accumulation was almost

consistent with the pattern of glucose accumulation during storage. The total sugar

accumulation took place at steady rate which increased till the end of storage

period. Treatment means demonstrated significant difference between packaged

potato and those placed as control, while non significant difference was recorded

between T2 and T4, T3 and T7. Storage interval means showed significant difference

between all values with maximum sugar retention at the end of storage. The

interaction between treatment means and storage intervals exhibited slow initial

increase with relatively stable values during the mid storage weeks. The

significant increase in sugar contents had been observed by the start of sixth

week storage being found more momentous in T1, T3, T5 and T8 (Fig. 6).

Maximum increase in total sugar contents was recorded in control (.82% to

1.14%) followed by the potato packed in cotton (1.089 %), nylon (1.039%) and

HDPE (1.107%) packagings. Potato packed in LDPE packaging, polypropylene

packaging, and jute packaging retained 0.925%, 0.934% and 0.959% total sugar

contents respectively.

Total sugar contents are present in potato primarily in the form of non-

reducing sucrose and reducing glucose and fructose (Blenkinsop et al., 2002).

97

750

850

950

1050

1150

1250

1 7 14 21 28 35 42 49 56 63


Tot

al s

uga

r (m

g/10

0g)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 6 Total sugar in potato under different packagings showing lowest contents in polypropylene and LDPE during storage (LSD (0.05) for treatment = 5.041 LSD (0.05) for interval= 5.636 LSD (0.05) for interaction = 15.94)


98

The increase in these soluble carbohydrates leads to the increase in total

soluble solids contents of potato tubers which was also pragmatic in the present

study. This steady increase in the total sugar was found consistent with the increase

in total soluble solids during storage which has also been reported by Vela et al.

(2003). Although the role of sucrose in browning of fried potato products is limited

but it may functions as transitory balance in starch degradation process during

storage. The hydrolysis of sucrose mediated through enzyme invertase may leads

to the formation of glucose and fructose monomers (Kumar et al., 2004).

The presence of either kind of sugars is highly undesirable for the industrial

and consumer requirement. Amongst different polyethylene packagings employed

in the present study HDPE packaging was found to be ineffective in permitting

sugar accumulation during storage which might be due to its limited permeability.

The maximum sugar retention was reported at the end of storage period in control

which might be due to their closer to dormancy break at the twilight of storage

period these findings accede the same as stated by Sowokinose (1990) and

Fauconnier et al., (2002).

4.2.7 Effect on Starch

The variation in starch contents in response to different packaging material

revealed steady initial increase followed by progressive decline during the storage

period. Data related to treatment means showed minimum starch accumulation in

T1, T3 and T8 which were found statistically similar. Maximum starch contents

were retained in T4 followed by T6 and T7. Storage interval means expressed

99

significant difference between them with non significant difference was established

between first and third week storage. Interaction between storage interval and

treatment showed maximum starch retention during second week storage. Starch

contents estimated by ninth week storage in T4 were statistically similar to those

achieved in T1 by the start of 6th week storage (Fig. 7).

Maximum starch contents were observed during second week of storage

with non significant difference was observed in all the treatments with potato

packed in LDPE and polypropylene packaging retained maximum 20.33% and

20.10% starch contents respectively. Appreciable retention of starch contents had

been observed in polypropylene packaging (17.17%) followed by LDPE packaging

(16.80%) and Jute packaging (16.57%) by the end of storage period. The

percentage depletion in starch contents by the end of storage in different packaging

systems was found minimum in polypropylene packaged potato i.e 12.5% as

compare to 21% in control.

The textural attributes in potato tubers like consistency, mealiness,

sloughing etc are largely associated to its starch properties and subsequent changes

during the processing. During physiological growth stages the sugar produced in

the potato leaves are translocated to the growing tissues and stored in the form of

starch (Fernie et al., 2002). During storage transpiration, redistribution and

respiration in potato tubers may effect their starch concentrations. The hydrolysis

of starch molecules is mediated through the activities of gluco-amylases breaking

the α-1→6 links of amylopectin generating linear molecules of amylase which

subsequently hydrolysed by invertase and amylases to produce sucrose and

reducing sugars respectively (Marchal, 1999). The starch hydrolysis however

provides sufficient energy for the growth and development of sprouts (Hentschen

and Sonnewald, 2000).

100

15

16

17

18

19

20

21

1 7 14 21 28 35 42 49 56 63


Sta

rch

(%

)

Control

Jute

Nylon

PolypropyleneCotton

LDPE

MDPE

HDPE

Fig.7 Starch in potato under different packagings depicting maximum decline in control and nylon during storage



101

In the present study maximum starch depletion in control and some other

treatments closer to sprouting confirmed the above reported findings. The use of

suitable packaging materials like polypropylene and LDPE packaging was found

efficient in sprout prevention thus retained maximum starch contents by the end of

storage period.

4.2.8 Effect on Ascorbic acid

In response to different packaging systems the ascorbic acid (AA) was

among the parameters, which decreased with the increase in storage time. The

decrease was highly significant in control as compare to all other treatments.

Treatment means revealed maximum AA retention in T4 and T6 which were found

statistically similar at 5% level of significance. Treatments T2, T7 and T8 also

maintained appreciable AA contents as compare to control. Storage Interval means

showed significant difference in their AA contents with maximum value retained

during first week storage and minimum during the last week. The interaction

between storage intervals and treatments showed substantial AA retention in

packaged potato as compare to control. AA contents observed by at the end of

storage in T4 and T6 were found greater than those identified in sixth week storage

in control (Fig. 8).

Amongst different treatments, potato packed in polypropylene packaging

and LDPE packaging retained maximum AA contents by the end of storage period.

The reductions in AA by the end of storage in PP packaging and LDPE packaging

were 26% and 29% respectively as compare to control i.e. 42%. In general the

maximum reduction in AA contents was observed during the last three weeks

storage. Moderate reduction of AA was observed in potato packed in MDPE, Jute

and Nylon i.e 31.75%, 32.5% and 33.0% at the end of storage period.

102

14

16

18

20

22

24

26

28

1 7 14 21 28 35 42 49 56 63


Asc

orbic

Aci

d (m

g/10

0g)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 8 Ascorbic acid in potato under different packagings showing highest retention in polypropylene during storage



103

Ascorbic acid is one of the most important water soluble vitamins required

in human diet and much of it is supplied by fresh fruits and vegetables. It is the

predominant vitamin in potato and of significant functional importance (Davey et

al., 2000). Depletion of ascorbic acid has been implicated with reduced nutritional

quality therefore their assured stability during storage has been focal concern for

post harvest technologists (Larisch et al., 1996). Hagg et al. (1998) reported that

AA contents significantly decreases during storage of potato. The reduction is

ascribed to the oxidation of ascorbic acid into dehydro ascorbic acid and afterward

to diketo-gluconic acid. Being water soluble vitamin and succeptable to oxidation

AA contents rapidly decreased with the increase rate of respiration and subsequent

water loss.

Facts framed in the present study revealed continuous reduction in AA

contents which was found extensive in control. The application of different

packaging systems especially of Polypropylene and polyethylene material reduced

the rate of water loss from potato and conferred barrier to the gaseous exchange

thus preventing the loss and oxidation of ascorbic acid as compare to control. The

efficacy of modified atmosphere packaging in retention of high AA contents in

fruits and vegetables have also been reported by Conte et al. (2009), Calderon et

al. (2008) and Sammi and Masud, (2007).

4.2.9 Effect on Total Glycoalkaloids

Total Glycoalkaloids (TGA) accumulation in terms of solanine equivalent

showed an increasing trend during nine week storage in all the treatments. The

104

increase in TGA was more pronounced in control as compare to packaged

potatoes. Treatment means revealed significant difference between various

packaging materials in their TGA contents. Maximum and minimum TGA contents

during storage period were identified in T1 and T7 respectively. Storage interval

means showed significant difference in their TGA contents and found maximum at

the end of storage. The interaction between storage intervals and treatments

showed maximum TGA accumulation by ninth week storage in control and

minimum in all the treatments during the 1st week storage (Fig. 9).

Results expressed on dry weight basis showed increase in TGA content in

potato tubers during storage however, in all treatment except in control the TGA

level remained under safe limit i.e. 20mg/100g f.w as suggested by

Papathanasiou et al. (1999). In general irrespective of packaging type

considerable increase in TGA contents has been recorded by fourth week

storage which continued till the end of storage. The increase in TGA in

control by the last week of storage was about eight folds (7.50 mg to 63.80

mg) as compare to around six folds (7.50 mg to 47.20 mg) increase in potato

packed in Polypropylene packaging. TGA contents increased up to 53.70

mg/100g d.w and 51.20 mg/100g d.w in Cotton and HDPE packaging

respectively by ninth week storage. Potatoes in jute, LDPE and MDPE

packaging also retained moderate TGA contents as compare to control.

The increase in TGA contents under different storage conditions and

packaging system has also been reported by different researchers. Nema et

al. (2008) reported increase in TGA contents during storage under different

packaging systems. He proposed that the color, type and permeability of the

105

5

15

25

35

45

55

65

75

1 7 14 21 28 35 42 49 56 63


TG

A (

mg/

100g

d.w

)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 9 Total Glycoalkaloids in potato under different packagings showing maximum increase in control during storage



106

packaging material effect TGA formation during storage. Similar

observations regarding the effect of different packaging materials on TGA

contents has been documented by Rosenfeld et al. (1995) and Gosselin and

Mondy, (1989). In the present study potato showed visible sprouts or closed

to sprouting retained high level of TGA contents which also confirmed the

previous findings of Sengul et al. (2004) and Kozukue et al. (2001).

4.2.2.10 Effect on Total Phenolic Contents

Total Phenolic Contents (TPC) showed initial increasing trend which

started to decline by the end of storage period. Considerable decline in TPC

was observed in control as compare to packaged potatoes. Treatment means

showed significant difference in TPC in response to different packagings. T4

and T7 maintained maximum TPC while minimum were observed in T1.

Storage Interval means expressed significant difference with maximum

determined in fifth week while minimum estimated in first week. The

interaction between treatments and storage intervals showed maximum TPC

contents in T1 and T4 during fourth and seventh week storages respectively

(Fig. 10).

Considerable increase of around 30% in TPC had been observed in all

treatments by sixth week storage, which progressively declined by the end of

storage. The decline in TPC was more significant in control, nylon, HDPE,

and cotton packaged potatoes and almost corresponded to the TPC contents

reported in first week. After ninth week storage potatoes stored in the

107

70

90

110

130

150

170

1 7 14 21 28 35 42 49 56 63


TP

C (

mg

GA

E /

100g

d.w

)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 10 Total phenolic contents in potato under different packagings showing maximum retention in polypropylene during storage (LSD (0.05) for treatment = 0.8727 LSD (0.05) for interval = 0.9757 LSD (0.05) for interaction= 2.7605 )


108

polypropylene, LDPE, Jute and MDPE packaging retained 137.23 mg,

130.23 mg, 124.07 mg and 120.50 mg TPC respectively in contrast to

control presented around 88.77 mg TPC.

Total phenolic contents are bioactive compounds responsible for

various significant physiological processes like enzyme activity, nutrient

uptake, protein synthesis (Robbin, 2003). They acts as substrate in potato

browning mediated through the activities of poly phenol oxidase (PPO)

enzymes and molecular oxygen followed by subsequent melanin formation

(Anthon and Barrett, 2002). High retention of TPC during storage is attributed

to low PPO and momentous anti oxidant activity in potatoes (Lachman et al.,

2008). During storage TPC contents in potato continued to increase

(Madiwale et al., 2011) till the on set of PPO activity. The presence of ample

molecular oxygen in control caused significant decline in TPC as compare to

other treatments. Our results indicated that packaging materials in general

and LDPE and PP packaging in particular curtail the decline in TPC as

compare to control which are also inline with the finding of Gonzalez et al.

(2004).

4.2.11 Effect on Radical Scavenging Activity

Radical scavenging activity (RSA) determined in terms of %

inhibition of DPPH showed slight initial increase followed by gradual

decrease during potato storage. The decrease in RSA was however less

pronounced in packaged potato as compare to control. Treatment means

showed T6 maintained maximum activity followed by T7, T4 and T8 while T1

demonstrated minimum activity. T2, T3 and T5 were found statistically

109

similar and expressed moderate activities during storage. Storage interval

means showed maximum activity during second and third weeks storage

which progressively decreased with time and minimum activity was found in

the last two weeks of storage. Interaction between treatment means and

storage interval showed maximum activity during second week storage in

most of treatments except in control, jute and cotton packaging.

Considerable reduction in activity had been observed between third and

fourth weeks storage (Fig.11).

Radical scavenging activity increased during first week and attained

maximum by second week in all the treatments. The decline in activity was

observed during fourth week which is more articulated in control as compare

to other treatments. Potato packed in polypropylene and polyethylene

packaging retained substantial activity after fourth week till the end of

storage period with non significant difference recorded between them. The

loss in activity after maximal second week till the end of storage in PP and

LDPE packaging was 56% and 59% in contrast to control with 69%. PP

packaged potatoes retained maximum activity i.e 23.87% followed by LDPE

and MDPE packaged potatoes with 23.23% and 22.63% by the end of

storage. The percentage loss in RSA was lesser during the last three weeks

storage as compare to initial storage weeks.

Fruits and vegetables owing to their rich vitamins and poly phenolic

contents reportedly carry high radical scavenging activity which corresponds

to their anti oxidant potential (Kondo et al., 2005). Anti oxidant have the

capacity to quench free radical and protect the biological system against

their potential detrimental effects (Diplock, 1998).

110

10

20

30

40

50

60

1 7 14 21 28 35 42 49 56 63


RSA

(%

) Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 11 Radical scavenging activity in potato under different packagings showing highest activity in polypropylene during storage (LSD (0.05) for treatment = 0.2949 LSD (0.05) for interval = 0.9209 LSD (0.05) for interaction = 2.6050)


111

Predominant anti oxidant compounds present in fruits and vegetables

includes phenolic compounds, flavonoids, carotenoids, ascorbic acids and

tocopherols (Toit et al., 2001). The maximum retention of these anti oxidants in

fruits and vegetable enable them to attain longer storage life with appreciable

nutritional attributes. Amongst different techniques to extend post harvest storage

life in perishables Modified atmosphere packaging is considered as cheap and

effective (Banaras et al., 2005). Packaging improves the retention of phenolics,

ascorbic acid and other functional component during the post harvest storage

(Barth and Zhang, 1996).

Significant correlation between phenolic contents and anti oxidant

activity (RSA) can also be distinguished between Fig 10 and Fig 11 in response

to different packagings during initial weeks of storage. The DPPH assay

employed in the present study for anti oxidant activity corresponds to the

presence of non enzymatic antioxidants like phenolics (Art and hollman, 2005)

and ascorbic acid (Kojo et al., 2004) as estimated during the storage. In the

present investigation initial increase in activity might be due to the increase in

total phenolic contents (Padda and Picha, 2008) along with the ample presence

of ascorbic acid contents in freshly cured potato. However this correlation trend

did not remain the same after the mid storage due to the earlier depletion of

ascorbic acid as compare to the stable phenolics. This phenomenon was found

more pronounced in the control as compare to packaged potatoes due to the rapid

loss of ascorbic acid during the first half of storage. Minimum percentage loss

in RSA was reported during last three weeks of storage and was specifically

attributed to packaged potatoes. The possible reason might be due to the

112

regeneration of anti oxidant compounds like ascorbic acids in potato to

counter balance the increased free radicals produced during senescence. The

better immune response in packaged potatoes maintained efficient RSA

activity at the twilight of storage period as compare to control. The improved

immune response under different packaging was also reported by Sonia and

Chavez, (2006). The use of different packaging materials on potato expressed

maximum anti oxidant activity due to greater retention of ascorbic acids, phenols

and other functional compounds. Ding et al. (2002) and Piga et al. (2002)

reported high antioxidant activity in fruits packed in modified atmosphere

packaging as compare to control as reported in the present study.

4.2.12 Effect on Polyphenol Oxidase Activity

Results pertaining to the effect of different packaging materials on the

poly phenol oxidase (PPO) activity in potato generally showed steady increase

with the extension in storage period. The increase in activity was found

prominent in control as compare to packaged potatoes. Treatment means

demonstrated maximum activity in T1 while minimum was recorded in T4 and T6

and were found statistically similar. Moderate PPO activity were observed in

treatments T2 and T8 and also found statistically similar during the storage.

Storage interval means showed significant difference in their PPO activity with

maximum and minimum values estimated on 63rd and 1st day respectively.

Interaction between storage intervals and treatments was significant with

maximum activity estimated in T1 after 1st month till the end of storage (Fig.12).

113

30

37

44

51

58

65

72

1 7 14 21 28 35 42 49 56 63


PP

O (

U/g

f.w

)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 12 Polyphenol oxidase in potato under different packagings maintaining lowest enzymatic activity in LDPE during storage (LSD (0.05) for treatment = 0.2755 LSD (0.05) for interval = 0.3081 LSD (0.05) for interaction =0.8713)


114

Steady increase with non significant difference in PPO activity had been

noticed in all the treatments till 1st month storage except in control where activity

started to increase after 21st day on wards. The PPO activity increased at rapid

rate after fourth week till the end of storage in all treatments. The enzyme activity

recorded in control on 35th day was higher than that estimated in all other

treatments by the end of storage period. Lowest PPO activity had been noticed in

PP, LDPE and MDPE packaged potatoes as compare to all other treatments and

were found statistically similar during most of storage time. PPO activity

increased more than 2-folds in control with maximum recorded PPO activity i.e

68.57 U/g in contrast to minimum 44.73 U/g in LDPE packaged potato at the end

of storage time.

PPO activity increases in potato due to the availability of substrate and its

subsequent oxidation during storage. The non significant changes during the 1st

month storage in most of the treatments might be due to absence of physical

damages due to their appropriate curing and subsequent careful post harvest

handling as also observed by Nourian et al. (2003). The increased PPO activity in

fruits and vegetable during post harvest storage might be attributed to moisture

loss and senescence (Bryant, 2004). In the present study application of different

packaging materials effectively maintained modified atmospheric conditions

around potato as compare to control resulted in lower moisture loss and limited

oxygen availability for poly phenol oxidations.

115

The variation in PPO activity with in different packaging materials might

be attributed to their type and permeability (Rakotonirainy et al., 2001). The

significant increase in the PPO activity in different treatments by 4rth week till

the end of storage might be attributed to the high substrate availability yet

packaging materials conferred barrier properties to substrate oxidation resulted in

low eventual activity as compare to control. Kader, (2002) reported substrate

inhibition for PPO enzymes under modified atmosphere packaging which lead to

low PPO activity during storage. These effective barrier properties in different

packaging materials like polyethylene, polypropylene, polystyrene have also been

reported by Joyce and Patterson (1994).

4.2.13 Effect on Peroxidase Activity

Effect of different packaging materials on peroxidase (POD) activity in

potato showed a steady increase in all the treatments during storage however the

increase was highly prominent in control as compare to other treatments (Fig.

13). Treatments means revealed maximum activity in T1 while minimum in T6.

Non significant difference had been observed in T2 and T3 whereas T5 and T8

were also found statistically similar. Storage interval means showed maximum

and minimum activity during last and first week respectively. Interaction between

storage intervals and treatment was significant with maximum activity estimated

in T1 on 49th day onwards till the end of storage (Fig.13).

116

In general POD activity steadily increased in the potato tubers during the

storage and found crumb consistent to their PPO activity. Maximum activity

POD activity (32.40 U/100g) was estimated in control and minimum (23.20

U/100g) in LDPE at the end of storage. PP and MDPE packaging retained

comparatively low POD activity 23.43 U/100g and 26.47 U/100g respectively

during the same storage periods. In comparison the POD activity estimated in T4

and T6 at the end of storage was found lower than that calculated in T1 on 42nd

day storage.

Enzymatic browning in potato may cause substantial loss by deteriorating

nutritional and sensorial attributes during storage. The phenomenon is primarily

associated with the activities of peroxidase and polyphenol oxidase enzymes

(Loaiza and Saltveit, 2001). POD being thermally stable and omni present in

different part of plants has wide range of substrate based activity than PPO

(Anthon and Barrett, 2002). The increased POD activity is associated with the

oxidation of phenolic compounds under physiological stress causing decay and

loss of quality during storage (Ding et al., 2006). In addition they also have

known to exhaust immune system by degradation of natural anti oxidants i.e

peroxides and consequent liberation of free radicals (Rojas et al., 2007). Both

these processes mediated through peroxidase activity accelerate browning in

potatoes and affect the ultimate postharvest storage life.

117

12

16

20

24

28

32

36

1 7 14 21 28 35 42 49 56 63


Per

oxi

das

e (U

/100

g f.

w)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 13 Per oxidase in potato under different packagings maintaining lowest enzymatic activity in polypropylene and LDPE during storage (LSD (0.05) for treatment = 0.2717 LSD (0.05) for interval = 0.3038 LSD (0.05) for interaction = 0.8593)


118

POD is considered thermally more stable than PPO thus their activity inhibition

is considered as index of proper blanching in food processing. Aydin and

Kadioglu (2001) reported increased POD activity in fruits and vegetables under

stress conditions and with the progression in their physiological stages i.e.

ripening, senescence which has also been observed in different treatments at the

end of storage period.

Application of different packaging materials maintained low POD activity

as compare to control in potato at ambient temperature storage due to low

available oxygen required for the oxidation of phenols and peroxides. The

increased POD activity by the end of storage particularly in control might be

attributed to the physiological stress in the form of senescence and sprouting in

potato. The increased POD activity at senescence has also been reported by

different scientists in potato (Afify et al., 2012) mandarin (El-hilali et al., 2003),

Cherry (Tian et al., 2004) which confirms the observations presented in the

present study.

4.2.14 Effect on Chip Moisture Contents

Progressive increase in chip moisture contents (CMC) was recorded in

response to different packaging material during storage. Treatment means

showed maximum moisture contents in the chip processed from T1 followed by

T2 while, minimum moisture contents identified in T6. In general non significant

difference observed between all other packaging materials. Storage interval

means showed maximum CMC during the last week storage while during first

month storage the CMC remained statistically similar in all the treatments. The

119

interaction between treatments and storage revealed maximum chip moisture

contents in T1 at the end of storage time (Fig.14).

Chip moisture contents increased in all the treatments with the

progression in storage time however, the change was found more pronounced in

control as compare to packaged potatoes. The maximum percentage increase in

CMC in control till the end of storage was about 50% in control as compare to

21.5% and 23.5% in LDPE and PP packaged potato respectively. Generally

packagings retained lower chip moisture contents as compare to control till the

end of storage time.

Mass transfer during potato chips processing was associated with the

moisture loss and oil uptake during frying. The moisture contents diffused out of

the cellular matrix leaving behind capillary pores which were consequently filled

by oil (Mellema, 2003). The increase in fat and decrease in moisture contents

during frying has also been reported by Kita et al. (2004). High moisture contents

in potato chips are very critical since it cause sogginess and hydrolytic rancidity

due to free fatty acid formation during storage.

Frying has been described as immersion of food products in edible oil

heated at temperature above the boiling point of water (Hubbard and Farkas, 1999)

thus precisely termed as dehydration process. The initial moisture content in potato

chips before frying was around 74.50% with minor fat content (0.8% on dry

weight basis). After frying the Chip moisture contents decreased up to 1.24 %

while the fat contents increased by 30%. Potato with high specific gravity and dry

matter contents were reported to produce potato chips with low moisture contents

120

1

1.4

1.8

2.2

2.6

1 14 28 42 56 70


Ch

ip m

oist

ure

con

ten

ts (

%)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 14 Chip moisture contents in potato under different packagings showing highest increase in control during storage (LSD (0.05) for treatment = 0.03624 LSD (0.05) for interval = 0.03139 LSD (0.05) for interaction = 0.08877)


121

(Pinthus et al., 1995). Although non significant difference observed in CMC

value in response to different packaging application but found effective in the

preparation of potato chips with lower moisture contents as compare to control.

In the present investigation, the packaged potatoes maintained high specific

gravity value during storage thus produced potato chips with low moisture

contents which also confirmed the previous findings reported by Mehta and

Swinburn (2001) and Aguilera et al. (2000).

4.2.15 Effect on Chip Fat Absorption

Chip fat absorption (CFA) increased with the increase in storage period in

all the treatments. Treatment means demonstrated maximum CFA in T1 and

minimum in T4 and T6, while non significant difference observed in most of the

other treatments. The storage interval means showed maximum CFA during the

end of storage period while minimum was found during the early weeks of

storage. The interaction between storage intervals and treatment means showed

maximum CFA during the last of storage in T1 followed by T3. The maximum

percentage increase in CFA was observed in control during the last month of

storage (Fig.15).

CFA increased in all the treatments during storage period and found

maximum in control and minimum in polyethylene (LDPE, MDPE and HDPE) and

polypropylene packaged potatoes. The percentage increase in control was around

33.88% in control as compare to 17.75%, 18.41% and 19.14% in LDPE, MDPE

and HDPE packagings respectively. The application of different packaging

materials retained low CFA as compare to control.

122

30

33

36

39

42

45

48

1 14 28 42 56 70


Ch

ip f

at a

bso

rpti

on (

%)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 15 Chip fat absorption in potato under different packagings showing maximum value in control during storage (LSD (0.05) for treatment = 0.4579 LSD (0.05) for interval = 0.1413 LSD (0.05) for interaction = 1.1220)


123

Oil is the major source of flavor enhancer in potato chips but its high level

is of great concern for the producer and consumer for economic and food safety

point of view respectively. Oil absorption during frying in potato chips depends on

different factors like tuber specific gravity (Mehta and Swinburn, 2001), pre drying

(Pedreschi and Moyano, 2005), modification in size and thickness (Gamble and

Rice, 1988), frying temperature (Mellema, 2003), modification in frying

techniques (Mehta and Swinburn, 2001) and frying medium (Berry et al., 1999),

and potato chips coatings (Williams and Mittal 1999). Kita, (2002) reported that

potatoes with high specific gravity and starch contents produce chips with low oil

contents during frying. Potatoes stored in polyethylene and polypropylene

packaging retained high specific gravity and appreciable starch contents thus

produced chips with lower fat contents as compare to control. The inverse

proportion between tuber specific gravity and fat absorption has also been reported

by Hagenimana et al., (1998) which confirmed the present findings.

4.2.16 Effect on Chip Color

Chip Color (CCL) recorded in terms of approximate L-value showed steady

decrease with the increase in storage time. The treatments means illustrated

minimum CCL value in T1 and T3 while all other treatments were found

statistically similar (at α= 0.05). Storage interval means showed maximum CCL

values during the first month and minimum at the end of storage. The interaction

between treatments and storage intervals showed maximum CCL value during the

start of storage in all the treatments and minimum in T1 and T3 at the end of storage

period(Fig.16).

124

56

58

60

62

64

66

1 14 28 42 56 70


Ch

ip c

olor

(L

-val

ue)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 16 Chip color in potato under different packagings showing highest value in polypropylene during storage (LSD (0.05) for treatment = 1.0290 LSD (0.05) for interval = 0.3173 LSD (0.05) for interaction = 2.5200)


125

Packaged potatoes expressed appreciable CCL value during the storage as compare

to control. CCL values obtained in LDPE (61.75) and MDPE (60.67) packaged

potato at the end of storage was similar to that recorded in control during 28th and

42nd days respectively. Maximum CCL value (62.00) was identified in

polypropylene packaged potatoes however remained statistically similar to the

most of other treatments at the end of storage.

Chip Color is the most important quality parameter sternly related to the

consumer perception for the product acceptance (Segnini et al., 1999). Potato chip

color is the consequence of Maillard reaction primarily related to the presence of

reducing sugars, protein, frying temperature and duration (Mackay et al., 1990). In

addition the CCL value is an important index of toxic acrylamide formation in

potato during high temperature processing (Stadler et al., 2002).

CCL values in the present investigation were quantified on the basis of

approximate L-values as described in fry color chart by British Potato Council

(BPC, UK). L* is the luminance having colorimeteric value ranges between 0

(Black) to 100 (Light) however the L-value for potato chips color presented in the

fry color chart ranged between 65 (Grade-I) to 49 (Grade-V). In general the CCL

values remained statistically similar in response to most of the packaging

applications however found minimum in control as compare to all other treatments.

Since the frying temperature and duration remained constant factors in potato

processing thus presence of reducing sugars being the major determinant of CCL

values during storage. Potato with low reducing sugar contents retained maximum

CCL value as happened in packaged potatoes during storage. The correlation

126

between reducing sugar contents and potato chip color has also been reported by

different researchers like De Wilde et al. (2004), Biedermann-Brem et al. (2003)

and Rodrigues- Saona and Wrolstad, (1997).

4.2.17 Effect on Chip Crispiness

Chip crispiness (CCR) scores showed a steady increase followed by final

decrease in all the treatments however the rate of decrease in CCR scores was

found lower in packaged potatoes as compare to control. Treatment means

revealed non significant difference in T4, T6, T7 and T8 while T2, T3 and T5 were

also found statistically similar at 5% level of significance. Storage interval means

showed initial increase in CCR scores which remained persistent during the most

of storage time and found minimum during the end of storage. The interaction

between treatments and storage intervals showed maximum CCR scores in T4 and

T8 on 42nd and 28th days respectively. Minimum CCR scores were identified in

control in T1 at the end of storage (Fig.17).

CCR scores expressed in T4 and T6 at the end of storage were found similar

to those identified on 28th day storage in control. Over all percentage decline in

CCR scores was found maximum (45.76%) in Control and minimum (16.14%) in

Poly propylene packaged potatoes during storage. Potato chip texture is often

described as crispiness which is an important sensorial attribute for consumer’s

appreciations. Eminent crispy structure develops in potato chip due to the

hardening of chip crust during frying at elevated temperature (Pedreschi et al.,

2001) Crispiness in potato chips is dependent on the excellence of raw material and

improved processing techniques. Potato tubers with high specific gravity and dry

127

2

2.5

3

3.5

4

4.5

5

1 14 28 42 56 70


Chip

cri

spin

ess

(sco

res)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 17 Chip Crispiness in potato under different packagings showing highest value in polypropylene and LDPE during storage (LSD(0.05) for treatment= 0.1788 LSD(0.05) for interval= 0.1548 LSD(0.05) for interaction= 0.4379)


128

matter contents reported to produce potato chips with high crispiness value

predominantly influenced by starch and non starch polysaccharides (proto pectin)

contents (Kita, 2002). Jaswal, (1991) reported that the potato with high specific

gravity contain high molecular weight, stable and compact polysaccharides (starch,

pectin etc.) contents preventing their integrity thus contributing to their appreciable

textural configurations during frying. In the present study the potato tubers with

high specific gravity value maintained appreciable CCR scores in the fried

products. Although CCR scores with in most of packaging materials remained

statistically in significant however potatoes with high specific gravity value

produced chips with appreciable CCR value as compare to control which

confirmed the findings reported by the researchers above.

4.2.18 Effect on Chip Flavor

Chips flavor (CFL) estimated as scores recorded by the judges showed an

initial increase and eventual decreasing trend in all the treatments during the

storage. The treatment means exhibited maximum CFL scores recorded in T6, T7

and T4, non significant difference was recorded between T2 and T8 while

minimum CFL scores were identified in T1, T3 and T5. The means of storage

intervals showed maximum CFL during the mid storage intervals while minimum

were articulated during the start and end of the storage. The interaction between

storage intervals and treatments showed minimum (2.73/5.00) and maximum

(4.17/5.00) scores in T1 and T6 respectively during storage (Fig.18). In general

CFL scores increased in all the treatments after 28th days storage which started to

decline after 56th days storage in most of the treatments. Potatoes stored in

129

2.5

3

3.5

4

4.5

5

1 14 28 42 56 70


Ch

ip f

lavo

r (s

core

s)

Control

Jute

Nylon

Polypropylene

Cotton

LDPE

MDPE

HDPE

Fig. 18 Chip Flavor in potato under different packagings showing highest value in polypropylene during storage

(LSD (0.05) for treatment = 0.1480 LSD (0.05) for interval l= 0.0456 LSD (0.05) for interaction = 0.3624)


130

polyethylene and polypropylene packaging retained appreciable CFL scores by the

end of storage period as compare to control.

Flavor is the sensory impression of food detected by the blend of taste and

smell senses. It is the over all resultant impression derived by the taste buds in

mouth and aroma detected by olfactory epithelium in nose. Flavor evolution in

potato chips is primarily attributed to the oil uptake and corresponding volatile

formations during thermal processing (Martin and Ames, 2001). In the present

study generally CFL scores were found in consistent with the other quality

attributes in potato chips. The maximum CFL scores were identified in LDPE,

MDPE and PP packaged potatoes as compare to control.

4.3 EFFECT OF DIFFERENT LIGHT SOURCES ON THE QUALITY

ATTRIBUTES OF POTATO

The objective of the second experiment of 2nd phase was to identify most

appropriate light source for best potato variety “Lady Rosetta” with appreciable

retention of different quality parameters. Potato tubers were placed for 27 days at

ambient storage (25± 3oC) under different light sources i.e. blue, fluorescent,

green, mercury and red along with dark storage which also served as normal

control. Physico-chemical, functional and processing attributes were studied in

potato tubers and potato chips at three and seven days interval respectively.


In response to different light sources weight loss (%) increased in all the

treatment with time however maximum weight loss (%) was reported in T2 and

minimum in T6 at the end of storage. Treatment means showed minimum weight

131

loss (%) in T6 followed by T3 and T4 which were found statistically similar.

Maximum weight loss was recorded in T2 followed by T5 and T1 which were also

found statistically at par. Interaction between treatments and storage intervals

showed maximum weight loss (%) in all the treatments at the end of storage time

except in control (Fig.19).

In general non significant difference was observed with in the treatments by

the mid storage period, which was trailed by significant increase under fluorescent

light (2.958%), blue light (2.908%) and red light (2.918%) till the end of trial.

Steady increase in weight loss was found under mercury (2.450%) and green

(2.474%) light exposures with minimum increase recorded in tubers placed under

dark (2.276%). Gachango et al. (2008) reported minimum weight loss in potato

stored in dark as compare to those placed under indirect sunlight and direct

illuminations. Kabira and Lemaga (2003) anticipated the use of dark rooms for

potatoes to decrease the eventual weight loss during storage.

International Potato centre (CIP, 1997) proposed the storage of potato

under indirect sunlight for maintaining tuber quality. Walingo et al. (1995) also

reported lower weight loss in potato under dark as compare to different light

sources. In the present study significant weight loss (%) in potatoes under

fluorescent, blue and red lights might be attributed to their high level of energy

resulted in the elevated rate of respiration and eventual increased weight loss (%)

as compare to dark and other light sources which was found in line with the

findings of the researchers reported above.

132

0

0.5

1

1.5

2

2.5

3

3.5

1 3 6 9 12 15 18 21 24 27


Wei

ght

loss

(%

)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 19 Weight loss in potato under different light sources showing minimum loss in dark followed by mercury during storage (LSD (0.05) for treatment = 0.01617 LSD (0.05) for interval = 0.02087 LSD (0.05) for interaction = 0.05112)


133


Steady increase in the total soluble solids (TSS) observed in all the

treatments under different light illuminations. The treatment means showed close

statistical similarities between different light exposures. Least increase was

observed in Dark storage while maximum TSS accumulation was observed in T2

and T5 which were found statistically similar. Moderate TSS increase was found in

T3 and T4 which were statistically similar (α-0.05) during storage. The storage

interval means revealed non significant difference between the treatments during

the 1st week and found significant at the end of storage (Fig. 20).

Highest TSS accumulation was noticed in potato placed under red light

(5.98 obrix) and flourescent light (5.97 obrix) followed by Blue light (5.96 obrix).

TSS accumulation remained statistically similar in green light, mercury light and

dark at the end of storage. The percentage increase in TSS during the trial

remained maximum (6.20%) under fluorescent light as compare to minimum

(3.95%) in dark and green light storage.

The increase in TSS is attributed to the hydrolytic conversion of insoluble

starch in to soluble sugars during storage (Kittur et al., 2001). Exposure of tubers

to high energy illuminations (flourescent, blue and red) may cause increase in

starch hydrolysis due to physiological stress eventually increased the total soluble

contents as compare to other storage conditions. Nema et al. (2008) reported

elevated level of soluble sugars due to tuber stress and exposure to different high

energy light sources, this elevated level of reducing sugars particularly in the form

of galactose served as precursor for alkaloids formation (Percival et al., 1993). In

the present study exposure of potato tubers to high energy lights caused increased

134

5.5

5.6

5.7

5.8

5.9

6

1 3 6 9 12 15 18 21 24 27


Tot

al s

olu

ble

sol

ids

( oB

rix)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 20 Total soluble solids in potato under different light sources showing lowest increase in dark and green light during storage (LSD (0.05) for treatment = 0.005112 LSD (0.05) for interval = 0.002357 LSD (0.05) for interaction = 0.005774)


135

starch degradation and favored the formation of soluble sugars and retained higher

TSS accumulation as compare to dark which corresponded the finding of

researchers reported above.

4.3.3 Effect on Color

Highly significant decrease in color scores was observed under different

light sources as compare to dark storage. The treatment means showed significant

difference between color scores in response to different illuminations. Minimum

color scores were reported in T2 followed by T1 and T5 while maximum scores

were observed in T6. The storage interval means revealed significant difference

with maximum color scores reported during the start of trial and minimum at the

end of storage. The interaction between treatment means and storage intervals

showed appreciable color scores during the start of experiment in all the treatments

and started to decline after 1st week storage except in T6 (Fig.21).

Potato placed under dark storage retained maximum color scores through

out the storage, color scores retained by dark storage at the end of storage were

found greater than those tubers placed under fluorescent light on 3rd day of

continuous illumination. In general color scores remained unaffected under dark

storage during the complete research trial and percentage decrease was only around

4% in contrast to 77% decrease in fluorescent illumination. Amongst different

treatments green and mercury illuminations maintained appreciable color scores

where the percentage decrease was found 21% to 29% respectively. Storage of

tubers under blue and red illuminations also presented poor color scores i.e.

2.83/8.00 and 3.00/8.00 respectively by the end of storage period.

136

1.5

2.5

3.5

4.5

5.5

6.5

7.5

8.5

1 3 6 9 12 15 18 21 24 27


Col

or (

scal

e)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 21 Color in potato under different light sources showing highest scores in dark during storage (LSD (0.05) for treatment = 0.0503 LSD (0.05) for interval = 0.1819 LSD (0.05) for interaction = 0.4457)

137

Estimation of color scores in potato tuber in response to different light sources was

carried out with the help of scale designed by Grunenfelder et al. (2006) for Dark

Red Norland variety with inverse modification (8 = Normal, 1 = Greened). The

discoloration in potato tuber in response to different light sources is primarily

associated with the chlorophyll formation in periderm (Pavlista, 2001). Percival,

(1999) reported increase in chlorophyll contents in potato tubers in response to

different light sources and found maximum chlorophyll accumulation in

fluorescent and minimum in mercury illuminations. Edward and Cobb, (1997)

stated that the rate of chlorophyll synthesis in potato tuber is highly effected by the

light exposure. Griffith et al. (1994) reported dark green patches in potato tuber

due to stress imposed by sunlight. In the present investigation the substantial

retention of high color scores in tuber stored in dark as compare to different

illumination confirmed the finding of researchers reported above.


The general trend was an increase in glucose contents in all treatments

during the storage which remained steady under dark storage. The treatments

means exhibited maximum increase in T2 and T5 and were found at par statistically.

Significant increase in glucose contents were also recorded in T2. Minimum

glucose retention was demonstrated in T6 followed by T3 and T4. Storage interval

means showed minimum glucose contents at the start and maximum at the end of

storage period. Interaction between treatments and storage intervals revealed

significant increase in glucose contents during the last week of storage in T1, T2

and T5 (Fig. 22).

138

0

30

60

90

120

150

180

210

1 3 6 9 12 15 18 21 24 27


Glu

cose

(m

g/10

0g)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 22 Glucose in potato under different light sources showing highest increase in florescent light during storage



139

Increase in glucose contents in tubers started from the start of storage in blue,

fluorescent and red illuminations and remained two folds than the rest of

treatments by the end of 3rd week. Green and mercury light retained moderate

increase in glucose contents and were found statistically insignificant during most

of the storage period. Glucose contents recorded at the end of storage in dark were

found lower than that recorded in fluorescent and red lights by the end of 2nd week

and found minimum through out the storage period. The glucose contents

accumulation in potato tubers is associated with the starch hydrolysis during the

storage period (Sonnewald 2001) and accelerated during tuber stress due to

exposure to high energy illuminations (Percival, 1993). The greater increase in

glucose contents during storage under fluorescent, red and blue lights as compare

to other treatments might be due to the increased relative degradation of starch

contents. The results were also in close confirmation with the findings of Chen and

Setter (2003) who reported decreased glucose contents in potato tubers under shade

storage.

4.3.5 Effect on Total Sugar

Total sugar accumulation in potato tubers in response to different

illuminations was increased constantly during storage and found in consistent with

the trend achieved in glucose contents (Fig 23). The treatment means showed

maximum sugar accumulation in T2 followed by T1 and T5 which were found

statistically same (α-0.05). Storage interval means showed non significant increase

in sugar content during 1st week followed by prominent increase during the rest of

storage period. Interaction between treatments and storage intervals showed

maximum sugar accumulation in T2 while minimum estimated in T6 at the end of

trial (Fig. 23).

140

800

840

880

920

960

1000

1 3 6 9 12 15 18 21 24 27


Tot

al s

uga

rs (

mg/

100g

)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 23 Total Sugar in potato under different light sources showing highest increase in florescent light during storage (LSD (0.05) for treatment = 2.602 LSD (0.05) for interval = 3.359 LSD (0.05) for interaction = 8.229)


141

Total sugars increased under all illuminations and found minimum in tubers

stored under dark. The increase in sugar was highly significant under fluorescent, blue

and red lights with steady increase also observed under mercury and green light.

Storage under dark by the end of storage period retained lower sugar contents than that

estimated in fluorescent, blue and red lights by the end of 1st week storage. In terms of

their sugar accumulation blue and red illumination were found statistically same

during most of the storage period.

Continuous exposure of potato tubers to different light sources caused sugar

accumulation due to starch hydrolysis mediated through tuber stress (Percival, 1999).

The initial increase in sugar contents in response to different illuminations during

storage has also been reported by Olson (1996). Dale et al. (1993) reported elevated

sugar contents in potato exposed to continuous illumination as compare to those

placed under dark. The moderate sugar contents identified in green and mercury lights

might be due to lesser starch hydrolysis owing to their low energy spectrums which

has also been confirmed by Nema et al. (2008).


Data related to starch contents in response to different illumination revealed

non significant initial increase followed by progressive decline with the storage period.

The treatment means showed minimum starch contents in T1, T2 and T5 and were

found statistically similar at 5% level of significance. T6 retained maximum starch

contents at the end of storage followed by T3 and T4 which were also found at par

statistically. The storage interval means showed maximum starch content during 1st

week storage and than declined significantly by the end of storage period. The

interaction between treatments and storage intervals showed minimum starch contents

in T1, T2 and T5 on last day storage (Fig. 24).

142

17.5

18

18.5

19

19.5

20

1 3 6 9 12 15 18 21 24 27


Sta

rch (%

)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 24 Starch in potato under different light sources showing highest decline in florescent and red light during storage (LSD (0.05) for treatment = 0.0996 LSD (0.05) for interval = 0.1287 LSD (0.05) for interaction = 0.3151)


143

In general after an initial increase all the treatments experienced starch depletion in

response to different illuminations however the percentage decrease was highly

prominent in blue (8.75%), fluorescent (9.0%) and red (8.86%) lights as compare

to other treatments. The minimum percentage decline in starch contents were

reported in dark (5.80%) followed by green (6.25%) and mercury (7.0%)

illuminations.

The initial increase in starch contents might be due to tendency of freshly

cure potato to accumulate dry matter primarily in form of starch (Kaul et al.,

2010). The metabolism of carbohydrate contents during post harvest storage is

very important both in table and processing potato varieties (Herrman et al., 1996).

The quality of potato tubers keep on changing due to depletion of starch and

formation of corresponding sugars during storage (Nourian et al., 2003). Nema et

al. (2008) reported that continuous exposure of tuber to high energy wavelengths

cause physiological stress characterized by increased rate of respiration followed

by starch depletion. Maximum starch depletion in potato under different high

energy illuminations (fluorescent, blue and red) during the present study confirmed

the findings reported above. General decline in starch content in different

treatments might be attributed to the consumption of respiratory substrate (starch)

during post harvest storage.

4.3.7 Effect on Ascorbic Acid

General trend showed reduction in ascorbic acid (AA) contents in response

to different illuminations during the storage time. The treatment means showed

significant difference amongst all with maximum and minimum AA retention in T6

144

and T2 respectively. The storage interval means showed significant difference in

AA contents with maximum retention at the start and minimum recorded at the end

of trial. The interaction between treatments and storage intervals showed

appreciable retention of AA in T6 followed by T3 during most of the storage

period. Significant reduction in AA contents was observed in T2 with in three days

illumination (Fig. 25).

In the present study exposure of potato tubers to different illuminations

caused significant reduction in AA. The reduction was highly significant in T2

where the percentage decline was around 10% with in three days which escalated

up to 29% by the end of one month storage. Exposure of tubers to blue and red

lights presented 23.5% and 25% decline in AA contents respectively. Moderate

reduction of AA contents also reported in case of green (17.2%) and mercury

(19.6%) illuminations. Dark storage of potato retained maximum AA contents and

percentage decline was observed around 11.8 % only. Ascorbic acid is considered

as important dietary antioxidant vitamin and known to decline during post harvest

storage period in fruits and vegetables (Lee and Kader 2000) due to oxidation (Piga

et al., 2003), photo degradation (Leskova et al., 2006) or utilization as respiratory

substrate (Kader, 2002). Owing to its high degree of sensitivity it is considered as

an imperative index of quality in fruits and vegetable during storage and food

processing (Ozkan et al., 2004). Dale et al. (2003) reported that ascorbic acid

contents decrease in horticultural produce due to light exposure, heat; low relative

humidity and prolonged storage time hence are critical considerations in

optimizing suitable post harvest storage conditions. Similar results

145

16

18

20

22

24

26

1 3 6 9 12 15 18 21 24 27


Asc

orbic

aci

d (m

g/10

0g)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 25 Ascorbic acid in potato under different light sources showing highest retention in dark followed by green light during storage (LSD (0.05) for treatment = 0.1696 LSD (0.05) for interval = 0.2189 LSD (0.05) for interaction = 0.5362)


146

were reported in the present study by maximum retention of ascorbic acid in dark

storage as compare to different illuminations.

4.3.8 Effect on Chlorophyll

Chlorophyll contents continue to increase significantly during the storage

time in response to different light exposures (Fig. 26). The treatments means

showed maximum chlorophyll accumulation in T2 followed by T5 and T1 which

were found statistically similar (α-0.05). Considerable chlorophyll contents were

estimated in T5 followed by restrained contents identified in T3 and T4 which were

found statistically at par (α-0.05). Chlorophyll contents remained at minimum level

in T6. The interaction between treatments and storage intervals demonstrated

minimum contents witnessed in most of the treatments by the end of 1st week

storage while maximum were estimated in T1, T2 and T5 by the end of last week

(Fig. 26).

Chlorophyll contents increased progressively under fluorescent, blue and

red illuminations and showed steady increase under dark during the storage period.

The contents started to increase in high energy illuminations with in 1st week of

storage particularly in fluorescent light where the percentage increase was 53.0%

more than that identified in dark at the end of storage (45.4%).

Maximum contents were recorded in T2 (3.64 mg/100g) with significant

linear increase in the chlorophyll contents i.e. more than six folds over the

complete storage period. Response of potato in exposure to red (2.99 mg/100g) and

blue (2.88 mg/100g) illuminations accumulated considerable chlorophyll contents

as compare to mercury (1.99 mg/100g) and green (1.66 mg/100g)

147

0

0.5

1

1.5

2

2.5

3

3.5

4

1 3 6 9 12 15 18 21 24 27


Chl

orop

hyl

l (m

g/10

0g d

.w)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 26 Chlorophyll in potato under different light sources showing maximum increase in florescent and blue lights during storage (LSD (0.05) for treatment = 0.1617 LSD (0.05) for interval= 0.2087 LSD (0.05) for interaction = 0.5112)


148

lights at the end of storage. In general all different kind of illuminations caused

increase in chlorophyll contents at erratic pace with no indication of termination

during the complete trail.

Exposure of potato tubers in response to light caused the formation of

chlorophyll in cortical parenchyma due to conversion of amyloplast in to

chloroplast (Pavlista, 2001).The extent of greening in retail outlets emphasizing the

development and realization of appropriate light source to maintain desirable

quality attributes in potato tubers. Percival, (1999) compared the response of

different tuber varieties to various light sources and reported irrespective of variety

maximum chlorophyll accumulation under fluorescent and sodium illuminations as

compare to mercury light and dark. Grunenfelder et al., (2006) exposed different

colored potato varieties to fluorescent lighting of similar intensity and found

discoloration of periderm in all of them due to significant increase in chlorophyll

contents. The present study demonstrated significant chlorophyll accumulation in

potato tubers due to various illuminations. Our results concluded that the

replacement of fluorescent light with green or mercury illuminations in retail

displays for time being might cause reduction in potato greening as also reported

by researchers above. Dark potato storage demonstrated appreciable tuber quality

due to minimum chlorophyll accumulation thus might be recommended for

prolonged tuber storage which has also been concluded by different researchers

like Nema et al. (2008) Rita et al. (2007) and Edward and Cobb (1997).


Data related to Total Glycoalkaloids (TGA) showed progressive increase

under different illuminations during storage. The treatments means showed

149

significant difference between their TGA contents with maximum retention in T2

followed by T1 and T5 while minimum TGA contents were identified in T6. The

storage interval means showed minimum TGA contents during 1st week and than

progressively increased till the end of storage. Significant interaction was observed

between treatments and storage intervals with highest TGA contents estimated in

T2 during last week while least were identified in all treatment by 1st week storage

(Fig. 27).

The TGA contents increased through out the storage period irrespective of

treatments however the rate of increase in TGA contents was higher in fluorescent,

blue and red light illuminations. The increase in TGA contents under fluorescent

light was maximum (79.92 mg/100g d.w) and estimated around 8-folds as compare

to 2.5-folds increase in dark by the end of storage period. The increase in TGA

contents under fluorescent illumination at the end of storage surpassed the safe

limits described for human intake i.e 20mg /100g f.w (Mensinga et al., 2005). In

general percentage increase in TGA with in different storage interval was found

highest in last week. Minimum TGA accumulation was identified in dark (18.90

mg/100g d.w) followed by mercury (28.03 mg/100g d.w) and green (30.93

mg/100g d.w) illuminations.

TGA contents estimated in the present study in terms of solanine equivalent

are affected by different illuminations and also associated with the elevated

chlorophyll contents. Grunenfelder et al. (2006) studied the increase in TGA and

150

0

15

30

45

60

75

90

1 3 6 9 12 15 18 21 24 27


TG

A (m

g/10

0g d

.w)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 27 Total glycoalkaloids in potato under different light sources showing highest increase in florescent light during storage (LSD (0.05) for treatment = 0.4137 LSD (0.05) for interval = 0.5341 LSD (0.05) for interaction = 1.3080)


151

chlorophyll contents under fluorescent light and concluded parallel but

independent development of both compounds. Rita et al. (2007) compared TGA

accumulation in potato tubers under different illuminations during postharvest

storage. He found maximum and minimum TGA contents under fluorescent light

and dark respectively. Percival et al. (1999) investigated light-induced TGA

accumulation in potato tubers under four different illuminations. He declared

maximum contents under fluorescent and sodium lights and minimum under dark.

Our results in the present study also confirmed the pervious finding as steady TGA

contents in dark as compare to significant increase under fluorescent light. The trial

also exhibited parallel association between chlorophyll and glycoalkaloids

accumulations in potato tubers. The process is however found independent due to

increased TGA contents in blue to red and green to mercury lights having less

corresponding chlorophyll contents during the same storage period.

4.3.10 Effect on Total Phenolic Contents

Total phenolic contents (TPC) increased steadily during the storage period

in response to different illuminations however the increased is followed by

considerable decline in T1, T2 and T5.In general non significant difference in

treatment means was observed except in T4 and T6. The storage interval means

however showed significant difference with maximum and minimum TPC

identified in the end and start of experiment. Highly significant interaction was

observed between treatments and storage intervals after the mid storage period

(Fig. 28).

Total phenolic contents increased during the start of storage in all the

treatments and the initial rise was found independent of different illuminations. I

152

110

120

130

140

150

160

1 3 6 9 12 15 18 21 24 27


TPC

(m

g G

AE

/100

g d.w

)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 28 Total phenolic contents in potato under different light sources showing maximum retention in green light during storage (LSD (0.05) for treatment = 0.5211 LSD (0.05) for interval = 0.6727 LSD (0.05) for interaction = 1.6480)


153

general non significant difference was observed in most of the treatments till 9th

day storage. TPC contents significantly increased in all the treatments by the end

of 2nd week storage which was followed by progressive decline in fluorescent, blue

and red illuminations during the last week of storage. TPC increased continuously

under green, mercury and dark storage with no sign of cessation during the storage

period, however the rate of TPC increase during the 1st half of storage was found

slower as compare to high energy illuminations (T1, T2 and T5).

Total phenolic contents showed varied retention under different

illuminations during storage period. Light is considered as an important factor

causing the biosynthesis of phenolic compounds facilitated by the activity of

phenylalanine ammonia-lyase enzymes (Lewis et al.,1998) In addition it is also

known to initiate the anthocyanin and chlorogenic biosynthesis pathways

contributing to the total phenolic contents in potato tubers (Griffiths, 1995). The

swift initial increase in TPC under different light sources and steady TPC under

dark partially confirmed the findings reported by different researchers above and

negated the investigation reported by Reyes and Zevallos, (2003) who reported no

considerable effect of light on the TPC accumulation in purple-fleshed potato

tubers. The possible reason might be due to the varietal difference and lack of

comparative study under different illuminations. Tubers placed under green and

mercury lights retained appreciable TPC at the end of storage probably due to lack

of tuber stress and moderate respiration rate. The decline in TPC contents under

high energy illumination at the end of storage might be attributed to the tuber stress

due to high metabolic rate, increased rate of respiration causing eventual decline in

total phenolic contents.

154


Radical scavenging activity (RSA) estimated in terms of % inhibition

of DPPH showed slight initial increase followed by gradual decrease under

all illuminations except in dark. Treatment means showed T6 maintained

maximum activity followed by T3, T4 and T5 while T2 showed minimum

RSA activity followed by T1. Storage interval means showed maximum

activity till 2nd week and than steadily declined till the end. The RSA

activities at the start and end of trial was found statistically (α-0.05) similar.

Interaction between treatments and storage intervals was initially found less

significant and than become highly significantly by the end of storage

period. The maximum activity was expressed in T3 and T6 during 3rd and 2nd

week storages respectively (Fig. 29).

In general RSA activity exhibited initial increase till mid storage

period and finally declined forming a sort of parabolic curve. However the

rate of increase and decrease in activity was considerably affected by

different illuminations. Radical scavenging activity increased during first

week and attained maximum by second week in T1 (45.43%), T2 (45.80%)

and T5 (47.57%) followed by progressive decline afterward. The trend

remained same at variable pace in T3 (48.73%), T4 (47.33%) and T5

(49.47%) where they showed maximum activity by the end of 3rd week

followed by steady decline. It is eventually observed that except in potato

tubers in dark storage all other placed under different illuminations lost

considerable activity below or close to their initial rate expressed before the

start of trial.

155

25

30

35

40

45

50

55

1 3 6 9 12 15 18 21 24 27


RSA

(%

)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 29 Radical scavenging activity in potato under different light sources showing highest activity in dark during storage (LSD (0.05) for treatment = 0.2980 LSD (0.05) for interval = 0.3854 LSD (0.05) for interaction = 0.9440)


156

RSA activity corresponds to the antioxidant potential retained by the

potato tubers and is associated with the presence of different functional

components like phenolic compounds, carotenoids, ascorbic acid and

tocopherols (Shahidi, 2002). In the present study storage under different

illuminations conferred diverse affects on these antioxidant components as

attributed to the parallel accumulation of phenolics and depletion of ascorbic

acids. The prolonged exposure of potato tubers to high energy illuminations

might bestow tuber stress consequently resulted in the loss of phenolic

substrate due to increased polyphenol oxidase activity (Bryant, 2004). The

significant retention of RSA activity at the end of storage under dark as

compare to different illuminations might be due to the appreciable retention

of dietary antioxidant like ascorbic acid, phenolics etc. The significant

correlation between RSA activity and these functional components has also

been reported by Hejtmankova, et al. (2009), Lachmann et al. (2008) and Kalt et

al. (2001).

4.3.12 Effect on Chips Moisture Contents

Increase in Chips moisture contents (CMC) was observed under all

illuminations including the dark storage. The treatment means showed non

significant difference between T1, T2, T5 and T3, T4, T6, however significant

difference exhibited between all the storage interval means. The interaction

between treatment and storage intervals was found significant with

maximum and minimum CMC recorded during the end and start of the

storage respectively (Fig. 30).

157

1.2

1.25

1.3

1.35

1.4

1.45

1.5

1 7 14 21 28


Chip

moi

sture

con

tents

(%

)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 30 Chip moisture contents in potato under different light sources showing lowest in dark during storage (LSD (0.05) for treatment = 0.00730 LSD (0.05) for interval = 0.00666 LSD (0.05) for interaction = 0.01633)


158

Maximum CMC was recorded in potato stored under red (1.44%)

light followed by fluorescent (1.43%) and blue (1.42%) illuminations at the

end of storage. The increase in CMC during these treatments remained

statistically similar through out their storage interval. Minimum CMC was

estimated in dark (1.37%) followed by green (1.38%) and mercury (1.40%)

illuminations. The increase in CMC amongst these treatments remained

statistically at par during most of the storage time.

The response of different illuminations on CMC segregated into two

distinct groups having non significant difference recorded between their

treatment means. 1st group exposed to high energy lights maintained

relatively high CMC included potato exposed to blue, fluorescent and red

illuminations while the 2nd group with relatively low CMC retained potato

stored in green, mercury and dark storage. CMC in different potato chips

remained unaffected by different illuminations within the group. The

exposure of tubers under high energy lights might cause tuber stress

followed by starch degradation consequently produced potato chips with

high moisture contents (Aguilera et al. 2000) as compare to those stored under

low energy illuminations and dark storage. Potato stored under dark retained

appreciable specific gravity contents due to intact starch molecules thus produced

chips with low moisture contents. The results presented are in agreement with the

findings of Mehta and Swinburn (2001) and pinthus et al. (1995) who reported

low CMC in potato chips processed from tubers with low specific gravity and

starch contents.

159


Chip fat absorption (CFA) increased with the advancement in storage

period under different illuminations and dark. Treatment means demonstrated

maximum CFA in T2 with non significant difference recorded with T5. T6

retained minimum CFA however found statistically at par with T1, T3 and T4. The

storage interval means showed highest CFA during the end of storage period

while lowest was estimated at the start of storage. The interaction between

storage intervals and treatment means showed maximum CFA at the end of

storage in T2 with non significant difference recorded amongst all other

treatments (Fig. 31).

CFA increased in all the treatments during storage period and found

maximum in potato placed under fluorescent light (33.10%) and minimum in dark

(30.87%) storage. The data showed no significant effect on CFA in response to all

other illuminations at the end of trial. Our results showed low fat absorption in

potato with high starch contents during storage under different illuminations. Such

inverse relationship confirmed the previous findings reported by Kita (2002),

Mehta and Swinburn (2001) and Hagenimana et al. (1998).


Chip Color (CCL) estimated in terms of approximate L- value showed

steady decrease with the increase in storage time under different illuminations. The

treatments means illustrated minimum CCL value in T2 and T5 while non

significant difference was recorded between T1 and T4. Maximum CCL values

were recorded in T6 and T3 which were found at par

160

29.5

30.3

31.1

31.9

32.7

33.5

1 7 14 21 28


Chip

fat

abso

rption

(%

)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 31 Chip fat absorption in potato under different light sources showing lowest value in dark during storage (LSD (0.05) for treatment = 0.2310 LSD (0.05) for interval = 0.2108 LSD (0.05) for interaction = 0.5165)


161

statistically (α-0.05). Storage interval means showed maximum CCL values by the

mid of storage time while minimum was recorded at the end of storage. The

interaction between treatments and storage intervals showed maximum CCL value

during the most of storage period however maximum CCL values were estimated

in T6 and T3 at the end of storage (Fig. 32).

Potatoes placed under dark retained appreciable CCL value during the

storage as compare to those placed under different illuminations. Maximum CCL

value (64.00) was identified in potatoes placed under dark however remained

statistically similar to those placed under green light while minimum CCL value

(59.33) was estimated in fluorescent illumination.

Chip Color is the most important quality parameter sternly related to the

consumer insight for the product acceptance (Segnini et al., 1999) and considered

as an important index of toxic acrylamide formation in potato during high

temperature processing (Stadler et al., 2002). Chip color is affected by chlorophyll

development and sugar accumulation during different illuminations. Since the

frying temperature and duration remained constant factors in during processing the

appearance of chlorophyll and advent of reducing sugars being the major

determinant of CCL values in the present trial. Potato with low reducing sugar

contents retained maximum CCL value as happened in those stored under dark.

The correlation between reducing sugar contents and potato chip color has also

been reported by different researchers like De Wilde et al. (2004) and Rodrigues-

Saona and Wrolstad, (1997).

162

58

60

62

64

66

1 7 14 21 28


Chip

col

or (L

-val

ue)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 32 Chip color in potato under different light sources showing highest value in dark and green light during storage (LSD (0.05) for treatment = 0.9399 LSD (0.05) for interval = 0.8580 LSD (0.05) for interaction = 2.1020)


163


Chip crispiness (CCR) scores showed a steady increase followed by final

decrease in all the treatments however the rate of decrease in CCR scores was

found maximum in potato exposed to fluorescent packaging and minimum under

dark storage. Treatment means revealed non significant difference between T3, T4

and T6, while T1, T2 and T5 were also found statistically similar at 5% level of

significance. Storage interval means showed initial increase in CCR scores which

remained maximal at the mid storage followed by decline in all treatments. The

interaction between treatments and storage intervals showed maximum CCR scores

in all treatments with non significant difference between them at mid storage

period. The interaction remained non significant with in most of the storage

intervals during the trial (Fig. 33). CCR scores expressed in T6 at the end of

storage were found similar to those identified on 3rd day storage in T1. Over all

percentage decline in CCR scores after attaining terminal value was found

maximum (16.7%) in T2 and minimum (8.7%) in potatoes under dark storage.

Crispiness in potato chips is dependent on the quality of raw material and

improved processing techniques. Potato tubers with high specific gravity and dry

matter contents reported to produce potato chips with high crispiness value

predominantly influenced by starch and non starch polysaccharides (proto pectin)

contents (Kita, 2002). Jaswal, (1991) reported that the potato with high specific

gravity contain high molecular weight, stable and compact polysaccharides (starch,

pectin etc.) contents preventing their integrity thus contributing to their appreciable

textural configurations during frying. In the present study the potato tubers with

164

3.5

4

4.5

5

1 7 14 21 28Storage intervals (day)

Chip

cri

spin

ess

(sco

res)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 33 Chip crispiness in potato under different light sources showing highest scores in dark and green light during storage (LSD (0.05) for treatment = 0.1424 LSD (0.05) for interval = 0.1300 LSD (0.05) for interaction = 0.3184)

165

high specific gravity value maintained appreciable CCR scores in the fried

products. Although CCR scores with in different illuminations remained

statistically in significant however potatoes with high specific gravity value as

those placed under dark storage produced chips with appreciable CCR value as

compare to those placed under different high energy illuminations which

confirmed the findings reported by the researchers above.


Chips flavor (CFL) estimated as scores recorded by the judges showed an

initial increase and eventual decreasing trend in all the treatments during the

storage. The treatment means exhibited maximum CFL scores recorded in T6

followed by T3, while non significant difference was identified between T1 and T4.

Lowest CFL scores were estimated in T2 followed by T5. Storage interval means

showed maximum CFL during D3 and D4 which were found statistically similar

while minimum scores were expressed at the start of experiment. The interaction

between storage intervals and treatments was significant with minimum CFL

estimated during 1st week storage and maximum estimated in T6 at mid storage

onwards till the end of storage (Fig. 34). In general CFL scores increased initially

under different illuminations followed by decline which was found highly

significant under fluorescent light. Steady decline in CFL scores observed in

potatoes stored under green and mercury illuminations. Over all dark potato

storage retained substantial CFL scores through out the storage period. Flavor

evolution in potato chips is primarily attributed to the oil uptake and corresponding

volatile formations during thermal processing (Warner et al., 1997).

166

3

3.5

4

4.5

5

1 7 14 21 28


Chip

fla

vor

(sco

res)

Blue

Florescent

Green

Mercury

Red

Dark

Fig. 34 Chip flavor in potato under different light sources showing highest scores in dark and green light during storage (LSD (0.05) for treatment = 0.1649 LSD (0.05) for interval = 0.1506 LSD (0.05) for interaction = 0.3688)


167

In the present study generally CFL scores were found in consistent with the other

sensorial attributes in potato chips. The maximum CFL scores were identified in

dark storage potatoes as compare to those placed under different illuminations.

Lowest flavor scores in potato placed under fluorescent illumination might be due

to the bitter taste conferred by elevated glycoalkaloids contents produced during

storage which has also been previously reported by Mensinga et al. (2005).

4.4 EFFECT OF DIFFERENT TEMPERATURE STORAGE ON THE


Potatoes are usually stored under low temperature for sprout prevention and

to ensure their continuous supply when ever needed. In the third experiment of 2nd

phase of study, post harvest storage stability of potato variety “Lady Rosetta” were

studied under different temperature regimes. The tubers were placed under 5oC,

15oC and 25oC temperatures storage and physico-chemical, functional and

processing attributes were studied at fourteen days interval.

4.4.1 Effect on weight Loss (%)

General trend was increase in weight loss (%) under all temperatures

storage; however the rate of increase was slower in T1 as compare to T2 and T3.

Treatment means showed significant difference between them with maximum

weight loss (%) estimated in T3 and minimum in T1. Data on weight loss revealed

significant differences between all the storage means with highest recorded on 84rth

day. Significant interaction was observed between treatments and storage intervals

with maximum weight loss (%) estimated in T3 after two month storage (Fig. 35).

168

0

3

6

9

12

15

1 14 28 42 56 70 84 98 112 126


Wei

ght lo

ss (%

)

5°C

15°C

25°C

Fig. 35 Weight loss in potato under comparative temperature storage showing minimum loss at 5oC (LSD (0.05) for treatment = 0.06734 LSD (0.05) for days interval = 0.12290 LSD (0.05) for interaction = 0.2129)


169

Amongst all temperature storage weight loss (%) increased with storage

period however remained under desirable limit during 1st month. Storage under

5oC and 15 oC expressed minimum weight loss (%) with non significant difference

recorded between them till 42nd day storage. Considerable weight loss (%) was

estimated at 25 oC on 42nd day storage which was similar to that recorded at 15 oC

on 112th day storage. Minimum weight loss estimated in T1 (3.25%) followed by T2

(8.29%) and T3 (13.29%) at their respective ends on 126th, 126th and 84rth days

storage. Overall highest weight loss (%) estimated in 25oC and not recorded after

84rth day storage due to shriveling and excessive sprouting rendering tuber

commercially unacceptable for the industrial processing.

Low temperature storage is an important technique in maintaining post

harvest quality of horticultural commodities however, it is essential to maintain

intact quality parameters and prevent them from low temperature disorders like

cold sweetening, chilling injury etc. Low temperature storage prevent sprouting in

potato by prolonging natural dormancy through imposed dormancy however the

critical temperature must be identified to prevent low temperature sweetening.

Weight loss (%) during post harvest storage of potato is attributed to moisture loss

due to evapotranspiration and dry matter loss due to respiration and sprouting

(Tester et al., 2005). Raghami (2009) reported direct relationship between storage

temperature and weight loss (%) in potato tubers. Ghazavi and Houshmand (2010)

studied respiration rate and weight loss (%) at different storage temperatures (5oC,

10oC and 15oC). The result indicated that the respiration rate and weight loss (%)

was found minimum at 5oC than other two temperature regimes. Amongst different

temperature storage, minimum weight loss (%) estimated at 5oC due to reduced

170

respiration rate which confirmed the findings of the researchers reported above.

The decreased weight loss under low temperature storage has also been reported by

different researchers in other horticultural commodities like Potato (Kyriacou et

al., 2009), Tomato (Javanmardi and Kubota, 2006), Mango (Abbasi et al., 2011),

Citrus (Mahajan, 2005) and Cherries (Martinez-Romero, et al. (2008).


Total soluble solid (TSS) in potato exhibited general increase during the

storage period with highly prominent elevation observed in T1. Treatment means

showed significant difference between them with maximum TSS estimated in T1

followed by T2 and T3. Storage interval means showed significant difference with

highest TSS retention recorded at the end of storage period with non significant

difference recorded between 70th, 98th and 112th days. The interaction between

treatments and storage intervals was highly significant with maximum TSS

estimated in T1 during most of the storage period (Fig. 36).

Storage at 5oC retained maximum TSS retention during most of the storage

period. TSS remained highest (6.90 oBrix) till 42nd day storage followed by steady

decline afterward. TSS accumulation remained steady at 25oC with final decline

(6.42 oBrix) observed on 84rth day storage. Storage at 15oC showed continuous

accumulation of TSS through out the storage period with maximum contents (6.55

oBrix) estimated on 126th day storage. Nevertheless TSS contents remained

considerably high in T1 than all other treatments with maximum percentage

increase recorded on 28th day (16.9%) followed by T3 on 70th day (13.42%) and T2

on 126th day (12.36%) storage.

171

5.5

5.9

6.3

6.7

7.1

1 14 28 42 56 70 84 98 112 126


Tot

al s

olub

le s

olid

s (o

Bri

x)

5°C

15°C

25°C

Fig. 36 Total soluble solids in potato under comparative temperature storage showing maximum increase at 5oC (LSD (0.05) for treatment = 0.00517 LSD (0.05) for days interval = 0.00943 LSD (0.05) for interaction = 0.01633)


172

TSS accumulation in potato under storage is associated with the hydrolytic

conversion of starch into soluble sugars (Kittur et al., 2001). The phenomenon is

highly desirable in most of the climacteric fruits and considered as ripening index.

Contrary to this the same is not required in potato due to poor processing

performance in frying. Interestingly potato crop exhibit increased total soluble

solids accumulation at diverse temperature regimes due to starch degradation

because of high respiration rate as well as cold sweetening below some critical

temperature. Thus the optimum storage temperature for particular potato variety is

very important for prolong storage. In the present study different temperature

levels showed variable response regarding their total soluble solids accumulation.

The significant TSS increase in T1 (5oC) might be due to rapid conversion of starch

into soluble sugars (Endo et al., 2006) primarily the sucrose which afterward

hydrolyzed into glucose and fructose due to activities of enzyme invertase. Steady

decline afterward might be due to the substrate oxidation during tuber respiration,

the similar findings have also been reported by Sonnewald, (2001). Storage under

other two temperature regimes showed steady increase in TSS due to slower starch

hydrolysis; however final decline observed in T3 might be due to increased

sprouting lead to oxidation of soluble sugars as respiratory substrate (Sowokinose,

1990).


Glucose contents showed variable trend under different temperature storage

with prominent initial increase followed by steady decline in T1, steady increase in

T2 and steady increase with final decline in T3 during storage. Treatment means

revealed maximum glucose retention in T1 followed by T2 and T3. Storage interval

means exhibited significant difference between them with statistically similar

glucose contents found on 98th and 126th days (α-0.05). Interaction between storage

173

intervals and treatments was highly significant and showed maximum glucose

retention in T1 during most of the storage period (Fig. 37).

Storage of potato under 5oC temperature showed highly significant increase

in glucose contents as compare to other temperature regimes. This rise was

paramount and remained at highest value (842.11 mg/100g) by 1st month storage

followed by steady decline however remained more than 2-folds than other two

treatments during rest of the storage period. Steady increase in glucose contents

witnessed both under 15oC and 25oC temperatures storage and evolved within

close range but the rate of increase was found swifter in later than former. At 15oC

the maximum glucose contents (325.63 mg/100g) were estimated on 126th day

storage which was close to that identified in 25oC on 84rth day storage.

Potato storage under low temperature is carried out in order to prevent

potato sprouting through imposed dormancy (Wiltshire and Cobb, 1996). The

storage temperature is however associated with reducing sugar accumulation

predominantly present in the form of glucose and fructose, negatively correlated to

the fry color (Hermen et al., 1996) and also reported to be major precursor in toxic

acrylamide formation during processing (Amrein at al., 2004). Knowles et al.

(2009) studied the reducing sugar contents in different potato cultivars under low

temperature and found maximum during 1st month followed by gradual decline

showing partial acclimation. Rapid increase in reducing sugars under low

temperature storage was also reported by other researchers like Blenkinsop et al.

(2002), Chuda et al., (2003), Nourian et al. (2003) and Tamaki et al. (2003). Our

results regarding glucose contents showed that the influence of storage time was

less pronounced than the effect of storage temperature. Significant increase in

glucose contents at 5oC temperature confirmed the previously reported findings.

Steady increase in the glucose contents at temperature regimes i.e. 15oC and 25oC

174

0

150

300

450

600

750

900

1 14 28 42 56 70 84 98 112 126


Glu

cose

(m

g/10

0g)

5°C

15°C

25°C

Fig. 37 Glucose in potato under comparative temperature storage showing maximum contents at 5oC (LSD (0.05) for treatment = 1.158 LSD (0.05) for days interval = 2.114 LSD (0.05) for interaction = 3.662)


175

might be attributed to the effect of storage time being less significant as compare to

storage temperature. The presence of moderate glucose contents at intermediate

temperature (15oC, 25oC) confirmed the findings reported by other researchers like

Kyriacou et al. (2009), Edwards et al. (2002) and Nourian et al. (2003) who

presented low sugar contents in potato above 10oC storage. Our results showed low

glucose accumulation at 15oC and 25oC however the postharvest storage life was

significantly higher in former (126 days) than later (84 days) temperature storage.

The ultimate decline in glucose contents at 25oC might be due to its utilization as

respiratory substrate during high respiration rate due to sprouting and tuber

senescence (Kyriacou et al., 2008).


Total sugars accumulation in response to different storage temperature was

consistent with that found for glucose contents. Generally total sugars increased in

all treatments followed by steady decline with highly significant rise estimated in

T1. Treatment means established significant difference between stored potato with

maximum and minimum sugar contents identified in T1 and T3 respectively.

Storage interval means demonstrated significant difference between them with

maximum sugar retention after three month storage. The interaction between

treatment means and storage intervals was found significant with maximum values

estimated in T1 during most of the storage period (Fig. 38).

Amongst all temperature levels maximum sugar contents were estimated in

5oC with dominant increase (< 3%) during 1st month storage and retained elevated

sugar contents in tubers till 56th day storage there after followed by steady decline

176

500

1000

1500

2000

2500

3000

3500

1 14 28 42 56 70 84 98 112 126


Tot

al s

ugar

s (m

g/10

0g)

5°C

15°C

25°C

Fig. 38 Total sugar in potato under comparative temperature storage showing maximum contents at 5oC (LSD (0.05) for treatment = 3.762 LSD (0.05) for days interval = 6.86 LSD (0.05) for interaction = 11.90)


177

during rest of the storage period. Sugar contents increased steadily under other

two temperature regimes with their maximum contents identified in T2 and T3 at

126th and 70th day respectively.Total sugar contents produced in potato primarily in

the form of sucrose, glucose and fructose due to starch degradation (Hajirezaei et

al., 2003). These sugar contents are metabolized during tuber respiration along

with their contribution in maillard reaction for non enzymatic browning during

processing. Although sucrose does not directly participate in maillard reaction but

contributes to chip color development due to its hydrolysis during frying

(Leszkwiat et al., 1990). Endo et al. (2006) compared the sugar accumulation in

some potato varieties under different temperature regimes (2oC, 6oC, 8oC, 10oC,

and 18oC) and reported maximum sugar contents below 8oC temperature. Similar

observations were recorded by Kyriacou et al. (2009), Kazami et al. (2000) and

Herman et al. (1996) who estimated inverse relationship between total sugar

contents and temperature in potato tubers under storage. In the present

investigation maximum sugar contents estimated at 5oC temperature confirmed the

finding reported by above researchers. At low temperature storage decrease in total

sugars was comparatively higher than glucose contents which might be attributed

to synchronize glucose addition due to sucrose cleavage mediated through vacuolar

invertase activity which also confirmed the findings by Junker et al. (2006).


Changes in starch contents under different temperature storage revealed

general decrease with the progress in storage period. Data related to treatment

means showed significant different between them with maximum and minimum

178

starch accumulation estimated in T2 and T3 respectively. Storage interval means

articulated significant difference between them with highest and lowest starch

contents estimated on 1st and 112th days respectively. Interaction between storage

interval and treatment means was highly significant with maximum starch contents

estimated in all treatments at the start of storage while lowest starch contents were

recorded in T1 at the end of storage (Fig. 39).

In general starch contents declined under all temperatures storage however

express percentage decline was recorded at 5oC and remained significantly lower

till the end of storage period (32.0%). Storage at 15oC retained appreciable starch

contents till 84rth day storage and reduction estimated was only 7.1% as compare to

29.5% and 21.5% decrease recorded in T1 and T3 respectively. Over all percentage

declines recorded at 15oC (16.1%) and 25oC (21.5%) till 126th and 84rth day storage

respectively. Contrary to other treatments, storage at 25oC presented minor initial

increase in starch contents there after followed by gradual decline. Storage at

ambient temperature (25oC) retained higher starch contents than 5oC and lower

than 15oC but the commercial storage life remained only up to 12 weeks as

compare to 18 weeks storage found at other two temperatures.

Starch is the predominant carbohydrate present in potato contributing 70-

80% of total dry matter contents and proportional to its specific gravity value

(Kazami et al., 2000). Starch contents have been observed to change during post

harvest storage and in turn affect the processing attributes of potato (Herman et al.,

1996). Starch and sugars are the principal chemical components in potato tubers

influenced by low temperature storage mediated through specific enzymes.

179

13

14

15

16

17

18

19

20

1 14 28 42 56 70 84 98 112 126


Sta

rch (

%)

5°C

15°C

25°C

Fig. 39 Starch in potato under comparative temperature storage maintaining maximum contents at 15oC (LSD (0.05) for treatment = 0.0400 LSD (0.05) for days interval = 0.0730 LSD (0.05) for interaction = 0.1265)


180

Nourian et al., (2003) studied the quality changes in potato at different

storage temperatures and found that starch contents decreased with the decrease in

storage temperature and increase in storage time. Similar observations proposed by

Rivero et al. (2003) who reported progressive decrease in starch and concurrent

increase in sugar contents with the increase in storage period. Low temperature

storage cause significant degradation of starch polymers into soluble sucrose due to

inactivation of glycolytic enzymes like Phosphofructokinase and fructose -6-

phosphate. Sucrose hydrolysis is mediated through enzyme invertase ultimately

results in the increase in reducing sugars like glucose and fructose (Sonnewald,

2001). The energy requirement of dormant potato tuber during post harvest storage

largely dependent on it starch contents.

Our results presented significant decline in starch contents both under low

temperature storage (5oC) and extension in storage period (126 days). However the

prominent decline under low temperature storage showed that the reduction in

starch content is largely a function of storage temperature than the storage time.

Significant decrease in starch contents at 25oC after two month storage till the end

(84 days) might be due to the sufficient energy required by the growing sprouts as

also been observed by Farre et al. (2001). Storage of potato tubers at intermediate

storage temperature (15oC) retained appreciable starch contents and extended the

storage life up to 126 days however associated with increase weight loss as

compare to low temperature storage (5oC). The results framed in the present study

confirmed the findings of previous researchers like Karim et al. (2008), Kumar et

al. (2004), Nourian et al. (2003) and Neilson et al. (1997).

181

4.4.6 Effect on Ascorbic acid

General trend was decrease in ascorbic acid (AA) contents in all treatments

however the retention of ascorbic acid was inversely proportional to the storage

temperature. Treatment means showed significant difference between them with

maximum AA contents in T1 followed by T2 and T3. Storage interval means

showed significant difference between them with minimum AA contents estimated

at the end of storage. Significant interaction between treatments and storage

intervals was observed with maximum AA estimated at start of storage while

minimum contents estimated in T2 and T3 at the end of their respective storage

period (Fig. 40).

Amongst different temperature studied storage of potato tubers at 5oC

presented lowest reduction in AA till 126 days storage. Percentage reduction in

ascorbic acid contents was 30.2%, 42.2% and 42% at 5oC, 15oC and 25oC

respectively till the end of their respective storage periods. AA contents estimated

at 5oC at the end of storage i.e. 126th day (17.45 mg/100g) was higher than that

quantified on 56th day (16.09 mg/100g) storage at 25oC temperature. Moderate

reduction in AA contents has been observed at 15oC with lowest value estimated

on 126th day storage which was similar to that recorded at 25oC on 84rth day

storage.

Ascorbic acid is one of the most important quality parameter in fruits and

vegetables and is attributed to significant functional importance in human

metabolism. Retention of AA contents in horticultural crops during post harvest

storage largely influenced by different factors like genotype, agronomic practices,

growing conditions, maturity, harvesting techniques and post harvest management

(Lee and Kader, 2000). The loss of ascorbic acid is however primarily associated

182

14

16

18

20

22

24

26

1 14 28 42 56 70 84 98 112 126

Storage Intervals (Days)

Asc

orbic

aci

d (m

g/10

0g)

5°C

15°C

25°C

Fig. 40 Ascorbic acid in potato under comparative temperature storage maintaining maximum retention at 5oC (LSD (0.05) for treatment = 0.08001 LSD (0.05) for days interval = 0.1461 LSD (0.05) for interaction = 0.2530)


183

with inappropriate post harvest management of horticultural commodities.

Ascorbic acid is readily oxidized into dehydro-ascorbic acid in the presence of

molecular oxygen mediated through enzyme ascorbate oxidase (Saari et al., 1995).

Amongst different post harvest management techniques temperature management

is one of the key factor in AA retention under storage. The considerable retention

of this valuable antioxidant can be secured by apt selection of storage temperatures

and storage times. Nourian et al. (2003) studied the changes in ascorbic acid

contents under different temperature regimes and stated that the ascorbic acid

contents decreased with the increase in storage temperature and storage duration.

Similar results were reported by Blenkinsop et al. (2002) regarding decline in

ascorbic acid with the progression in storage time. The present investigation

revealed that the retention of AA contents in potato during their post harvest

storage is equally associated with their storage temperature and storage time. The

eventual decline in ascorbic acid at 5oC might be due to their degeneration under

prolonged storage as also reported by Davies et al. (2002). Lowest retention of AA

contents at 25oC as compare to other two temperature regimes (5oC, 15oC) and

significant decline in AA contents with the progression in storage time confirmed

the findings of the researchers reported above and also found in line with the

findings of other scientists like Tamaki et al. (2003), Rivero et al. (2003) and

Vorne et al. (2002).


In response to different temperature storage chlorophyll contents continue

to increase significantly with the progression in storage period. Treatments means

demonstrated maximum chlorophyll accumulation in T3 followed by T2 and T1.

Storage interval means showed significant difference in their chlorophyll contents

184

with non significant difference recorded between 1st and 14th days. The interaction

between treatments and storage intervals was found highly significant with

minimum contents estimated till second week storage in all treatments and

maximum recorded in T3 at the end of storage period (Fig. 41).

Chlorophyll contents continued to increase with the increase in storage

period however the increase was prominent at 25oC than other two temperature

regimes. The percentage increase in chlorophyll content at 25oC was around 3-

folds (1.83 mg/100g) till 84rth day afterward expired due to excessive weight loss

and sprouting. Storage of tubers at 5oC and 15oC temperatures showed minor

increase in Chlorophyll contents till 42nd day afterward substantial increase (1.70

mg/100g) witnessed at 15oC till 126th day storage. Lowest overall chlorophyll

contents were estimated in storage at 5oC with percentage increase remained less

than 2-folds (1.15 mg/100g) till the end of 126th day storage.

Increase in chlorophyll contents reported to alter the brightness in potato

tubers and the phenomenon is primarily associated with exposure to different

illuminations and temperature (Grunenfelder et al., 2006). Edward and Cobb,

(1997) studied the effect of different temperature levels (5oC, 10oC, 20oC, 25oC) on

chlorophyll accumulation in potato and observed maximum and minimum

accretion at 25oC and 5oC respectively. Increase in chlorophyll contents also

noticed under different temperature regimes in the present study and presented

considerable alteration in tuber color. Our results showed considerable increase in

chlorophyll contents with increase in storage temperature and storage duration.

Magnitude of chlorophyll accumulation increased with the

185

0.5

0.9

1.3

1.7

2.1

1 14 28 42 56 70 84 98 112 126


Chl

orop

hyll (m

g/10

0g d

.w)

5°C

15°C

25°C

Fig. 41 Chlorophyll in potato under comparative temperature storage maintaining maximum contents at 25oC (LSD (0.05) for treatment = 0.02829 LSD (0.05) for days interval = 0.05165 LSD (0.05) for interaction = 0.08946)


186

increase in storage temperature. The chlorophyll contents estimated at 25oC on 56th

day was higher than that identified at 5oC on 126th day storage. Over all results

showed that both storage temperature and storage durations were equally

associated with the increase in chlorophyll contents. These results are also found in

close agreement with the findings of Nourian et al. (2003).


Total Glycoalkaloids (TGA) accrual in terms of solanine equivalent showed

an increasing trend with the progression in storage period under all temperature

storages (Fig. 42). Treatment means showed significant difference between them

with maximum TGA contents estimated in T3 and minimum in T1. Most of the

storage interval means were found significantly different with non significant

difference identified in 56th and 112th days, 70th and 126th days. The interaction

between storage intervals and treatments was found less significant till 28th day

afterward exhibited maximum TGA accumulation in T3 at the end of storage

period (Fig. 42).

Storage of potato tubers under all temperature regimes showed increase in

TGA contents with the increase in storage time. Similar TGA contents had been

observed under all temperatures till 1st month storage there after more than 12-

folds increase estimated at 25oC till the end of storage. Moderate TGA contents

had been recorded at 15oC with around 7-folds increase till 126th day storage. In

comparison TGA contents quantified at 15oC on 126th day was less than that

estimated at 25oC on 84rth day storage. Storage at 5oC accumulated lowest TGA

contents till 126th day storage and remained around 5-folds increase till the end.

187

0

15

30

45

60

75

90

1 14 28 42 56 70 84 98 112 126


TG

A (m

g/10

0g d

.w)

5°C

15°C

25°C

Fig. 42 Total Glycoalkaloids in potato under comparative temperature storage showing lowest contents at 5oC (LSD (0.05) for treatments = 0.810 LSD (0.05) for days interval = 1.479 LSD (0.05) for interaction = 2.561)


188

Nevertheless except in T3 at the end of storage the TGA increase remained under

safe human intake limit i.e. 20mg/100g f.w as suggested by Mensinga et al.,

(2005).

Sengul et al. (2004) concluded that mechanical damage, light and high

temperature is major environmental stress factors prompt TGA synthesis in potato

tubers during their post harvest storage. In the present study maximum TGA

accumulation at 25oC as compare to other storage temperatures confirmed the

above reported findings. Contradictory observations were proposed by Rita et al.

(2007) who found higher TGA accumulation in potato tubers at refrigerated

temperature than those placed under room temperature however he related the

varietal specific biosynthesis of TGA which might not be the case as in the present

study. Significant increase in TGA contents in response to elevated temperature

was reported by other researchers like Nema et al. (2008), Sengul et al. (2004) and

Rosenfeld et al. (1995)


Storage of potato tubers under all temperature regimes showed general

parabolic trend with initial unparallel increase in Total Phenolic Contents

(TPC) followed by gradual inconsistent decline till the end. Treatment means

showed significant difference between them with maximum TPC estimated in

T1 and minimum in T3. Storage interval means revealed significant difference

between them with lowest TPC estimated at the start and end of the storage.

Significant interaction was observed between treatments and storage intervals

with maximum TPC contents estimated in T1 and T2 on 70th and 56th days

respectively (Fig. 43).

189

75

100

125

150

175

1 14 28 42 56 70 84 98 112 126


TP

C (

mg/

100g

d.w

)

5°C

15°C

25°C

Fig. 43 Total phenolic contents in potato under comparative temperature storage showing maximum retention at 5oC

(LSD (0.05) for treatment = 1.253 LSD (0.05) for days interval = 2.030 LSD (0.05) for interaction = 3.751)


190

TPC increased in all treatments with the increase in storage duration

however 5oC retained appreciable contents as compare to other temperature

storages. Storage of potato tubers at 25oC showed initial increase in TPC till

1st month storage subsequently followed by extensive decline (80.52

mgGAE/100g) till 84rth day and not determined afterward due to loss of their

commercial significance. TPC increased continuously at 15oC till 70th day

thereafter presented considerable decline (121.70 mgGAE/100g) by the end

of storage period. Increase in TPC at 5oC also exhibited gradual increase

with no sign of cessation till the end of storage period (159.50

mgGAE/100g).

Total phenolic contents are the secondary metabolites present in

potato known to carry anti oxidant, anti cholesterol and anti malignant

properties (Andre et al., 2009). Potato are considered as one of the best

source of these polyphenolic compounds with contents varying between

170mg/Kg to 19mg/kg in peeled and cooked potato respectively (Mattila and

Hellstrom, 2007). TPC in potato are reported to influenced by different

intrinsic factors like color, variety (Lachman et al., 2008) as well as extrinsic

factor like growing locality, fertilization, post harvest storage conditions

(Hamouz et al., 2006). TPC accumulation in the potato and other plants is

attributed to their defence mechanism against different mechanical stress;

bruising, mechanical injuries conferred by unfavorable growing conditions,

in appropriate post harvest handlings, insects/pest infestations etc (Friedman,

1997). Temperature management during post harvest storage of potato is

widely approved technique to prolong the storage life by preventing water

loss and sprouting. Barberan and Espin, (2001) studied phenolic compounds

191

as quality determinant in different fruits and vegetable and reported their

appreciable retention at low temperature during post harvest storage. The

accumulation of phenolic contents in sweet potato in response to low

temperature storage has also been observed by Padda and Picha (2008). Vitti

et al. (2011) also observed increased phenolic contents in minimally

processed potato under 5oC and 15oC temperature storage. Significant

decline in TPC at 25oC after 2 month storage might be due to the tuber

closer to sprouting (Saltveit, 2000) consequently triggered rapid polyphenol

oxidase activities which lead to the decline in total phenolic contents.

Storage at intermediate (15oC) and low temperature (5oC) storages after an

initial increase (Madiwale et al., 2011) retained appreciable TPC contents

till the end which might be associated with their low PPO activities. The

results reported in the present study are also in line with the findings of other

researchers like Lachman et al. (2008) and Gonzalez et al. (2004).


In general influence of different temperatures on radical scavenging

activity (RSA) (anti oxidant activity determined in terms of % inhibition of

DPPH) showed initial increase followed by gradual decrease with the

progression in storage period. The ultimate decline in RSA was lowest in T1

as compare to other two temperature storages. Treatment means

demonstrated maximum activity in T1 followed by T2 and T3. Storage

interval means illustrated maximum activities after 1st month storage while

minimum RSA estimated at the start and end of storage period. Interaction

between treatment and storage interval during the trial was found

192

20

25

30

35

40

45

50

1 14 28 42 56 70 84 98 112 126


RSA

(%

)

5°C

15°C

25°C

Fig. 44 Radical scavenging activity in potato under comparative temperature storage showing highest activity at 5oC (LSD (0.05) for treatment = 0.362 LSD (0.05) for days interval = 0.642 LSD (0.05) for interaction = 1.113)


193

highly significant with highest activities recorded in T1 and T2 on 70th and

56th days respectively (Fig. 44).

Significant increase in Radical scavenging activity witnessed in all

treatments till 1st month afterward declined at 25oC while continued to

increase at 5oC and 15oC till 70th day storage. Storage at 25oC showed

highest decline (23.00%) till 84rth day thereafter not estimated due to loss of

commercial viability in potato tubers. Closely similar RSA values were

estimated at 5oC and 15oC on 70th day however the later showed

considerable decline (28.23%) till the end of storage period. Storage at 5oC

showed gradual increase in RSA till 70th day however unlike other

treatments retained appreciable activity on 126th day (41.50%).

Oxidative stress conferred by free radicals considered as major factor

in various degenerative disorders and are capable of damaging essential

biomolecules (Haila, 1999). Anti oxidants are the substances reported to

prevent these bio molecules either by delaying cellular oxidable substrates or

by quenching the free radicals produced in the biological system

(Hejtmankova et al., 2009). Potato considered as substantial source of these

antioxidant compounds mostly present as ascorbic acids, polyphenols and

anthocyanins depending upon the type and color of potato varieties

(Lachman et al., 2008). The increase in RSA during storage expressed

consistent pattern with the total phenolic contents with some deviations.

Madiwale et al. (2011) and Blessington et al. (2007) reported increase in

antioxidant activity during the storage period which also reported in the

present study. Appropriate temperature management in potato storage

194

reported to enhance anti oxidant activity with stumpy post harvest losses.

Lewis et al. (1998) reported increase in phenolic and anthocyanin contents

consequently high anti oxidant activity in colored potato varieties under low

temperature storage. Similar results were reported by Christie et al. (1994)

who found increased phenol biosynthesis under low temperature storage

which confirmed the results reported in the present study. Significant decline

in RSA at 15oC and 25oC on 126th and 84rth day storage respectively might

be due to the loss of phenolic and ascorbic acid contents (reported in the

present study). Moderate decline in RSA activity was also observed at 5oC at

the end of storage which might only be due to the degeneration of ascorbic

acids under prolonged cold storage as also reported by Davies et al. (2002).


In general polyphenol oxidase (PPO) activity in potato tuber was found

proportional to their storage temperature. Treatment means showed significant

difference in their PPO activity with maximum estimated in T3 and minimum in

T1. Storage interval means illustrated maximum PPO activity on 84rth while

minimum at 14th days of storage. The interaction between treatments and storage

intervals was found significant with maximum activity recorded in T3 at the end

of storage period (Fig. 45).

Significant decrease in PPO activity observed at 5oC temperature which

remained below their initial value till the end of storage period. The highest

percentage decline (41.6%) was estimated on 70th day after ward minor increase

in PPO activity recorded till 126th day.

195

15

30

45

60

75

90

1 14 28 42 56 70 84 98 112 126


PPO

(U

/g d

.w)

5°C

15°C

25°C

Fig. 45 Polyphenol oxidase in potato under comparative temperature storage showing lowest enzymatic activity at 5oC (LSD (0.05) for treatment = 0.351 LSD (0.05) for days interval = 0.785 LSD (0.05) for interaction = 1.115)


196

PPO activity showed overall steady and comparatively swift increases in potato

stored at 15oC and 25oC respectively. Storage at 15oC showed minor decline

(2.5%) till 84rth day after ward illustrated percentage increase of 21.5% up to

126th day. Highly significant PPO activity estimated in potato stored at 25oC

during storage with maximum activity recorded was around 2.5 folds than the

initial value on 84rth day storage. Rapid increase in PPO activity was observed

after 1st month storage which persisted till the end.

Nourian et al., (2003) studied changes in quality attributes of potato

tubers stored under five different temperature regimes i.e 4oC, 8oC, 12oC, 16oC

and 20oC. He concluded that PPO activity in potato tuber is directly proportional

to their storage temperature. Amongst different temperatures studied he found

decrease and increase in PPO activity at 4oC and 20oC temperature respectively.

Similar results were also reported by Junior et al. (2002) who observed high PPO

activity in lettuce at 2oC than those placed at 10oC storage. Our results concluded

that amongst different temperature studied storage at 5oC efficiently retained low

PPO activity in turn improved storage stability of potato as compare to those

placed at intermediate (15oC) and ambient temperature (25oC) which confirmed

the above reported findings. Decrease in PPO activity at low temperature storage

in different potato cultivars has also been observed by other researchers like at

Moretti et al. (2002), Nunes et al. (2001), and Zorzella et al. (2003).


General trend regarding POD activity showed initial decrease followed by

eventual increase in T1 and T2 while continuous increase observed in T3 during

197

storage. Treatment means showed significant difference with maximum POD

activity recorded in T3 and minimum in T1. Storage interval means illustrated

steady increase in POD till fourth week followed by maximum activity estimated

on 84rth day. The interaction between treatments and storage interval was

significant with highest activity identified in T3 after 1st month storage (Fig. 46).

Storage of potato tubers at 5oC and 15oC revealed an initial increase

followed by final decrease at the end of 126th day. The decline in POD activity

was more pronounced (35.4%) at 5oC till 70th day afterward increased close to the

activity level estimated before the start of experiment. Storage of tubers at 15oC

also exhibited slight decrease in activity i.e. 9.6 U/100 g up to 56th day storage

there after increased up to 15.25 U/100 g on 126th day storage. Potato tubers

stored at 25oC attained significant increase in their POD activity through out the

storage period. The prominent increase in POD activity started after 1st month

storage and achieved more than 3-folds higher than the initial value on 84rth day.

POD and PPO are considered as the major enzymes in horticultural

commodities responsible for the quality loss due to phenolic dilapidation (Tomas-

Barberan and Espin, 2001) moreover in browning perspective synergistic effect

between these two enzymes have also been reported (Subramanian et al., 1999).

Aydin and Kadioglu, (2001) reported increased POD activity in fruits and

vegetables under stress conditions and with the progression in their physiological

stages i.e. senescence. Our results showed significant increase in POD activity

after 1st month onward till the onset of sprouting at 25oC which confirmed the

above reported observations.

198

5

15

25

35

45

1 14 28 42 56 70 84 98 112 126


PO

D (U

/100

g d.w

)

5°C

15°C

25°C

Fig. 46 Per oxidase in potato under comparative temperature storage showing lowest enzymatic activity at 5oC (LSD (0.05) for treatment = 0.1953 LSD (0.05) for days interval = 0.3566 LSD (0.05) for interaction = 0.6202)


199

Vitti et al. (2011) studied enzymatic activity in different potato varieties like

Agata, Asterix and Monalisa at 5oC and 15oC and reported low POD activity in

former than in later temperature storage in all the tested varieties. Similar

observations were recorded by Cantos et al. (2002) who reported decline in

enzyme activity at 5oC in spunta cultivar. The lowest estimated POD activity at

5oC followed by 15oC in the present study is in line with the findings of

researchers stated above.

4.4.13 Effect on Chip Moisture Content

In general chip moisture contents (CMC) increased in response to

different temperature however an eventual decline observed only in T1 at the end

of storage period. Treatment means illustrated maximum CMC in T1 and T3 with

non significant difference estimated between them. Storage interval means

exhibited maximum CMC during 84rth day followed by 70th days. Non significant

difference was observed between most of the storage intervals in their CMC. The

interaction between treatments and storage was significant with maximum CMC

estimated in T3 on 56th day till the end of storage period (Fig. 47). Statistical

analysis revealed non significant difference between potato tubers in their CMC

stored at 5oC and 25oC however difference between their ultimate storage

duration remained highly significant with 126th (D10) and 84rth (D7) day storage

respectively. CMC increased by around 1.6-folds at 5oC storage till 42nd day after

ward decreased progressively with over all 1.34-folds increase estimated at the

end of storage. Storage at 25oC showed moderate increase in their CMC till 42nd

day there after exhibited progressive 2.25-folds increase till the end of storage

period. Storage of the potato tubers at 15oC temperature maintained moderate

200

1

1.5

2

2.5

3

1 14 28 42 56 70 84 98 112 126


Chip

moi

stur

e co

nte

nts

(%

)

5°C

15°C

25°C

Fig. 47 Chip moisture content in potato under comparative temperature storage showing highest content at 25oC



201

increase in their CMC during most of storage period however ended with around

1.4-folds increase and found statistically similar to 5oC on 126th day storage.

Frying cause the removal of significant amount of water through potato

chip surface (Hubbard and Farkas, 1999) thus precisely termed as dehydration

process. The process is associated with significant reduction of moisture contents

in the processed products (chips, French fries etc) along with corresponding oil

uptake. Potato with high specific gravity and appreciable starch contents were

reported to produce potato chips with low moisture contents (Pinthus et al., 1995).

Kyriacou et al. (2009) evaluated processing potential of different potato varieties

under three temperature regimes (4.5oC, 8.5oC and 11oC). He concluded that the

starch degradation and sugar accumulation was inversely proportional to their

storage temperatures.

High initial CMC in potato stored at 5oC might be due to starch degradation

with concurrent accumulation of reducing sugars as also reported by the

researchers above. Storage at 15oC maintained appreciable starch contents with

intact cellular configuration thus presented steady increase in CMC till the end of

storage. CMC remained highest in potato stored at 25oC which might be the

function of storage duration rather than storage temperature. The increased CMC at

the end of storage is associated with significant starch degradation in potato close

to sprouting as also stated by Bielmelt et al. (2000). The significant correlation

between Chip moisture contents and starch contents has also previously reported

by researchers like Aguilera et al. (2000) and Kita et al. (2004).

202


Irrespective of different temperature storages chip fat absorption (CFA)

increased with the progression in storage period however the increase was highly

prominent in T1 and T3 during the start and end of storage respectively. Treatment

means established minimum CFA in T2 followed by T1 and T3. Storage interval

means showed minimum CFA in 1st day and maximum during 84rth and 70th days

which were found at par statistically. Interaction between storage intervals and

treatment means was significant with highest CFA recorded in T1 on 84rth day

(Fig. 48). Data pertaining to CFA was found in consistent with that observed in

CMC under different storage temperatures. Variable trend regarding CFA in

potato chips was observed under studied temperatures. At 25oC temperature CFA

remained slow till 42nd day storage trailed by progressive increase of around 1.5-

folds till 84rth day storage. In comparison the increase observed in last 28 days

was higher than that estimated during the initial 42 days storage. As discussed

before tubers stored at 25oC were discarded after ward due to loss of their

commercial significance. CFA remained steady during most of the time under

15oC storage with over all around 1.2 folds increase observed on 126th day

storage. Storage at 25oC tuber placed under 5oC temperature revealed initial

increase in their CFA till 42nd day followed by steady decline ti1l the end. In

addition the increase in CFA was lower and storage duration was found

significantly higher than the tuber stored at 25oC.

CFA is associated with the removal of moisture contents through cellular

matrix leaving behind capillary pores which were consequently filled by oil as

observed by Mellema, (2003). Some of the important factors reported to affect chip

fat absorption in potato chips during processing include tuber specific gravity

203

30

33

36

39

42

45

48

1 14 28 42 56 70 84 98 112 126


Chip

fat

abso

rpti

on (

%)

5°C

15°C

25°C

Fig. 48 Chip fat absorption in potato under comparative temperature storage showing highest value at 25oC (LSD (0.05) for treatment = 0.4494 LSD (0.05) for days interval = 0.8204 LSD (0.05) for interaction = 1.421)


204

(Mehta and Swinburn, 2001), modification in size and thickness (Gamble and

Rice, 1988), modification in frying techniques (Mehta and Swinburn, 2001).

Amongst potato with high specific gravity and intact starch contents are the most

crucial factor in ultimate chip fat absorption during processing. Nielsen et al.

(1997) observed enzyme mediated reduction in starch contents in different potato

varieties under low temperature storage which caused significant quality loss

during processing. Kita, (2002) observed inverse relationship between tuber starch

contents and chip fat absorption. Storage at 5oC and 25oC presented high CFA in

potato chips which might be associated with starch degradation due to the low

temperature sweetening (Karim et al., 2008) and sprouting (Bielmelt et al., 2000)

respectively. Low fat absorption in potato placed at 15oC as compare to other

storage temperatures might be due to the presence of high dry matter and intact

starch contents which verified the previously reported findings by Kita et al.

(2004), Tawfik et al. (2002) and Hagenimana et al. (1998).

4.4.15 Effect of Chip Color

Chip Color (CCL) estimated in terms of approximate L-value under

different temperature showed general decrease with the increase in storage time.

Treatments means showed lowest CCL value in T1 while highest CCL was

observed in T2. Storage interval means showed maximum and minimum CCL

values on 1st and 126th days respectively. The interaction between treatments and

storage intervals was significant with lowest CCL value estimated in T1 during the

1st half of storage duration (Fig. 49). Storage at 5oC presented maximum

percentage decrease (24.6%) on 28th day which continued at the same level as well

till56thdaystorage.

205

45

50

55

60

65

70

1 14 28 42 56 70 84 98 112 126


Chip

col

or (L

-val

ue)

5°C

15°C

25°C

Fig. 49 Chip color in potato under comparative temperature storage showing highest value at 15oC (LSD (0.05) for treatment = 1.121 LSD (0.05) for days interval = 1.625 LSD (0.05) for interaction= 3.545)


206

The CCL values subsequently followed gradual increase and ended with ultimate

20% decrease from the initial value. Storage at 25oC retained fine CCL values till

42nd day storage afterward exhibited 20% on 84rth day storage which was similar to

that estimated at 5oC on 126th day storage. Significant retention of CCL values

were estimated at 15oC during most of the storage period with lowest eventual

percentage decline (8.72%) reported on 126th day storage.

Chip Color (CCL) is the most important factor for consumer acceptance

and is primarily associated with the presence of their reducing sugar contents

(Tamaki et al., 2003). The increased reducing sugar contents in potato lead to the

non enzymatic browning during processing as a consequence of maillard reaction

hence reduce the product quality (Herman et al., 1996). Storage at 15oC and 25oC

temperature showed minor tendency of decline in CCL value over storage period

in contrast the decline was rapid at 5oC with in 1st month of storage. It was evident

from our results that reducing sugars sharply increased at 5oC with in 1st week and

corresponded with the significant decline in CCL values during the same period.

This inverse relationship between reducing sugars and CCL was also been cited by

different researchers like Kyriacou et al. (2009) and Tamaki et al. (2003). Storage

at 15oC presented remarkable CCL values (approximate L-values) during most of

storage period in potato chips and found superior to those placed under other

temperature regimes (5oC, 25oC) which might be due to their low corresponding

reducing sugar contents as also verified by researchers like Kaul et al. (2010) and

Biedermann-Brem et al. (2003). Appreciable CCL values were estimated at 25oC

temperature till 42nd day storage followed by considerable decline till the end of

storage. This significant decline might be associated with starch depletion along

207

with the possible participation of dehydro-ascorbic acid in chip browning during

processing as also been reported by Blenkinsop et al. (2002).


Chip crispiness (CCR) scores showed an initial increase followed by steady

decrease in T2 and T3 in contrast significant initial decline was observed in T1

which remained consistent till the end of storage period. Treatment means showed

significant difference between their CCR scores with maximum estimated in T2

followed by T3. Storage interval means demonstrated maximum CCR scores

during the 1st half of storage and minimum at the end of storage period. The

interaction between treatment means and storage intervals was found significant

with lowest CCR scores estimated in T1 and T3 on 42nd and 84rth days respectively

(Fig. 50). In different temperatures studied considerable decline in CCR scores

was observed at 5oC till the end of storage period. The initial percentage decrease

in CCR scores was around 50% on 42nd day after ward showed minor scores

(2.33/5.00) elevation till the end of storage period. Potato stored at other two

temperature regimes showed initial increase in CCR scores followed by gradual

decline. Storage at 25oC retained appreciable CCR scores till 56th day storage later

declined to lowest level (1.93/5.00) estimated on 84rth day. Storage at 15oC

presented maximum CCR scores during most of the storage period and retained

significant scores till 98th day however associated with mild decline (2.93/5.00) at

the end.

Like color, crispiness is an important quality index of processed potato

which determines the consumer acceptability. Due to its significant correlation

with this high quality product the potato chips are widely known as “potato crisps”

208

1

2

3

4

5

1 14 28 42 56 70 84 98 112 126


Cri

spin

ess

(sco

res)

5°C

15°C

25°C

Fig. 50 Chip crispiness in potato under comparative temperature storage showing highest value at 15oC (LSD (0.05) for treatment = 0.1488 LSD (0.05) for days interval = 0.2850 LSD (0.05) for interaction = 0.4705)


209

world over. Frying operation is associated with the initial decrease in chip texture

due to starch gelatinization (Anderson et al., 1994) which is followed by

progressive increase in textural attributes due to crust hardening (Pedreschi et al.,

2001) generating characteristic crispy texture. Crispiness in potato is closely

associated with the initial quality of raw material and frying medium. The presence

of high starch contents (Kita et al., 1998) and non starch polysaccharides (Kita,

2002) are considered as the key determinant of final CCR scores. In addition the

crispiness also reported to be improved by the presence of saturated fatty acids in

the frying medium (Kita et al., 2005). Since the frying medium remained constant

in the present study the retention of high quality raw material in potato stored at

15oC retained significant CCR scores during most of the storage period. Significant

decline in CCR at 5oC storage might be attributed to the starch degradation and

maillard browning before and after processing thus acceded the findings by

different researchers reported above.


Chip flavor (CFL) scores demonstrated an initial increase followed by

steady decline in T2 and T3 in contrast significant initial decrease was observed in

T1 which remained consistent till the end of storage period. Treatment means

showed maximum CFL scores in T2 followed by T3. Storage interval means

illustrated maximum CFL scores between 1st to 56th day and minimum on 126th

day. The interaction between treatments and storage intervals was found significant

with maximum scores estimated in T2 on 56th day and minimum in T1 and T3 on

70th and 84rth days respectively (Fig. 51). Storage at different temperatures during

the present study illustrated decline in flavor scores with the progress in time.

210

1

2

3

4

5

1 14 28 42 56 70 84 98 112 126


Chip

fla

vor

(sco

res)

5°C

15°C

25°C

Fig. 51 Chip flavor in potato under comparative temperature storage showing highest value at 15oC (LSD (0.05) for treatment = 0.1506 LSD (0.05) for days interval = 0.2750 LSD (0.05) for interaction = 0.4762)


211

In general CFL scores showed similar trend as in other sensorial attributes studied.

Significant decline in CFL scores was observed at 5oC which remained almost

constant till the end of storage (2.40/5.00). Storage at 15oC and 25oC retained

improved flavor scores during most of their respective storage periods however,

the eventual decline remained high at 25oC (2.00/5.00) as compare to storage at

15oC (3.30/5.00). Over all storage at 15oC maintained appreciable CFL scores than

the other studied temperature regimes.

Flavor is the combination of taste and aroma attribute in food products.

Chip Flavor scores are affected by tuber composition, frying oil quality and frying

time and temperature (Martin and Ames, 2001). Prominent chip flavor evolution

has been attributed to the frying oil composition which acts as heat transfer

medium and flavor precursor during frying (Warner et al., 1997). Maillard

reaction between reducing sugars and amino acid contents reported to produce dark

colored flavoring compounds along with suspected toxic i.e. acrylamides. The

presence of these compounds confers dark chip color and bitter flavor in processed

potato products. Amongst different chemical constituents tuber reducing sugars

and amino acids are primarily responsible for this off flavor development in potato

chips. Appreciable CFL scores identified at 15oC during storage might be

attributed to their low reducing sugars as compare to tubers stored under other

temperature regimes. The low CFL scores at 5oC due to off flavor development

might be associated with acrylamide formation during processing. The significant

relationship between chips flavor development and reducing sugars contents was

also reported by different researchers like McCann et al. (2010) and Kaul et al.

(2010).

212

4.5 EFFECT OF DIFFERENT ANTI SPROUTING AGENTS ON THE


Application of different anti sprouting agents was carried out as last

experiement of the 2nd phase of study. The response of Potato variety “Lady

Rosetta” to different anti sprouting agents like hot water treatment, spearmint oil,

clove oil and CIPC were studied. The quality attributes of potato tubers and

processing performance of potato chips were studied weekly during their post

harvest storage.

4.5.1 Effect on Weight loss (%)

Treatments with different sprout inhibitors and control showed increase in

weight loss (%) in potato during storage; however the rate of increase in weight

loss was higher in control as compare to other treatments. Treatment means and

storage interval means demonstrated significant difference amongst all the

treatments and storage intervals respectively. The interaction between treatment

means and storage intervals was found highly significant at the end of storage

where maximum weight loss percent was recorded in T1 followed by T2 (Fig. 52).

Highest weight loss (13.13%) was recorded in control whereas amongst

different anti sprouting agents CIPC application (T5) expressed lowest weight loss

(7.70%) followed by Clove Oil application (8.52%) till the end of storage period.

The application of hot water treatment (T2) and spearmint oil (T3) also retained the

tubers stability with moderate weight loss i.e. 9.25% and 10.70 % respectively as

compare to control. Amongst all treatments weight loss steadily increased due to

adequate suberization till 36 days storage (0.00% - 4.05%) which afterward

progressively increased up to 13.13 % in control as compare to 7.70%

213

0

2.5

5

7.5

10

12.5

15

1 9 18 27 36 45 54 63 72 81


Wei

ght

loss

(%

)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 52 Weight loss in response to different sprout inhibitors showing minimum loss in CIPC during potato storage (LSD (0.05) for treatment = 0.058 LSD (0.05) for days interval = 0.082 LSD (0.05) for interaction = 0.184)


214

increased up to 13.13 % in control as compare to 7.70% in CIPC treated potato by

the end of 80 days storage.

The weight loss due to respiration and evapo-transpiration triggers series of

complex metabolic activities thus considered as an important stability index for the

storage life assessment in horticultural products. The physiological phenomenon

hastens in potato as a result of sprouting under prolonged storage. The advent of

sprouts under storage obstructs the gases exchange through tuber surface which

eventually lead to the increased rate of respiration and weight loss. Pandey et al.

(2007) compared physiological weight loss in different potato varieties in response

to their sprouting behavior. He found highly significant correlation between weight

loss and sprouting behavior in selected varieties.

The present study also showed increased weight loss (%) with the onset of

sprouting in potato and found more pronounced in control. Use of different anti

sprouting agents in the present study effectively retained tuber dormancy at

varying level in potato during storage. Hot water treatment effectively retained

tuber stability till eight week storage however associated with increased weight

loss due to sprouting and tuber softening during last month of the storage. The

results partially confirmed the findings of Ranganna et al. (1998) who reported 12

weeks storage stability of potato under hot water treatment the difference in

storage stability period might be due to the tuber variety and difference in storage

temperature. The application of essential oils reported to be environment friendly

(Oosterhaven et al., 1995) and also served as protection line against insects and

pest intervention (Rajendran and Srirajini, 2007). Our results framed in the present

study showed that application of clove oil and spearmint oil effectively improved

215

the storage stability of potato with lower weight loss as compare to control. The

efficacy of clove oil application in terms of weight loss (%) was found superior to

spearmint oil and comparable to the commercial CIPC application during storage.

The response of essential oils specifically clove oil application in sprout prevention

was found highly significant which confirmed the findings reported by different

researchers like Vaughn and Spencer (1993), Kleinkopf et al. (2003), Frazier et al.

(2004), Teper-Bamnolker et al. (2010) and Chauhan et al. (2011). Minimum

weight loss (%) in CIPC application was observed in the present study however the

application of this commercial sprout inhibitor became the concern of environment

and food safety (Kleinkopf et al., 2003). Nevertheless in the present study

amongst all treatments the application of CIPC showed least weight loss (%) and

prolonged storage stability in potato during storage which coincided the previous

observations reported by Meredith, (1995), Blenkinsop et al. (2002) and Frazier et

al. (2004).

4.5.2 Effect on Total Soluble Solids (oBrix)

Total soluble solid (TSS) accumulation in potato in response to different

anti sprouting agents exhibited general increase during the storage period. The

increase in TSS was more pronounced in T1 as compare to all other treatments.

Treatment means specified lowest TSS retention in T5 and T4 which were found at

par statistically. All other treatments means showed significant difference between

them. Storage interval means in general showed non significant difference in TSS

till the mid storage which became significant during 2nd half of storage period and

found maximum at the end. In general non significant interaction between

216

treatment means and storage intervals means became significant after the mid

storage period (Fig. 53).

TSS accumulation due to different anti sprouting agents was steady during

the early weeks and progressively increased with the storage duration. Maximum

TSS accumulation was observed in Control (6.68 obrix) followed by hot water

treatment (6.40 obrix) at the end of storage. Spearmint, Clove, and CIPC retained

6.25 obrix, 6.19 obrix and 6.16 obrix TSS respectively by the same storage period

with non significant difference recorded between them.

Change in TSS is directly associated with the conversion of insoluble starch

polymers into soluble sugars (Kittur et al., 2001) and unlike other horticultural

commodities is highly redundant during potato post harvest storage. Possible

explanation for the disparity in TSS contents observed in different treatments

during the present study might be due to the starch degradation into soluble sugars

at varying levels. Sonnewald, (2001) reported that during sprouting potato tuber

turn into source organ required for the elongation of sprouts and is primarily

associated with the starch degradation into soluble sugars. The application of

different anti sprouting agents might have checked the physiological conversion of

starch into soluble sugar due to sprout inhibition. Elevated TSS contents recorded

in control and hot water treatment at the end of storage might be attributed to

increased moisture loss as compare to other treatments during storage. The

application of spearmint and clove oil presented reasonable TSS accumulation in

tubers as compare to control might be due to suppressed sprout growth. CIPC

application reported to inhibit potato sprouting by obstructing the mitotic cell

division, dislocates spindle formation (Kleinkopf et al., 2003), and supress the

217

5.4

5.7

6

6.3

6.6

6.9

1 9 18 27 36 45 54 63 72 81


Tot

al s

olu

ble

sol

ids

(oB

rix)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 53 Total soluble solids in response to different sprout inhibitors showing maximum increase in control during potato storage



218

respiration rate in potato during storage (Blenkinsop et al., 2002). In the present

investigation CIPC application retained minimum TSS contents at the end of

storage which might be attributed to suppressed respiration rate in potato tubers

thus prevented starch hydrolysis during the potato storage.

4.5.3 Effect on Sprouting (%)

In response to different anti sprouting agents data related to sprouting (%)

showed onset of sprouting in T1 and T2 by the mid storage period. Treatment

means showed minimum sprouting (%) in T6 and T5 with non significant difference

observed between them. All other treatments showed significant difference in their

sprouting (%) during storage. The storage interval means showed non significant

difference till the mid storage period which later on expressed significant

difference till the end. Significant interaction between treatments and storage

intervals was observed only during the last month storage (Fig. 54).

Potato tubers maintained their natural dormancy period irrespective of the

treatments till 1st month storage. The visible sprouts started to appear in Control

(12.17%) and hot water treated tubers (2.13%) on 36th day storage however the

percentage increase in sprouting (%) in control remained soaring and found 2-folds

as compare to hot water treated potato by the end of storage. Sprouting (%) in

control at 54rth day storage was considerably higher than those estimated in hot

water treated potato at the end of storage. Visible sprouts started to appear in

spearmint, clove and CIPC treated potatoes by 54rth, 63rd and 63rd day storage

respectively.

219

0

20

40

60

80

100

120

1 9 18 27 36 45 54 63 72 81


Spro

uting

(%)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 54 Sprouting in response to different sprout inhibitors showing maximum percentage in control during potato storage (LSD (0.05) for treatment = 1.353 LSD (0.05) for days interval = 1.913 LSD (0.05) for interaction = 4.278)


220

Lowest sprouting (%) was estimated at the end of storage in CIPC exposure

(16.40%) followed by Clove oil application (20.57%) with non significant

difference observed between them.

Tuber dormancy during post harvest storage may precisely be termed as

endo dormancy defined as the physiological tuber stage at which sprouting failed

to occur even under favorable conditions. The appearance of visible sprouts

following the period of endo dormancy is one of the peculiar features of potato

post harvest storage (Sonnewald, 2001). The onset of sprouting causes significant

economic hammering due to considerable weight loss and tuber quality

consequently increases the chance of disease attack and poor post harvest storage

life. Significant difference was observed between control and different anti

sprouting agents employed in the present study. The application of different anti

sprouting agents effectively prolonged tuber dormancy as compare to control at

ambient temperature. The use of essential oils especially clove oil exhibited almost

parallel sprouting percentage with CIPC application at ambient temperature. Our

investigations confirmed the effectiveness of different anti sprouting agents like

hot water treatments, spearmint oil, clove oil and CIPC application as reported by

previous researchers like Ranganna et al. (1998), Kleinkopf et al. (2003) and

Frazier et al. (2004).

4.5.4 Effect on Specific Gravity

Specific gravity value in potato showed initial increase followed by a

gradual decline at the end of storage. The rate of decrease in specific gravity value

was higher in T1 as compared to other treatments. Treatment means revealed non

significant difference between T4 and T5, T2 and T3 in response to different anti

sprouting agents. Storage interval means remained statistically non significant

221

during most of storage except during 1st week and last month storage. In general

except in T1 and during the last week storage interaction between treatments and

storage intervals was also found non significant (Fig. 55). Gradual specific gravity

increase witnessed in Control, hot water treatment and all other treatments till 27th

day, 45th day and 54rth day respectively and declined afterward till the end of

storage. The decline in specific gravity was highest in control (1.091) and found

lowest in CIPC application (1.107). In general maximum specific gravity values

were identified during the mid storage period amongst all the treatments.

In general the application of different anti sprouting agents affected the

specific gravity values in potato during storage as compare to control however the

influence with in the treatments remained less significant. The similar results were

reported by Cunningham et al. (1971) who studied the effect of temperatures

(38oF, 45oF and 52oF) and sprout inhibitors (MH, CIPC) on the specific gravity of

Russet Burbank potatoes and reported the value is more dependent on storage

temperature than sprout inhibitors. Claassens and Vreugdenhil (2000) reported that

potato tuber with the onset of sprouting initiated rapid depletion of starch

reservoirs eventually lead to the over all decrease in specific gravity value.

Decline in specific gravity value amongst different treatments in general and in

control and hot water treated potatoes in particular closed to sprouting confirmed

the findings reported above


Effect of different anti sprouting agents on glucose contents in potato tubers

showed steady increase during present study with considerable retention observed

in control at the end of storage. Treatment means showed significant difference

222

1.09

1.095

1.1

1.105

1.11

1.115

1 9 18 27 36 45 54 63 72 81


Spec

ific

Gra

vity

Control

Hot water

Spearmint

Clove

CIPC

Fig. 55 Specific gravity in response to different sprout inhibitors showing lowest value in control during potato storage (LSD (0.05) for treatment = 0.001620 LSD (0.05) for days interval = 0.002291 LSD (0.05) for interaction= 0.005000)


223

in recorded glucose contents with T1 retained maximum while T5 retained

minimum. Storage interval means also exhibited non significant difference with

maximum recorded in the last week while minimum during first week storage. The

interaction between storage intervals and treatments revealed significant difference

at the later stages of storage (Fig. 56).

Glucose contents continued to increase at steady pace during the 1st half of

storage and than progressively increased till the end of storage. Application of

different anti sprouting agents retained lower glucose contents (less than 100

mg/100g) than control (195.33 mg/100g) on 45th day storage however afterward

increased swiftly in control (313.0 mg/100g) and hot water treated potatoes

(207.73 mg/100g) till the end. Essential oils and CIPC applications also exhibited

increased glucose contents at the end of storage but remained below 200 mg/100g.

Non significant difference was recorded between them during most of the storage

period till pronounced increase (191.53 mg/100g) in glucose contents estimated in

spearmint treated potato at the end of storage. CIPC application maintained lowest

glucose contents (147.53 mg/100g) followed by clove oil applications (153.73

mg/100g) during the same storage period.

The prominent increase in glucose contents at the later stage of storage in

treatments like control and hot water treated potato might be due to the depletion

of carbohydrates reserves in tuber close to their sprouting (Sowokinose, 1990). The

presence of reducing sugar contents in processing potato is very critical and

negatively correlated with chip fry color (Blenkinsop et al., 2002). Potato

sprouting is primarily associated with carbohydrate mobilization i.e. conversion of

224

0

50

100

150

200

250

300

350

1 9 18 27 36 45 54 63 72 81


Glu

cose

(m

g/10

0g)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 56 Glucose in response to different sprout inhibitors showing highest increase in control during potato storage (LSD (0.05) for treatment = 1.561 LSD (0.05) for days interval = 2.207 LSD (0.05) for interaction = 4.936)


225

starch into soluble sugars required for the growth of sprouts. Burton et al. (1992)

reported elevated reducing sugar contents in potato close to sprouting as also

experienced in different treatments. To prevent potato from sprouting they are

either placed under suitable low temperature storage or exposed to different anti

sprouting agents. Different researchers like Liu et al. (1990) and Vanes and

Hartmans, (1987) reported elevated reducing sugar contents in tubers due to CIPC

application at the end of storage which was not according to our present

investigation. The possible reason might be due to comparatively less storage

duration and temperature difference established in the present study. The

application of different anti sprouting agents like Maleic hydrazide (Caldiz et al.,

2001), CIPC (Fauconnier et al., 2002), hot water treatment (Kyriacou et al., 2008)

reported to produce potato chips with better frying color due to decreased reducing

sugar contents which confirmed the results expressed in the present study.


Effect of different anti sprouting agents on total sugar in potato tubers was

found almost similar to glucose accumulation pattern during storage. General trend

was an increase in total sugar contents with time and retained significant level in

control at the end of storage period. Treatment means revealed significant

difference between potato exposed to different anti sprouting agents and those

placed as control. Storage interval means showed significant difference between all

values with maximum sugar retention at the end of storage. The interaction

between treatment and storage intervals was found highly significant after 2 month

storage period (Fig. 57).

226

800

900

1000

1100

1200

1300

1400

1 9 18 27 36 45 54 63 72 81


Tot

al s

uga

r (m

g/10

0g)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 57 Total sugar in response to different sprout inhibitors showing highest increase in control during potato storage



227

Amongst different anti sprouting agents minimum increase in total sugar

contents was recorded in CIPC (0.84% to 0.99%) followed by Clove oil (1.033 %),

spearmint oil (1.039%) and Hot water (1.107%) applications. Potato placed under

control started to accumulate substantial total sugar contents by 36th day storage

and continued to attain maximum sugar contents (1.30%) till the end of storage.

Total sugar contents are present in potato primarily in the form of non-

reducing sucrose and reducing glucose and fructose (Blenkinsop et al., 2002). The

hydrolysis of sucrose mediated through enzyme invertase may leads to the

formation of glucose and fructose monomers thus also contributing to the poor

tuber quality during storage (Kumar et al., 2004). Different anti sprouting

applications was found efficient in maintaining induced dormancy period in potato

as compare to control. These applications either as sprout inhibitor (CIPC) or

sprout suppressant (clove oil, spearmint oil, hot water treatment) maintained low

sugar contents as compare to control. The maximum sugar retention was reported

at the end of storage period in control which might be attributed to its high

sprouting percentage (as reported in table 4) at the end of storage period these

finding accede the same as stated by (Kyriacou et al., 2008), Fauconnier et al.

(2002) and Sowokinos, (1990)


The variation in starch contents in potato tubers in response to different anti

sprouting agents revealed steady initial increase followed by progressive decline

during the storage period. Data pertaining to treatment means showed maximum

starch retention in T5 followed by T4 and T3 while minimum starch contents were

228

estimated in T1 followed by T2 during the storage period. Storage interval means

expressed significant difference between them with maximum and minimum starch

retention observed on 2nd and 12th week storage respectively. Interaction between

storage interval and treatment means was found highly significant after 7th week

storage (Fig. 58). Starch contents increased initially in freshly cured potato tubers

and generally found maximum between 2nd to 4rth week storage. Hot water treated

tubers and CIPC application retained appreciable starch contents as compare to

control. Application of different essential oils (spearmint, clove) as anti sprouting

agent also maintained palpable starch contents as compare to control by the end of

storage. The percentage decline in starch contents from 1st day value was found

minimum in CIPC (13.69%) followed by Clove Oil (14.46%) applications in

contrast to maximum percentage decline observed in control (23.58%). By the end

of storage appreciable starch contents was estimated in potato exposed to different

anti sprouting agents as compare to control.

Sugars produced during photosynthetic activities in the potato leaves are

translocated to the growing potato stem tubers and stored in the form of starch

(Fernie et al., 2002). The textural attributes in potato tubers like consistency,

mealiness, sloughing etc are largely associated to its starch properties which in turn

effected by different physiologically active processes like transpiration,

redistribution and respiration. The hydrolysis of starch molecules is mediated

through the activities of gluco-amylases breaking the α-1→6 links of amylopectin

generating linear molecules of amylase which subsequently hydrolysed by

invertase and amylases to produce sucrose and reducing sugars respectively

(Marchal, 1999).

229

14.5

15.5

16.5

17.5

18.5

19.5

20.5

1 9 18 27 36 45 54 63 72 81


Sta

rch

(g/

100g

)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 58 Starch in response to different sprout inhibitors showing maximum contents in CIPC and clove during potato storage



230

The starch hydrolysishowever provides sufficient energy for the growth and

development of sprouts (Biemelt et al., 2000). In the present study use of different

anti sprouting agents maintained induced tuber dormancy and retained palpable

starch contents for more than two month as compare to control at ambient

temperature. The initial increase in starch contents was found less pronounced in

hot water treated potato and CIPC applications which might be due to the tuber

stress (Tsouvaltzis et al., 2011) and ceased mitotic activity (Meridith, 1995)

respectively. Nevertheless their application retained intact starch contents during

storage as compare to control. The application of these anti sprouting agents in the

present study for improved storage stability of potato tubers confirmed the results

reported by Ranganna et al. (1998) Frazier et al. (2004) and Kleinkopf et al.

(2003).


Total Glycoalkaloids (TGA) estimation in terms of solanine equivalent

showed steady initial increase till one month followed by progressive accumulation

by the end of storage period. The application of different anti sprouting agents on

potato tubers retained less TGA content than the control (Fig. 59). Significant

difference observed between different treatment means with maximum and

minimum contents found in T1 and T5 respectively. Storage interval means showed

significant difference in their TGA contents and found maximum at the end of

storage. The interaction between storage intervals and treatments was found

significant after 1st month storage (Fig. 59).

Increase in TGA contents remained non significant during the 1st month

storage irrespective of applied treatments. Lowest TGA content were estimated in

CIPC (47.7 mg/100g d.w) and clove oil (53.70 mg/100g d.w) application at the

end of storage which were found parallel to those identified in control on

231

5

25

45

65

85

105

1 9 18 27 36 45 54 63 72 81


TG

A (

mg/

100g

d.w

)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 59 Total glycoalkaloids in response to different sprout inhibitors showing lowest increase in CIPC and clove during potato storage (LSD (0.05) for treatment = 0.9058 LSD (0.05) for days interval = 1.2810 LSD (0.05) for interaction = 2.8650)


232

45th day storage. Amongst different anti sprouting agents marked increase in

TGA contents (50.70 mg/100g d.w and 58.30 mg/100g d.w) started in hot water

treatment and spearmint oil on 63rd and 72nd days of storage respectively. The

progressive increase in TGA contents observed in control and hot water treated

potato after the mid storage period and exceeded the safe human intake limit i.e.

20mg/100g f.w (Mensinga et al., 2005) on 72nd (83.43 mg/100g d.w) and 81st

(79.47 mg/100g d.w) days respectively.

Smith et al. (1996) studied TGA contents in different part of potato plant

and reported maximum concentration in sprouts and flowers. Similar

observations have been reported by Kozukue et al. (2001) who determined high

TGA contents in potato is proportional to their sprouting potential during storage.

Nema et al. (2008) reported that sprouting is one of the principal factors

responsible for glycoalkaloids formation in potato during post harvest storage.

Application of different anti sprouting agents retained TGA contents with in the

food safety at ambient temperature except in hot water treated potato at the end of

storage. Our results revealed significant TGA contents in control and hot water

treated potato that might correspond to their high sprouting percentage observed

at the end of storage. Similar close relationships between TGA contents and

potato sprouting were also reported by other researchers like, Sengul et al.

(2004), Friedman et al. (2003) and Percivel et al. (1993).

233


In general Total Phenolic Contents (TPC) estimated in terms of gallic

acid equivalent expressed initial increase followed by gradual decline till the

end of storage period. Significant retention of TPC however observed in

different treatments as compare to control. Treatment means showed

significant difference in their TPC in response to different anti sprouting

applications. T4 maintained maximum TPC followed by T5 while minimum

were observed in T1. Storage Interval means expressed significant

differences with maximum and minimum TPC determined after one month

and before the start of storage respectively. The interaction between

treatments and storage intervals showed maximum TPC contents in T3 and

T4 on 54rth day storage (Fig. 60).

TPC increased amongst all treatments till 36th day storage and

afterward started to decline in control till the end of storage. Significant

decline in TPC in response to different anti sprouting agents witnessed after

63rd day storage however the final retention amongst treatments remained

variable. CIPC (143.50 mg/100g) and clove oil (142.57mg/100g) application

retained appreciable TPC even after 80 days storage and found around

double than that estimated in control (70.17 mg/100g) during the same

period. Amongst different anti sprouting agents Clove and spearmint

applications retained maximum TPC accumulation through out the storage

period.

234

60

90

120

150

180

1 9 18 27 36 45 54 63 72 81


TP

C (

mgG

AE

/100

g d

.w

Control

Hot water

Spearmint

Clove

CIPC

Fig. 60 Total phenolic contents in response to different sprout inhibitors showing maximum retention in CIPC and clove during potato storage (LSD (0.05) for treatment = 1.731 LSD (0.05) for days interval = 2.448 LSD (0.05) for interaction = 5.474)


235

Biosynthesis of TPC involves de amination of amino acid phenyl

alanine which acts as their precursor (Hamauzu, 2006). TPC bestow

significant functional attributes to fruits and vegetables groups owing to

their high anti oxidant activity (Kaur and Kapoor, 2002). Maximum retention

of TPC in potato tubers during storage is associated with low polyphenolase

activity which is responsible for potato browning (Anthon and Barrett, 2002).

Sufficient retention of TPC was observed in clove and spearmint oil

applications however the eventual decline in spearmint oil was more

prominent due to sprouting. In contrast to essential oils (Clove and

spearmint) increase in TPC during storage was found less prominent in CIPC

and hot water treatments which might be due to mitotic inhibition (Kleinkopf

et al., 2003) and degradation of heat sensitive phenolic substances (Kalt et

al., 2005) respectively conferred by applied anti sprouting agents. Our

results revealed considerable effect of anti sprouting agents on TPC

retention in stored potatoes as compare to control. The presence of sufficient

molecular oxygen and subsequent sprouting in control caused significant

decline in TPC as compare to other treatments.


Radical scavenging activity (RSA) estimated in terms of % inhibition

of DPPH showed minor initial increase followed by gradual decrease during

potato storage. The decrease in RSA was highly pronounced in control as

compare to other treatments. Treatment means showed significant difference

between them with T4 maintained maximum activity followed by T5 and T3.

T1 showed least RSA activity during storage period followed by T2. Storage

236

interval means showed maximum activity after one month storage which

afterward declined with time and found minimum at the end of storage.

Interaction between treatments and storage intervals was found significant

with maximum activity recorded in T4 on 45th day storage (Fig. 61).

In general steady initial increase was observed at the start of storage

in all treatments which became highest by the end of 1st month. Unlike

gradual decline observed afterward in control and hot water treated potatoes

the activity continued to increase in CIPC, clove oil and spearmint oil till

45th day storage. Amongst different anti sprouting agents CIPC (38.20%)

and clove oil (37.73%) applications retained substantial activity till the end

of storage. Application of spearmint and hot water treatment also presented

sufficient activity i.e. 24.67% and 24.57% respectively as compare to control

(19.50%) and found statistically similar at the end of storage.

Fruits and vegetables due to their high flavonoids, vitamins,

tocopherols and poly phenolic contents carry high radical scavenging

activity (Chu et al., 2000). In the present investigation general initial increase

in RSA activity during 1st month storage might be due to the increase in total

phenolic contents during the start of storage period (Padda and Picha, 2008).

The subsequent decrease in RSA activity in control followed by hot water

treatment and spearmint oil application might be due to the loss of ascorbic

acid and tissue senescence (Srilaoung and Tatsumi, 2003). The sprouting in

potato is associated with the remarkable increase in reactive oxygen species

like hydrogen per oxide (H2O2) (Bajji et al., 2007). The stability in RSA

activity was observed along the onset of sprouting in control might be due

237

10

20

30

40

50

60

1 9 18 27 36 45 54 63 72 81


RSA

(%

)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 61 Radical scavenging activity in response to different sprout inhibitors showing highest activity in CIPC and clove during potato storage (LSD (0.05) for treatment = 0.6474 LSD (0.05) for days interval = 0.9155 LSD (0.05) for interaction = 2.0470)


238

to the pronounced activities conferred by anti oxidant enzymes like

peroxidases and catalases against these reactive oxygen species. Our results

revealed that application of different anti sprouting agents were found

effective in maintaining appreciable RSA activity in turn better storage

stability as compare to control.


In response to different anti sprouting agents polyphenol oxidase (PPO)

activity in potato showed steady increase with the progression in the storage

period however the increase was found more momentous in control as compare to

other treatments. Treatment means demonstrated maximum activity in T1

followed by T3 while minimum were recorded in T2, T4 and T5 and were found

statistically similar. Storage interval means showed minimum PPO activity till 1st

week and than increased significantly till the end of storage. Interaction between

storage intervals and treatments was significant with maximum activity estimated

in T1 during last month storage (Fig. 62).

Except in hot water treated potato amongst all the treatments studied PPO

activity continued to increase steadily with no sign of termination till the end of

storage time. The increase in PPO activity was highly significant (76.88 U/g) in

control with more than 2-folds increase at the end of storage. Hot water treatment

presented significant reduction in their PPO activity and remained lower than

their 1st day value till 45th day storage followed by around 2-folds (60.89 U/g)

increase till the end of storage time. Enzyme activity observed in different anti

sprouting agents including the hot water treatments at the end of storage

239

15

30

45

60

75

90

1 9 18 27 36 45 54 63 72 81


PP

O (U

/g d

.w)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 62 Polyphenol oxidase in response to different sprout inhibitors showing lowest enzymatic activity in CIPC and clove during potato storage (LSD (0.05) for treatment = 0.4146 LSD (0.05) for days interval = 0.5863 LSD (0.05) for interaction = 1.3110)


240

(81st day) was found less than that estimated in control on 45th day storage.

Moderate PPO activity observed in spearmint oil application and showed

deviation from clove and CIPC applications after 54rth day storage. CIPC (42.72

U/g) and clove oil (43.94 U/g) applications presented similar PPO activity

through out the storage time with non significant difference recorded between

them.

Enzymatic browning in potato may cause substantial commercial loss and

is primarily associated with the activities of peroxidase and polyphenol oxidase

enzymes (Loaiza and Saltveit, 2001). Nourian et al. (2003) studied transition in

quality attributes and enzyme kinetics in potato stored under different

temperature regimes. He concluded steady increase in PPO activity with the

increase in storage period at ambient temperature. PPO activity remained steady

during 1st month storage in most of the treatments except in hot water treated

potato due to efficient post harvest handling however, increased after ward till the

end of storage. Hot water treatment caused significant reduction in activity during

1st month storage due to enzyme inactivation and thus considered advantageous

in preventing potato browning during subsequent processing. Decline in PPO

activity as result of hot water treatment has also been reported by Yemenicioglu

(2002) in potato, Kim et al. (1993) in apple and Rodriguez-Lopez et al. (1999) in

mushrooms. Decreased PPO activity as results of hot water treatment might be

due to the conversion of oligomeric (active) into monomeric (less active)

configuration which also in lines with the findings of Cho and Ahn, (1999) who

reported de-polymerization of PPO enzyme due to mild heat treatment. Similar

observations regarding reduction in PPO activity has also been reported by

241

Tsouvaltzis et al. (2011) in hot water treated potato slices during storage. The

activity increased steadily afterward in all treatments due to the availability of

substrate and its subsequent oxidation during storage as also reported by the

researcher above. The increased PPO activity in fruits and vegetable during post

harvest storage is also attributed to the moisture loss and senescence (Bryant,

2004) which leads to subsequent sprouting in potato. Our results showed that

high PPO expression closer to potato sprouting might be as a part of plant

defense mechanism and taken as an index of plant response to different stress

conditions which has also reported by Afify et al. (2012). Application of different

anti sprouting agents in the present investigation prevented potato sprouting there

by averted stress conditions consequently presented lower PPO activity as

compare to control during the storage.


In response to different anti sprouting agents’ steady increase in

Peroxidase (POD) activity was observed in all the treatments with maximum

activity estimated in control during storage. Treatments means showed maximum

POD activity in T1 while minimum activity observed in T4 and T5 which were

found statistically similar (α-0.05). Storage interval means showed maximum

POD activity at the end while minimum estimated during the start of trial.

Interaction between storage intervals and treatment was significant after 1st

month storage and found highest POD activity in control on D6 onwards till the

end of storage. Irrespective of different treatments the POD activity remained

steady during 1st month storage (Fig. 63).

242

6

13

20

27

34

41

1 9 18 27 36 45 54 63 72 81


PO

D (U

/100

g f.w

)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 63 Per oxidase in response to different sprout inhibitors showing lowest enzymatic activity in CIPC and clove during potato storage (LSD (0.05) for treatment = 0.0966 LSD (0.05) for days interval = 0.3833 LSD (0.05) for interaction = 0.8572)


243

Steady increase in POD activity observed in all the treatments during 1st

month of storage. Unlike PPO, POD activity continued to increase in hot water

treated potato during the storage period with 2-folds estimated at the end of

storage. The over all increase in POD activity was highest (37.83 U/100g) in

control followed by hot water treatment (25.80 U/100g) and found lowest in CIPC

(17.50 U/100g) and clove oil (17.82 U/100g) applications at the end of storage.

Application of spearmint oil as anti sprouting agent presented moderate enzymatic

activity (20.75 U/100g) during the same storage period.

The Increased POD activity is associated with the oxidation of phenolic

compounds under physiological stress causing decay and loss of quality during

storage (Ding et al., 2006). Aydin and Kadioglu, (2001) reported increased POD

activity in fruits and vegetables under stress conditions like progression in their

physiological stages i.e. ripening, senescence which also observed in the present

investigation.

Our results showed in general increased POD activity in all the treatments

as also observed by Nourian et al. (2003) at ambient temperature storage. POD

being more stable in storage atmosphere under stress conditions (Anthon and

Barrett, 2002) showed low percentage increase as compare to PPO. Results also

showed non significant effect of hot water treatment on POD activity which

confirmed the finding reported by Yemenicioglu, (2002). Delaplace et al. (2008)

reported that essential oil application prevent potato from disease incidence due to

their anti viral and anti fungal characteristics. In addition their application prevents

potato sprouting by inhibition of plant growth activities due to their increased

volatility (Arif et al., 2010). In the present study application of different sprout

244

inhibitors effectively prevented potato sprouting as compare to control, and their

lower relative enzymatic activity close to 1st day value might be taken as an index

of better storage stability of potato. Similar enzyme activities in response to

different anti sprouting agents have been reported Afify et al., (2012).

4.5.13 Effect on Chip Moisture Content

Chip moisture contents (CMC) increased with storage time irrespective of

different anti sprouting agent. Treatment means showed maximum moisture

contents in T1 followed by T2 while, T5 followed by T4 retained minimum moisture

contents. Storage interval means showed minimum CMC after the first week while

maximum contents were recorded at the end of storage. The interaction between

treatments and storage intervals was found significant with maximum chip

moisture contents estimated in T1 during last ten days storage (Fig. 64). In general

in all treatments increase in chip moisture contents was found steady and treatment

effect remained statistically less significant till 54rth day storage. The increase in

CMC was highly pronounced in control and hot water treated potato after 63rd and

81st day storage. CMC at the end of storage was found more than 2-folds than that

estimated at the start of experiment. Moderate CMC were estimated in spearmint

oil application at the end of storage however found statistically at par with clove

oil and CIPC applications during most of storage period. Lowest percentage

increase in CMC was estimated in clove oil and CIPC application i.e. 40% and

37% in contrast to 162% increase in control at the end of 81st day storage.

Frying of potato chip is associated with two parallel processes of moisture

loss and fat uptake (Mellema, 2003). During thermal processing of the potato chips

245

1

1.5

2

2.5

3

1 9 18 27 36 45 54 63 72 81


Chip

moi

sture

con

tents

(%

)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 64 Chip moisture contents in response to different sprout inhibitors showing highest value in control during potato storage (LSD (0.05) for treatment = 0.03968 LSD (0.05) for days interval = 0.05612 LSD (0.05) for interaction = 0.12550)


246

moisture content present in potato tuber evaporates leaving the structural

reservoirs available for subsequent oil uptake (Basuny et al., 2009). The presence

of high moisture contents in processed potato products are highly undesirable due

to less storage stability and poor sensorial attributes. Potato with intact starch

contents and high specific gravity value were reported to produce potato chips

with low moisture contents (Pinthus et al., 1995). Sprouting in potato tubers are

associated with starch hydrolysis (Biemelt et al., 2000) thus would be producing

chips contents with high CMC and poor sensorial scores. The application of

different anti sprouting agents retained appreciable starch contents thus produced

potato chips with low moisture contents as compare to control. Significant

increase in CMC in control and hot water treated potato due to excessive

sprouting at the end of storage supports significant correlation between these two

phenomenons.


Irrespective of different anti sprouting agents general trend was an

increase in Chip fat absorption (CFA) with storage period. Treatment means

demonstrated significant difference between them with minimum CFA in T5

followed by T4. Maximum CFA was estimated in T1 followed by T2 during the

storage period. The storage interval means showed lowest CFA till 3rd week

storage and found highest at the end. The interaction between storage intervals

and treatment means became highly significant after one month and found

highest CFA in T1 after 2nd month till the end of storage (Fig. 65).

247

Application of different anti sprouting agents presented significant difference in

CFA during the present study. The percentage CFA increase was lower in

different anti sprouting applications like CIPC (24%), Clove oil (25.5%),

spearmint oil (32.1%) hot water treatment (44.5%) in contrast to control

(61.50%) at the end of storage. CIPC and clove oil application were found

equally effective with lowest CFA estimated at the end of storage. The CFA

estimated in CIPC and clove oil applications on 81st day were lower than that

estimated in control on 45th day. Over all control presented highest CFA on 54rth

day with continuous increase till the end of storage.

Fat absorption in potato chips during frying is largely associated with the

starch contents and specific gravity value of the raw material (Kita, 2002). The

onset of sprouting associated with starch hydrolysis resulted in increased fat

absorption in control and hot water treated potato which confirmed the finding of

Biemelt et al. (2000) who reported significant degradation of starch contents in

potato tubers during sprouting in order to provide required energy for sprout

development.

In the present study application of different anti sprouting agents were

found not only effective as sprout suppressants but also exhibited appreciable

retention of starch contents and high specific gravity value. This inverse

relationship between tuber specific gravity and their corresponding fat absorption

during potato processing has also been reported by different researchers like

Basuny et al. (2009), Kita, (2002) and Mehta and Swinburn, (2001).

248

25

30

35

40

45

50

1 9 18 27 36 45 54 63 72 81


Chip

fat

abso

rption

(%

)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 65 Chip fat absorption in response to different sprout inhibitors showing highest contents in control during potato storage (LSD (0.05) for treatment = 0.4136 LSD (0.05) for days interval = 0.5850 LSD (0.05) for interaction = 1.3080)


249


Chip Color (CCL) estimated as approximate L-value showed steady

decrease with the increase in storage time. The treatments means showed highest

CCL value in T5, T4 and T3 and were found statistically similar (at α= 0.05) while

lowest CCL values were identified in T1 followed by T2. Storage interval means

showed maximum CCL values during the first month which afterward declined

steadily till the end of storage. The interaction between treatments and storage

intervals became significant after mid storage with maximum CCL value estimated

at the start and minimum in T1 followed by T2 at the end of storage period (Fig.

66). The application of different anti sprouting agents expressed higher CCL value

as compare to control however the difference between them was less significant.

Statistically the effect of different anti sprouting agents on CCL values remained

similar except some decline expressed in hot water treatment at the end of storage.

Over all the percentage decline in CCL value was found maximum in T1 (20.0%)

followed by T2 (15.3%) at the end of storage period.

Chip Color is the most imperative quality parameter in producer`s

prospective as well sets consumer preference (Segnini et al., 1999). Reducing

sugar contents in potato tubers are key determinant of color development in potato

chip color during frying which is primarily attributed to their participation in

Maillard reaction along with protein fractions (De Wilde et al., 2004).

During the start of experiment irrespective of treatment the CCL values

remained statistically similar however started to decrease with storage time. The

decrease in CCL value was significant in control which might be due to increased

250

50

55

60

65

70

1 9 18 27 36 45 54 63 72 81


Chip

col

or (L

-val

ue)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 66 Chip color in in response to different sprout inhibitors showing highest scores in CIPC and clove during potato storage


251

starch degradation into monosaccharides due to high sprouting percentage as also

reported by Biemelt et al. (2000). Decreased color scores in control was also

attributed to enzymatic browning at the end of storage period (Mendoza et al.,

2007). The presence of brown spots in potato chips caused poor color scores in

finished product. Another possible reason of low CCL values in control and hot

water treated potato was due to increased fat absorption which conferred oily

appearance on the chip surface. The undesirable color estimation due to increased

fat absorption was also reported by different researchers like Bouchon and Pyle,

(2004) and Rimac-brncic et al. (2004). The application of different anti sprouting

agents were found effective in sprout prevention, starch retention and browning

control thus retained better color scores as compare to control which confirmed the

findings reported by different researchers above.


Chip crispiness (CCR) scores exhibited initial increase during the start of

storage followed by steady decrease with the progress in storage period. The rate

of decrease in CCR scores was higher in control as compare to all other treatments.

Treatment means revealed non significant difference in T3, T4, and T5 in their CCR

scores with minimum and maximum values estimated in T1 and T6 respectively.

Storage interval means showed highest CCR scores during mid intervals and

lowest at the end of storage. Significant interaction observed between treatments

and storage intervals with maximum CCR scores estimated in T3, T4 and T5 on

36th, 36th and 45th day respectively (Fig. 67). The application of different anti

sprouting agents retained considerable CCR scores till 45th day storage afterward

declined till the end.

252

1

2

3

4

5

1 9 18 27 36 45 54 63 72 81


Chip

cri

spin

ess (s

core

s)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 67 Chip crispiness in response to different sprout inhibitors showing highest scores in CIPC and clove during potato storage



253

Amongst different treatments percentage decline in CCR scores was found highest

in control (58.4%) followed by hot water treated potato (46.2%). Appreciable CCR

scores were identified in spearmint oil application during most of the storage time

however decreased (3.23/5.00) significantly at the end of storage. CIPC and Clove

oil applications maintained highest CCR scores i.e. 4.00/5.00 and 3.80/5.00

respectively till the end and found statistically similar through out the storage

period.

The particular textural attribute “crispiness” is also synonym for potato

chips i.e. potato crisps is an important quality parameter in setting consumer

preference for processed potato products. Crispiness in potato chips is dependent

on different factors like starch, contents (Kita, 2002), pectin substances (Chang et

al., 1993), fat absorption (Basuny et al., 2009) and superior processing techniques

(Mehta and swinburn, 2001).) The application of different anti sprouting agents

particularly essential oils and CIPC application retained appreciable starch and

pectin contents thus produced potato chips with lower fat and consequent superior

CCR scores as compare to control. The same inverse relationship between chip

crispiness and fat absorption was also reported by Kita et al. (2002). The onset of

sprouting in control resulted in starch hydrolysis and pectin degradation eventually

resulted in decline in textural symmetry and poor CCR scores in potato chips.


Chips flavor (CFL) in general showed an initial increase till mid storage

followed by a progressive decline till the end of storage (Fig. 68). The treatment

means showed minimum CFL scores in T1, followed by T2. T3, T4 and T5 retained

254

highest CFL scores with non significant difference recorded between them. The

storage interval means showed maximum CFL scores during the mid intervals

while minimum were expressed at the end of the storage. The interaction between

storage intervals and treatments showed minimum (1.85/5.00) and maximum

(4.67/5.00) scores in T1 and T3 respectively at different storage intervals (Fig. 68).

Different anti sprouting agents retained appreciable CFL scores till 54rth day

afterward decreased by the end of storage time. The retention of CFL scores were

found highest in CIPC (3.97/5.00) treated potato followed by clove oil (3.77/5.00)

and spearmint oil (3.23/5.00) applications till the end of storage. Highest

percentage decline in CFL scores was observed in control (56.6%) followed by hot

water treated potato (55.5%).

Flavor evolution in potato chips is primarily attributed to the oil uptake and

corresponding volatile formations during thermal processing. The principal factor

effecting Chip flavor are tuber composition, temperature and time of frying, and

frying oil composition (Martin and Ames, 2001). The major aromatic compounds

produced in chip processing are phenyl acetaldehyde, methyl pyrazines, hexanal,

and decadienal (Kondjoyan and Berdague, 1996). The presence of phenolic

compounds, carbohydrates and proteins act as precursor for flavor production in

potato chips during thermal processing (McCann et al., 2010). Application of

different anti sprouting agents showed appreciable flavor scores in potato chips due

to better retention of these organic precursors during storage as compare to control.

255

1

2

3

4

5

1 9 18 27 36 45 54 63 72 81


Ch

ip f

lavo

r (s

core

s)

Control

Hot water

Spearmint

Clove

CIPC

Fig. 68 Chip flavor in response to different sprout inhibitors showing highest scores in CIPC and clove during potato storage


256

4.6 EFFECT OF INTEGRATED TREATMENTS ON THE QUALITY

ATTRIBUTES OF POTATO

In the last phase of study an integrated post harvest management approach

was planned on the basis of results obtained in the 1st and 2nd phase of the study.

Potato variety “lady Rosetta” was treated with hot water (55 ±2oC for 15 minutes)

followed by Clove Oil application (1%). Afterward the tubers were packed in

polypropylene bags and stored at 10 ±1oC temperature and 75± 5% R.H to assess

their eventual post harvest storage life. Physico-chemical and functional assays in

potato tubers were carried out at an intervals of twenty days. In addition, potato

chips prepared from treated potato were coated with different levels of Aloe vera

gel before frying and their subsequent processing attributes were studied at an

interval of thirty days.


General trend was increase in weight loss (%) during storage and was

found highly prominent in control than in integrated treatment. Treatment means

illustrated significant difference between them with T1 retained higher weight loss

than T2. Storage interval means showed maximum weight loss on 80th followed by

60th days whereas the minimum weight loss was estimated on 1st day. Interaction

between storage intervals and treatments showed highest weight loss estimated in

T1 on 80th day (Fig. 69).

Weight loss increased with the progression in storage duration however

remained modest during 1st month storage in both treatments. Significant increase

in weight loss experienced in T1 on 40th day (5.86%) and continued to increase

with maximum 12.98% weight loss on 80th day in contrast 2.48% recorded in

integrated treatment during same storage period.

257

0

3

6

9

12

15

1 20 40 60 80 100 120 140 160 180Storage intervals (day)

Wei

ght

loss

(%

)

T1 (Control)

T2 (Treatment)

Fig. 69 Weight loss in response to integrated treatment showing minimum loss as compare to control during storage (LSD (0.05) for treatment = 0.0495 LSD (0.05) for interval = 0.1107 LSD (0.05) for interaction = 0.1566)


258

Weight loss estimated in tubers after that was not carried out due to their

excessive sprout initiation. Integrated treatment effectively reduced weight loss

(%) with steady increase estimated during most of the storage period. In

comparison weight loss (%) estimated in integrated treatment (7.32%) on 180th day

storage was significantly lower than that estimated in control (10.75%) on 60th day.

Potato storage is carried out with strict emphasis on the reduction in weight

loss (%) by preventing excessive respiration. Respiration along with sprouting is

associated with the conversion of valuable starch into soluble sugar which

consequently degraded in to water, carbon dioxide and energy (Fennir, 2002). The

application of different modified atmosphere packaging along with suitable storage

conditions was found effective in reduction in weight loss (%) in horticultural

commodities (Abbasi et al., 2011). Our results showed that the application of

polypropylene packaging (Conte et al., 2009), appropriate storage temperature

(Nourian et al., 2003) and clove oil application (Kleinkopf et al., 2003) prevented

excessive weight loss (%) with ultimate increase in storage stability of potato as

compare to control.


General trend showed increase in Total Soluble Solids (TSS) during storage

in both treatments with the increase in storage duration. Treatment means showed

significant difference between them with higher TSS accumulation estimated in T1

as compare to T2. Storage interval means was found significant with lowest TSS

retention on 1st and highest on 80th days. Interaction between treatments and

259

storage intervals was significant with maximum TSS accumulation in T1 on 80th

followed by 60th days (Fig. 70).

TSS increased with the increase in storage duration with highest over all

16.5% increase estimated in control on 80th day. Integrated treatment maintained

lower TSS accumulation during most of the storage period with non significant

increase estimated during 1st month storage. TSS increased steadily afterward with

eventual 6% increase estimated on 180th day. Over all integrated treatment

maintained radically lower TSS as compare to control during storage period.

TSS is associated with increased soluble solids concentration and is

primarily attributed to the soluble sugar contents in fruits and vegetables (Abbasi et

al., 2011). Enzyme mediated conversion of starch into sugar particularly at low

temperature storage and considered highly undesirable for loss of color in

processed potato products (Kumar et al., 2004).

In the present study integrated treatment retained lower TSS contents as

compare to control owing to their reduced rate of respiration under modified

atmosphere packaging and lower temperature storage which confirmed the findings

reported by researchers like Abbasi et al. (2011), Sammi and Masud, (2007),

Nourian et al. (2003) etc. The application of clove oil application prevented the

onset of sprouting which also been related to the increase in starch depletion during

storage hence facilitated lower TSS accumaltion during storage as also been

observed by Sonnewald, (2001).

260

5.4

5.8

6.2

6.6

7

1 20 40 60 80 100 120 140 160 180


Tot

also

lub

le s

olid

s (°

bri

x)

T1 (Control)

T2 (Treatment)

Fig. 70 Total soluble solids in response to integrated treatment showing lower contents as compare to control during storage

(LSD (0.05) for treatment = 0.00577 LSD (0.05) for intervals = 0.01167 LSD (0.05) for interaction = 0.01650)


261

4.6.3 Effect on Sprouting

General trend showed increase in sprouting potential in both treatments

with the increase in storage duration. Treatment means revealed significantly

higher sprouting (%) in T1 as compare to T2. Storage interval means expressed non

significant difference with in 1st, 20th, 100th days, and 140th, 160th, 180th days with

over all maximum percentage estimated in 80th day. The interaction between

treatments and storage intervals was significant with maximum sprouting (%)

estimated in T1 on 80th day (Fig. 71).

Sprouting (%) started to increase in control on 40th day (18.68 %) and

continued at progressive rate till 80th day (92.43%) storage. In contrast integrated

treatment retained complete tuber dormancy till 100 days afterward presented

steady increase in sprouting (%) which remained minimal on 180th day (6.55%)

storage.

Extension in tuber dormancy and reduction of post harvest losses are the

critical factors in potato storage. Sprouting at the end of endo dormancy is one of

the peculiar features of potato (Sonnewald, 2001) which is associated with

substantial economic loss to the grower and processor. Our results showed

remarkable reduction in sprouting (%) in response to integrated treatments as

compare to control. Individual application of hot water treatment followed by

ambient storage (discussed in experiment-2) presented tuber softening however

followed by storage at 10 ±1oC in the present study retained tuber firmness till the

end of storage period. Potato tubers retained intact compositional attributes in

response to hot water treatments, clove oil application, polypropylene packaging,

and storage at 10 ±1oC temperature. The combined effect of these loss reduction

techniques prevented tuber sprouting for six month. The results presented in the

262

0

20

40

60

80

100

1 20 40 60 80 100 120 140 160 180


Sp

rou

tin

g (%

)

T1 (Control)

T2 (Treatment)

Fig. 71 Sprouting in response to integrated treatment showing lower percentage as compare to control during storage (LSD (0.05) for treatment = 0.989 LSD (0.05) for interval = 2.212 LSD (0.05) for interaction = 3.128)


263

present investigation are found in line with the findings of Kyriacou et al. (2008),

Song, (2009) and Knowles et al. (2009).


Data pertaining to glucose contents showed increasing trend with the

progression in storage period in both the treatments. Treatments means showed

significant difference between them with maximum value estimated in T1. Storage

interval means exhibited non significant difference between 60th and 120th days

while all other differed significantly at 5% level of significance. The interaction

between treatments and storage interval was significant with maximum glucose

contents observed in T1 on 80th day (Fig. 72).

Slow increase in glucose contents observed till 20th day storage in both

treatments there after showed progressive and moderate increase in control and

integrated treatments respectively. Control tubers accumulated maximum glucose

contents (340.13 mg/100g) on 80th day after ward discarded due to excessive

weight loss and increased sprouting. Integrated treatments illustrated slow glucose

accumulation during most of the storage period however retained substantial

ultimate glucose contents (323.33 mg/100g). In comparison glucose contents

estimated in T1 on 80th day were found higher than that quantified in T2 on 180th

day.

Sweetening response of potato tubers is associated with low temperature

(Driskill et al., 2009) and potato sprouting due to rapid starch depletion (Biemelt,

2000) during the storage period. The present study revealed that the steady increase

in glucose contents during storage was largely function of storage duration rather

than storage temperature. Glucose contents started increasing at the onset of

264

0

80

160

240

320

400

1 20 40 60 80 100 120 140 160 180


Glu

cose

(m

g/10

0g)

T1 (Control)

T2 (Treatment)

Fig. 72 Glucose in response to integrated treatment showing lower contents as compare to control during storage (LSD (0.05) for treatment= 3.327 LSD (0.05) for interval= 6.773 LSD (0.05) for interaction= 9.579)


265

Sprouting and tuber senescence (Sonnewald, 2001) which was highly significant in

control than integrated treatment. Integrated treatments affectively retained low

sugar accumulation during most of the storage duration. Storage at 10 ±1oC

temperature was found tolerant enough for potato tubers against low temperature

sweetening. The use of polypropylene packaging (Calderon, 2008) along with

clove oil application (Song, 2009) prevented weight loss and tuber sprouting

respectively there by prevented tubers from senescence sweetening (Kumar et al.,

2004) which confirmed the results reported by previous researchers as above.

4.6.5 Effect on Total Sugar

General trend was an increase in total sugar contents with the progression

in storage period. Treatment means showed significant different between them

with T1 retained higher total sugar contents than T2. Storage interval means also

demonstrated significant difference with maximum sugar contents estimated on

180th day and minimum at the start of experiment. Interaction between treatments

and storage intervals was significant with maximum sugar contents identified in T1

followed by T2 on 80th and 180th days respectively (Fig. 73).

Total sugar contents in potato are present primarily in the form of glucose,

fructose and sucrose produced as a result of starch degradation during storage

(Knowles et al., 2009). Reducing sugars like glucose and fructose reported to

participate directly in mallaird browning where as sucrose acts as transient balance

in starch breakdown thus both confer significant commercial loss in potato

(Kyriacou et al., 2009). Sugar accumulation became more significant at low

temperature due to cold induced sweetening hence identification of

266

850

950

1050

1150

1250

1350

1450

1 20 40 60 80 100 120 140 160 180


Tot

al s

uga

rs (

mg/

100g

)

T1 (Control)

T2 (Treatment)

Fig. 73 Total sugar in response to integrated treatment showing lower contents as compare to control during storage

(LSD (0.05) for treatment= 6.85 LSD (0.05) for interval= 15.46 LSD (0.05) for interaction= 21.87)


267

critical temperature for the storage of selected variety is very important (Kumar et

al., 2011). Though the sugar metabolism is primarily associated with the storage

temperature however its elevated concentration has also been reported in potato

tuber close to sprouting (Fauconnier et al., 2002). The application of integrated

treatments prevented accumulation of sugar contents during storage along with

positive varietal response to the storage temperature (10 oC) and anti sprouting

agent (clove oil). The selected temperature and anti sprouting agents maintained

significantly lower sugar contents as compare to control. Considerably higher

sugar contents in control might be due starch degradation trailed by tuber

senescence and increased sprout percentage during storage which was also

reported by Fauconnier et al. (2002) and Swokinose, (1990).

4.6.6 Effect on starch

Starch contents in general showed decreasing trend with the increase in

storage duration in both treatments studied. Treatments means revealed significant

difference between their starch contents with T2 retained higher contents than T1.

Storage interval means showed significant difference in their starch contents with

maximum and minimum values estimated during the start and the end of

experiment respectively. The interaction between treatments and storage intervals

was also significant with lowest starch contents estimated in T1 on the 80th day of

storage (Fig. 74).

Amongst both treatments starch contents decreased with the progression in

storage period however the decrease was more rapid in control than that observed

in integrated treatment. Steady increase and decrease in starch content was

estimated in T2 and T1 respectively on 20th day.

268

15

16

17

18

19

20

1 20 40 60 80 100 120 140 160 180


Sta

rch (g/

100g

)

T1 (Control)

T2 (Treatment)

Fig. 74 Starch in response to integrated treatment maintaining higher contents as compare to control during storage (LSD (0.05) for treatment= 0.0466 LSD (0.05) for interval= 0.1044 LSD (0.05) for interaction= 0.1476)


269

Afterward steady and progressive decline was observed in integrated treatment and

control correspondingly during the rest of the storage period. The highest

percentage decline (18%) was observed in control on 80th day whereas the ultimate

percentage decline in integrated treatment was 12.5% on 180th day.

. Starch is the principal carbohydrate present in potato and governs the

physical quality attributes of potato like specific gravity, dry matter etc (Singh et

al., 2008). Potato tuber is not an inert body owing to its continuous conversion of

starch in to soluble sugars during storage. Starch depletion along with concurrent

sugar accumulation is extremely undesirable post processing disorder being faced

by the processor during potato storage (Tamaki et al., 2003). The energy required

by the dormant tuber during sprouting largely dependent on their starch

degradation (Biemelt et al., 2000). In the present investigation starch depletion in

control tubers might be due to increased respiration rate and sprout initiation.

Integrated treatment offered modified atmosphere packaging to restrain respiration

rate (Conte et al., 2009) augmented by suitable temperature storage (Karim et al.,

2008) and anti sprouting agents (Frazier et al., 2004) there by retained intact starch

contents as compare to control.

4.6.7 Effect on Ascorbic Acid

General trend showed decrease in ascorbic acid (AA) contents during

storage in both treatments. Treatment means showed significant difference

between their ascorbic acid contents with integrated treatment retained higher AA

contents as compare to control. Storage interval means illustrated significant

difference between them with maximum and minimum AA contents estimated at

270

the start and end of storage period respectively. The interaction between treatments

and storage interval was significant with lowest AA contents identified in T1 at the

end of storage period (Fig. 75).

Reduction in ascorbic acid was rapid and steady in control and integrated

treatment respectively. The ultimate percentage decline in AA contents was 41.1%

in T1 on 80th day while 13.8% decline observed in T2 during the same storage

period. Percentage decline in AA contents in integrated treatments remained steady

(23.68%) till 140th day storage there after showed significant eventual decline

(35.28%) at the end of storage period.

Fruits and vegetables are the rich source of dietary anti oxidant vitamin i.e.

ascorbic acid which has vital significance in human metabolism during collagen

formation and immune stimulation (Dale et al., 2003). Owing to its susceptibility

to light and heat the assured presence of this anti oxidant during post harvest

storage is of principal importance (Larisch et al., 1996). Ascorbic acid decline in

both treatments showed that decrease was not only the function of storage

conditions but also due to storage time. Prominent AA contents decline in control

might be attributed to the rapid oxidation of ascorbic acid into dehydro-ascorbic

acid (Blenkinsop et al., 2002) and accelerated due to increased weight loss at

ambient temperature. Intergrated treatment retained appreciable AA contents

during most of the storage period as compare to control. The maximum retention

of ascorbic acid contents might be attributed to modified atmosphere packaging

during the storage period which conferred barrier properties to gaseous exchange

271

14

16

18

20

22

24

26

1 20 40 60 80 100 120 140 160 180


Asc

orb

ic a

cid

(m

g/10

0g)

T1 (Control)

T2 (Treatment)

Fig. 75 Ascorbic acid in response to integrated treatment maintaining higher contents as compare to control during storage

(LSD (0.05) for treatment= 0.1082 LSD (0.05) for interval= 0.2420 LSD (0.05) for interaction= 0.3422)


272

resulted in limited oxidation of ascorbic acid as also reported by Conte et al.,

(2009). In addition temperature management in integrated treatment slowed down

the cellular metabolism consequently retained substantial AA contents during

storage. Similar results regarding higher retention of ascorbic acid at lower

temperature were reported by Nourian et al. (2003), Rivero et al. (2003) and

Davies et al. (2002).


General trend was increase in chlorophyll contents with the increase in

storage period in both treatments. Treatment means illustrated higher chlorophyll

contents in T1 as compare to T2 during storage. Storage intervals means

demonstrated significant difference in their chlorophyll contents with maximum

value quantified on 180th day. The interaction between treatments and storage

intervals was significant with lowest contents estimated at the start of storage in

both treatments while highest contents observed in T1 at the end of storage period

(Fig. 76).

Chlorophyll contents continued to increase in both treatments during

storage. The increase was significant in control on 40th day onward with 3-folds

increase estimated at the end of storage. Increase in chlorophyll contents remained

non significant in integrated treatment during initial 60 days there after showed

slow increase till the end of storage period. The notable increase observed in

integrated treatment was 2-folds, 2.5-folds and 2.7-folds on 140th, 160th and 180th

days respectively.

Post harvest potato greening is an important phenomenon associated with

the concomitant increase of chlorophyll during storage. Green colored tubers

generally perceived as low quality products due to greening, discoloration and

273

0.4

0.8

1.2

1.6

2

1 20 40 60 80 100 120 140 160 180


Ch

loro

ph

yll (

mg/

100g

d.w

T1 (Control)

T2 (Treatment)

Fig. 76 Chlorophyll in response to integrated treatment maintaining lower contents as compare to control during storage



274

increased incidence of glycoalkaloid contents (Nema et al., 2008). Results

expressed in present study concluded that integrated treatments accumulated lower

chlorophyll contents as compare to control consequently presented less tuber

discoloration. Dark potato storage supplemented with modified atmosphere

packaging (Rosenfield et al., 1995) suitable temperature management (Nourian et

al., 2003) and appropriate sprout inhibition ((Kleinkopf et al., 2003) found

valuable in efficient potato storage for six months. Increased chlorophyll contents

with subsequent discoloration in control reduced the over all tuber quality which

confirmed the results presented by Rita et al. (2007) Grunenfelder et al. (2006) and

Percival, (1999).

4.6.9 Effect of integrated treatment on Total Glycoalkaloids

Total glycoalkaloids (TGA) in general showed gradual increase in both

treatments with the progress in storage duration. Treatment means illustrated

significant difference between them with T1 accumulated higher TGA contents.

Non significant difference was observed between 60th and 140th days while all

other Storage interval remained statistically different at α-0.05. The interaction

between treatments and storage intervals was significant with maximum TGA

contents quantified in T1 on 80th day (Fig. 77).

TGA contents increased in both treatments with higher accumulation

estimated in control than the integrated treatment. The initial increase estimated in

TGA contents was around 2-folds on 20th day storage and remained relentless with

eventual more than 12-folds increase estimated on 80th day storage. The final TGA

contents quantified (86.23 mg/100g D.W) in control potato exceeded the safe limit

prescribed for human intake.

275

0

20

40

60

80

100

1 20 40 60 80 100 120 140 160 180


TG

A (

mg/

100g

d.w

)

T1 (Control)

T2 (Treatment)

Fig. 77 Total Glycoalkaloids in response to integrated treatment maintaining lower contents as compare to control during storage

(LSD (0.05) for treatment= 0.689 LSD (0.05) for interval = 1.492 LSD (0.05) for interaction = 2.111)


276

Integrated treatment retained moderate TGA contents during most of the storage

period with eventual 7-folds increase on 180th day. In comparison TGA contents

quantified in control on 60th day were higher than that estimated in integrated

treatment at the end of six month storage.

Increased world over consumption of potato focused the attention of

researchers regarding the presence of its toxic glycoalkaloids. Small amount of

TGA contents in potato reported to improve flavor however their increased level

above 28mg/100g f.w can bring about possible lethal consequences (Nema et al.,

2008). Post harvest storage of potato is usually accompanied with the simultaneous

increase in TGA contents during storage as also observed in the present study.

Biosynthesis of TGA is independent however known to be associated with tuber

sweetening (Percival, 1993), greening (Rita et al., 2007) and sprouting (Sengul et

al., 2004). Integrated treatments retained lower TGA accumulation and improved

storage stability as compare to control owing to their improved packaging system,

apt storage temperature with apposite anti sprouting agents which was in line with

the findings of researchers like Rosenfeld et al. (1995) and Nema et al. (2008),


General trend was initial increase in total phenolic contents (TPC) followed

by gradual decline with the increase in storage period. Treatment means

demonstrated that T2 retained higher TPC as compare to T1. Storage interval means

showed significant difference between them with highest TPC estimated on 20th

and 100th days with non significant difference found in between them. The

interaction between treatments and storage intervals was found significant with

maximum TPC observed in T2 on 80th day (Fig. 78).

277

TPC increased in control till the mid storage afterward showed progressive

decline till the end. The percentage increase and decrease in TPC in control

remained around 40% and 32% respectively during 80 days storage. TPC

continued to increase in integrated treatment till 80th day there after showed decline

till the rest of storage period. The percentage increase and decrease in TPC in

integrated treatments remained about 50% and 13% respectively during 180 days

of storage. In comparison the maximum TPC quantified in control on 40th day

remained statistically similar to those observed in integrated treatment on 100th day

storage.

Total phenolic contents are one of the most commonly occurring

bioactive plant secondary metabolite synthesized during shikimate and acetate

pathways (Bravo, 1998). They are amongst the major antioxidants reportedly

present in potato along with ascorbic acids, carotenoids, tocopherols etc.

(Reyes and Zevallos, 2003). Despite of carrying modest TPC contents potato

showed significant inhibition of low density lipoprotein oxidation (Vinson et

al., 1998). Phenolic contents known to increase during the post harvest

storage of potato however found susceptible to the activities of enzymes like

polyphenol oxidases and peroxidase (Vitti et al., 2011). Our results showed

that integrated treatments retained appreciable TPC during most of the storage

period as compare to control. Modified atmosphere packaging along with low

temperature storage prevented the oxidative degradation of TPC during

storage. Maintaining tuber dormancy as results of different anti sprouting

agents also kept tubers out of physiological stress imposed by polyphenol

oxidases thus retained appreciable TPC as compare to control.

278

60

80

100

120

140

160

180

1 20 40 60 80 100 120 140 160 180


TP

C (

mg

GA

E/1

00g

d.w

T1 (Control)

T2 (Treatment)

Fig. 78 Total phenolic contents in response to integrated treatment maintaining higher contents as compare to control during storage (LSD (0.05) for treatment= 1.918 LSD (0.05) for interval= 3.795 LSD (0.05) for interaction= 5.368)


279

The results expressed are in line with the observations reported by

Madiwale et al. (2011), Barberan and Espin, (2001) and Saltveit, (2000)

regarding the post harvest stability of Total Phenolic Contents under improved

storage conditions.


In general radical scavenging activity (RSA) showed initial increase

followed by gradual decrease in both treatments with the progression in

storage period. Treatment means illustrated significant difference between

them with higher activity estimated in T2 as compare to T1. Storage interval

means showed significant difference between them with maximum activity

quantified in T2 on 100th day. The interaction between treatments and

storage intervals was significant with T2 retained utmost activity during most

of the storage period with lowest activity estimated in T1 at the end of

storage (Fig. 79).

Increase in radical scavenging activity remained statistically

significant in both treatments on 20th day storage. RSA significantly

decreased afterward on 80th day in control expressing 50% decline from the

terminal value (41.50%) estimated during the storage. Integrated treatments

retained appreciable RSA during most of the storage period. The activity

continued to increase on 60th day (45.73%) and remained statistically same

onward till 100th day (44.47%) storage. Progressive decline in RSA observed

afterward with minimum value estimated at the end (23.50%).

280

15

20

25

30

35

40

45

50

1 20 40 60 80 100 120 140 160 180


RSA

(%

)

T1 (Control)

T2 (Treatment)

Fig. 79 Radical scavenging activity in response to integrated treatment maintaining higher activity as compare to control during storage (LSD (0.05) for treatment= 0.462 LSD (0.05) for interval= 1.025 LSD (0.05) for interaction= 1.449)


281

Radical scavenging activity in potato tubers corresponds to their antioxidant

potential. Anti oxidant compounds present either as enzymatic or non-

enzymatic known to inhibit substrate oxidation and quench free radical

produced in biological system (Arnao, 2000). Enzymatic and non-enzymatic

antioxidants are required for intracellular and extracellular defenses against

different oxidants produced during cellular metabolism.

The radical scavenging activity estimated in the present study is

primarily related to the non-enzymatic anti oxidants. Retention of significant

antioxidant potential in potato thus required for its storage stability and

valuable functional potential. The increased activity during the initial

storage period in potato tubers might be attributed to their high ascorbic

acids and phenolics contents (Blessington et al., 2007). The significant

correlation between radical scavenging activity and phenolic compounds has

been reported by different researchers like Abbasi et al. (2011) and Lachman

et al. (2008).

Integrated treatment retained appreciable antioxidant activity during

most of the storage period as compare to control. The increased activity

under modified atmosphere storage (Piga et al., 2002), appropriate storage

temperature (Lewis et al., 1999) in the presence of suitable sprout inhibitors

(Bajji et al., 2007) has been reported by several researchers which verified

the facts framed in the present study. Eventual decline in activity might be

attributed to the loss of ascorbic acids along with increased polyphenol

oxidase activity under prolonged storage as observed by Davies et al.

(2002).

282

4.6.12 Effect on Polyphenol Oxidase (PPO) Activity

Polyphenol activity (PPO) in response to integrated treatments (T2) retained

lower PPO activity during storage in contrast significant activity was observed in

control (T1) (Fig. 80). Treatment means showed lower PPO activity in integrated

treatment and higher in control during storage. Storage interval means showed

significant difference in their PPO activity with maximum activity observed on

80th day. Non significant difference observed between 1st, 20th and 180th days

during the storage period. The interaction between treatment and storage intervals

was highly significant with maximum value recorded in T1 on 80th day (Fig. 80).

PPO activity increased in control with the progression in storage period.

The activity remained steady till 20th day there after increased progressively upto

80th day. The PPO activity in control was not estimated afterward because of

excessive sprouting due to dormancy break. The over all increase in PPO activity

remained around 2.5 folds than that estimated on the 1st day of storage. In contrast

significant decline in PPO activity was illustrated by integrated treatments.

Percentage decline in PPO remained highest on 20th day (23.6%) afterward

increased steadily till remained below the activity (30.47 U/g) observed in the start

of experiment.

Polyphenol oxidases are the metalloenzymes which catalyzes oxidation of

phenols into quinines and subsequent brown colored melanin formation (Afify et

al., 2012). The enzymes are associated with plant response under different stress

conditions and taken as an index of post harvest life in horticultural commodities.

High PPO activity observed in control might be associated with the tuber sprouting

283

20

30

40

50

60

70

80

1 20 40 60 80 100 120 140 160 180


PP

O (

U/g

f.w

)

T1 (Control)

T2 (Treatment)

Fig. 80 Polyphenol oxidase in response to integrated treatment showing lower enzymatic activity as compare to control during storage (LSD (0.05) for treatment = 0.347 LSD (0.05) for interval = 0.776 LSD (0.05) for interaction = 1.097)


284

and physiological stress imposed due to senescence (Byrant, 2004). Integrated

post harvest management of potato tubers under storage retained lower PPO

activity even after 180 days storage. Application of hot water treatment was

found effective in the partial inactivation of this enzymes as also been observed

by Yemenicioglu, (2002). The application of improved packaging materials i.e.

polypropylene (Kader, 2002), appropriate temperature management i.e. 10oC

(Nourian et al., 2003), suitable sprout inhibitors i.e. Clove oil (Arif et al., 2010)

maintained low PPO activity consequently presented prolonged storage stability

(180 days) of potato tuber as compare to control (80 days).

4.6.13 Effect on PerOxidase (POD) activity

In response to the application of integrated treatment (T2) POD activity

decreased in potato tubers while parallel increase was observed in control (T1).

Treatment means showed significant difference between them with T1 retained

higher POD activity than T2. Storage interval means exhibited significant

difference in their POD activity with maximum value estimated on 80th day. The

interaction between treatments and storage interval was significant with

maximum value identified in T1 during most of their storage period (Fig. 81).

POD activity continued to increase in control with no sign of termination

till the on set of sprouting at the end of storage. The significant increase in POD

activity witnessed on 40th day (21.17 U/100g) storage onward and ended with

more than 3-folds increase on the 80th day (77.03U/100g). POD activity declined

significantly in response to integrated treatment applied through out the storage

period. Like poly phenol oxidase activity decline in per oxidase activity also

observed till 80th day storage (9.10 U/100g) there after showed moderate rise till

285

8

16

24

32

40

1 20 40 60 80 100 120 140 160 180


PO

D (

U/1

00g

f.w

)

T1 (Control)

T2 (Treatment)

Fig. 81 Per oxidase in response to integrated treatment showing lower enzymatic activity as compare to control during storage (LSD (0.05) for treatment= 0.2054 LSD (0.05) for interval = 0.4594 LSD (0.05) for interaction = 0.6497)


286

180th day (11.40 U/100g). The final POD activity remained below the value

estimated before the start of experiment on 1st day.

Peroxidases (POD) and polyphenol oxidases (PPO) are considered as the

major enzymes responsible for quality loss in potato due to phenol degradation

(Francois and Espin, 2001). The estimation of these enzymes during post harvest

storage of horticultural produce presents reasonable assumption for their eventual

storage stability. The decrease in POD activity in integrated treatments might be

attributed to the lower temperature storage (10oC) as compare to control. In

addition the application of polypropylene packaging with clove oil application

conferred barrier properties with sprout inhibition eventually maintained tuber

dormancy up to 180 days as compare to 80 days observed in control. The efficient

storage stability of potato tubers under different integrated post harvest treatments

is also reported by researchers like Nourian et al. (2003), Delaplace et al. (2010)

and Afify et al. (2012).

4.6.14 Effect on Chip Moisture Contents

In general pre processing application of different concentrations of Aloe

Vera (A.V) on the potato chip showed increase in Chip Moisture Contents.

Treatment means showed significant difference between them with maximum

CMC observed in T4 and minimum in T1. Storage interval means showed

significant difference between them with maximum CMC estimated on 180th day.

The interaction between treatments and storage intervals was found significant

with maximum CMC quantified in T4 at the end of storage period (Fig. 82). CMC

increased with the increase in the concentration of A.V coatings during the storage

period.

287

0

3

6

9

12

15

1 30 60 90 120 150 180


Ch

ip m

oist

ure

con

ten

t (%

)

Control

A.V 10%

A.V 20%

A.V 30%

Fig. 82 Higher Chip moisture content in potato chips due to aloe vera (A.V) coatings as compare to control



288

The increase in CMC in A.V 10%, A.V 20% and A.V 30% remained around 8.1

folds, 9-folds and 11.1-folds after 180 days storage. In contrast the increase in

control remained less than 2-folds during the same storage period.

Pre processing chip moisture contents is directly proportional to the post

processing fat absorption. Surface properties of frying raw material are very

important to establish eventual fat absorbed during processing. Modification in

these surface coatings may be carried out by the application of different edible

coating which can be transparent or thick like batter (Mellema, 2003). In doing so

uniform coating configuration on the surface is imperative to bound mass transfer

during processing (Huse et al., 1998). Garmakhany et al. (2008) also evaluated

quality attributes of potato chips in response to different hydrocolloid

applications.

Different coating materials i.e. carboxy methyl cellulose, xanthan, and

guar were applied in selected concentrations before processing. He concluded all

the coating materials retained comparatively high moisture contents and reduced

fat absorption as compare to control. Our results showed that increasing A.V

concentration resulted in increased CMC after processing with similar pattern

observed with the progression in storage period. Similar observations were

reported by Khalil, (1999) regarding the increased moisture contents in French

fries in response to increased coating concentration. The appropriate

concentration of coating material however must be established in order to prevent

sogginess and reduced sensorial scores as happened in T4 (A.V 30%) during the

last month of storage.

289


Chip fat absorption (CFA) decreased with the progression in storage

period in all the treatments except in control. Treatments means revealed

significant difference between them with maximum and minimum CFA estimated

in T1 and T4 respectively. Non significant difference observed between 30th and

60th days while all other storage intervals differed significantly with each other.

The interaction between treatment and storage interval was significant with

maximum CFA estimated in T4 during most of the storage period (Fig. 83).

Amongst different treatments concentrations of Aloe vera showed significant

reduction in CFA along the storage period. The percentage reduction in CFA on

20th day remained around 13.4%, 20.5% and 23.1% in T2 (A.V 10%), T3 (A.V

20%), and T4 (AV 30%) respectively in contrast slight increase in CFA observed

in control. With in different storage intervals CFA increased amongst all the

treatments with lowest CFA observed in T4 (27.53%) followed by T3 (27.98%)

while maximum CFA estimated in T1 (37.00 %) on 180th day storage.

Potato chip is preferred snack food liked all over the world due to its

unique sensorial attributes. The intake of this quality food product is how ever

associated with high fat intake thus largely contributing towards obesity and

coronary heart disorders (Mellema, 2003). In addition to different techniques

employed to reduce eventual fat absorption hydrocolloids application has been

carried out by different researchers to reduce the fat absorption in processed food

products. The efficiency of these coating materials however depends on their

barrier properties, applied concentration and ability to produce quality finished

290

20

25

30

35

40

1 30 60 90 120 150 180


Chip

fat

abso

rpti

on (

%)

Control

A.V 10%

A.V 20%

A.V 30%

Fig. 83 Higher Chip fat absorption in potato chips due to aloe vera (A.V) coatings as compare to control



291

products (Garcia et al., 2002). Our results in the present study showed fat

reduction in processed products in response to different coating concentrations

applied which confirmed the previously reported findings by Rimac-Brncic et al.,

(2004), Albert and Mittal, (2002) and Rayner et al. (2000). The significant

increase in CFA along the storage intervals in different treatments might be

associated with starch degradation which has also been reported by Basuny et al.

(2009), and Kita, (2002).

4.6.16 Effect on Chip Color (CCL)

Chip color estimated as approximate L-value generally decreased with the

increase in storage duration. Non significant difference observed between T2 and

T3 regarding their CCL values with maximum and minimum value estimated in

T1 and T4 respectively. Significant difference between most of the storage

intervals observed with highest and lowest values were estimated at the start and

the end of storage period respectively. Interaction between treatments and storage

intervals was significant with minimum values quantified in T4 during last month

storage (Fig. 84).

L-value decreased in all the treatments with the increase in storage period

with statistically similar value recorded during most of the storage period.

Maximum color values were identified in control during most of the storage

period with lowest percentage decrease (6.1%) estimated on 180th day storage. In

contrast the percentage decrease in L- value remained higher in coated chips with

utmost decline observed in T4 (10.7%) during the same storage time. In terms of

L-value, T2 and T3 remained statistically similar through out the storage period

with 8.7% decline observed in each treatment till the end of storage period.

292

56

58

60

62

64

66

1 30 60 90 120 150 180


Col

or (L

-val

ue)

Control

A.V 10%

A.V 20%

A.V 30%

Fig. 84 Comparision of Chip color in response to aloe vera (A.V) coatings on potato chips (LSD (0.05) for treatment = 0.910 LSD (0.05) for interval = 0.425 LSD (0.05) for interaction = 2.408)


293

L-values correspond to the lightness of chip color which is primarily

associated with the consumer acceptance (Mendoza et al., 2007). In the present

study CCL values affected by different coating applications and decreased with

the increase in the applied concentrations. For instance chips coated with 10 %

A.V (T2) and 20% A.V (T3) retained high L-values than those coated with 30%

A.V (T4) coating. Similar results were reported by Khalil, (1999) who reported

decreased color values in French fried due to calcium chloride application at

increased concentration. Our results revealed that increase in A.V concentration

maintained appreciable L-value up to some threshold level (10-20%) however

exhibited considerable decline (30%) as a consequence of excess application as

also reported by the researcher above. Coating application prior to frying in

potato products has been reported to decrease likely acrylamide formation in

processed products (Fiselier et al., 2004).

In the present study retention of appreciable CCL scores as results of

different coating (A.V-10%, A.V-20%) might also be associated with their

reduced acrylamide formation. Similar observation regarding reduction of

acrylamide contents as results of pre processing coating applications has been

reported by Vattem and Shetty (2003). The steady decline in L-values in all the

treatments along storage period might be attributed to their increased reducing

sugar contents as also been observed by Biedermann-Brem et al. (2003) and

Blenkinsop et al. (2002).


Chip crispiness scores showed initial increase till the mid storage

followed by gradual decline at the end. Treatment means showed significant

difference between their CCR scores with maximum estimated in T3 followed by

T2. Non significant difference was observed between 30th and 120th days while all

other intervals were significantly different at 5% level of significance.

294

3

3.5

4

4.5

5

1 30 60 90 120 150 180


Ch

ip c

risp

ines

s (s

core

s)

Control

A.V 10%

A.V 20%

A.V 30%

Fig. 85 Comparision of Chip crispiness in response to aloe vera (A.V) coatings on potato chips (LSD (0.05) for treatment = 0.0677 LSD (0.05) for interval = 0.0896 LSD (0.05) for interaction = 0.1792)


295

The interaction between treatments and storage intervals was significant with

maximum CCR scores quantified in T3 during most of the storage period (Fig.

85). Remarkable CCR scores were identified in low and moderate A.V coatings

during the storage period. Aloe Vera at 20% concentration presented best CCR

scores through out the storage period however remained statistically similar to

10% application during most of the storage period. Significant decline in CCR

scores was observed in 30% application during the last month of storage period.

Crispy texture is the hallmark attribute of potato chips which is believed

to be associated with the dry matter present in raw material. Starch and

protopectin are the most imperative chemical component contributing to quality

chip texture (Kita, 2002). Textural attributes reported to be effected by the

application of different coatings due to modification of surface properties

(Mellema, 2003). Application of 20% Aloe vera presented remarkable chip

texture during frying while inferior CCR scores were quantified in Aloe vera

30% which might be due to their increased moisture retention which

subsequently caused sogginess after processing (Pedreschi and Mayano, 2005).

Superior maintenance of textural attributes with acceptable scores due to

hydrocolloid coating have also been reported by researchers like Khalil (1999),

Kita, (2002) and Garcia et al. (2002).


Chip flavor scores in general illustrated gradual initial increase followed

by decline at the end of storage period. Treatment means showed significant

difference between their CFL scores with maximum CFL scores observed in T1.

followed by T3. Non significant difference observed between most of the storage

intervals with lowest CFL scores estimated on 180th day. Interaction between

296

3

3.5

4

4.5

5

1 30 60 90 120 150 180


Chip

fla

vor

(sco

res)

Control

A.V 10%

A.V 20%

A.V 30%

Fig. 86 Comparision of Chipflavor in response to aloe vera (A.V) coatings on potato chips



297

treatments and storage interval was significant with lowest scores identified in T4

at the end of storage period (Fig. 86). Significant decline in CFL scores was

observed in T4 (A.V 30%) after mid storage period with minimum scores

(3.10/5.00) identified on 180th day. T2 (A.V 10%) and T3 (A.V 20%) maintained

appreciable flavor scores during most of the storage period with 3.64/5.00 and

3.78/5.00 CFL scores respectively estimated at the end of storage. Control

retained maximum flavor scores through out the storage period with 4.04/5.00

CFL scores identified at the end of storage period.

Flavor is the combined sensation derived from the senses of taste and

aroma. In general hydrocolloid coatings presented lower CFL scores as compare

to control. Maximum CFL scores were estimated in control during most of the

storage period which might be attributed to their high fat absorption during

processing. Frying oil importance as flavor precursor has also been reported by

Martin and Ames, (2001). Garcia et al. (2002) evaluated the efficiency of

different cellulose based edible coatings in reduction in oil absorption during

processing. He concluded that the combination of 1% methyl cellulose and 0.5%

sorbitol proved to be most efficient coating for fat reduction and flavor retention

in potato chips. In the present study Aloe vera coatings except in 30% application

presented appreciable CFL scores during chip processing which also of great

significance because of no coating based off flavor development identified by the

judges during evaluation. A.V (30%) presented lowest flavor scores due to bitter

after taste and increased moisture contents in processed chips. It was eventually

concluded that A.V (20%) retained all the chip sensorial attributes owing to its no

after taste and off flavor development along with lowest chip fat absorption.

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GENERAL DISCUSSION

Potato is a delicious, highly nutritive vegetable extensively being consumed

all over the world in variety of food preparations. Presence of low cholesterol and

significant ascorbic acids and phenolic contents confer momentous funtional

potential to this vegetable. The crop is however facing different physiological

disorders like greening, alkaloidal toxicity, cold sweetening and sprouting during

its post harvest storage. In addition acrylamide formation in thermally processed

potato products is of grave food safety concern. The study was therefore designed

to optimize different storage conditions (packaging, light, temperature, sprout

inhibitor) to ensure regular supply of premium potato variety for the local potato

industry with the use of cheap, natural and safe technologies.

In the first phase of the study “Lady Rosetta” presented best overall

characteristics amongst the tested varieties due to its suitable size and sphericity,

low sprout (%), high dry matter, low fats and reducing sugar contents, significant

functional potential and above all the remarkable processing performance. Atlantic

and Hermes were also impressive owing to their high dry matter contents, long

dormancy period and impressive processing performance however outstanding

functional potential has been identified in the Desi variety. The study also invoked

significant correlations between different quality attributes studied in the selected

potato varieties (Table 2b, 4b).

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299

In order to optimize the storage conditions for the premium potato variety

the second phase of the study was divided into four different experiments to

evaluate the effect of different packagings, light sources, temperature regimes and

sprout inhibitors on the selected quality attributes. In general weight loss, total

soluble solids, glucose, total sugars, glycoalkaloids, chlorophyll, polyphenol

oxidase, peroxidase, increased while pH, specific gravity, starch and ascorbic acids

decreased with the progression in storage period. Total phenolic contents and

radical scavenging activity showed a sort of parabolic trend during the storage

period. Post processing parameters like chip moisture contents, chip fat absorption

increased while sensorial attribute exhibited gradual decrease along the storage

period. In spite of this general trend, significant divergences were observed with in

different treatments and storage conditions in the studied quality attributes.

Weight loss (%) was found maximum in control however the use of poly

propylene and LDPE packaging, dark potato storage and application of essential

oils as sprout inhibitors proved to be vital tool in preventing potato dehydration

during storage. Temperature management below 15 oC presented minimum weight

loss (%) amongst all the storage conditions studied which might be due to the

reduced respiration rate at low temperature (Kyriacou et al., 2009). Total soluble

solids (TSS) increased during the storage period due to hydrolytic conversion of

starch in to soluble sugars (Kittur et al., 2001). Packaging like polypropylene and

LDPE, dark storage and sprout inhibitors maintained slower increase in total

soluble solids as compare to control. Low temperature storage provoked significant

increase in the TSS contents which might be mediated due to the phenomenon of

300

cold sweetening. The final decrease in TSS was also found associated with potato

sprouting (%) due to the rapid utilization of soluble sugars by growing sprouts as

also reported by Sowokinose, (1990).

Significant correlation was reported between specific gravity and starch

contents of potato by several researchers (Kazami et al., 2000, Kumar et al., 2004)

which remained consistent in the present study under different storage conditions.

After initial increase in the specific gravity and starch contents during early week

of storage the attributes started to decline during storage period. Polypropylene and

LDPE packaging, dark storage and application of sprout inhibitors caused this

decline at slower pace as compare to their respective controls. Starch degradation

at the twilight of the storage was also found closely associated with the appearance

of visible sprouts (Farre et al., 2001). Conversely highly prominent decline was

observed during the early week in these two parameters under low temperature

storage (5 oC).

Predominant sugars produced in the potato are sucrose, glucose and fructose

(Hajirezaei et al., 2003) and showed diverse sugar metabolism specifically under

comparative temperature storage. Packaging like LDPE, polypropylene maintained

controlled sugar accumulation in potato as compare to control. Similar

observations were recorded in response to the different sprout inhibitors and dark

potato storage. Considerable increase in sugar contents were recorded at high

temperature as well as low temperature storage. Storage at 25 oC resulted in the

increase in sugar contents from starch degradation due to senescence sweetening.

301

On the other hand the storage at 5 oC triggered significant sugar accumulation due

to the phenomenon of cold sweetening (Tamaki et al., 2003). The study showed

that variety Lady Rosetta was cold susceptible variety and require some critical

storage temperature to avert potato sweetening under prolong storage.

Tuber toxicity due to the presence of total glycoalkaloids (TGA) contents in

potato was also studied under different storage conditions. TGA contents continued

to increase under all storage conditions however the increase was found

proportional to the weight loss (%), high energy light sources, tuber sprouting

(Nema et al., 2008) and high temperature storage. Minimum TGA contents were

identified in packaging, dark storage, low temperature storage and essential oil

applications. Study also revealed high significant correlation between TGA

contents and chlorophyll accumulation in response to exposure to high energy

illuminations like red and blue lights (Table 31, 32).

Ascorbic acid is the predominant organic acid in potato tuber which also

corresponds to its significant radical scavenging activity under DPPH assay

(Nzaramba, 2007). Post harvest profile of potato tuber revealed significant

reduction in ascorbic acid in response to high energy light sources, heat, increased

weight loss (%) and sprouting. Improved packaging like LDPE and polypropylene

retained substantial ascorbic acid contents as compare to control which has also

been reported by (Calderon et al., 2008). Storage at low temperature (5 oC)

retained maximum ascorbic acid during the four month storage however found

detest due to the rapid increase in sugar contents.

302

LDPE and polypropylene packaging retained significant total phenolic

contents (Gonzalez et al., 2004) as compare to control. Over all TPC continued to

increase under different storage conditions followed by gradual decline afterward.

The possible reason might be due to the onset of potato browning and sprouting

during the final weeks of storage. On the other hand low temperature (5 oC)

Storage retained maximum TPC during storage period (Lachman et al., 2008).

RSA corresponds to total phenolic contents and ascorbic acid contents present in

the potato tubers. Improved packaging, dark storage, sprout inhibitors and low

temperature storage also maintained appreciable RSA activity as compare to their

respective controls. Highly significant correlation was identified between TPC and

radical scavenging activity (RSA) during the start of potato storage which

decreased after ward due to the loss of ascorbic acid during storage.

PPO and POD continued to decrease under all storage conditions however

the activity of former was found highly prominent during potato post harvest

storage. Packaging reduced the enzymatic activity as compare to control possibly

might be due to substrate inhibition and low phenolic oxidation (Kader, 2002).

Significant reduction in PPO and POD activities were observed at low temperature

(5 oC) storage. PPO activity was found susceptible to potato blanching during hot

water treatment carried out as sprout control while POD activity remained un

deterred which confirmed the findings reported by Yemenicioglu, (2002).

Post processing evaluation of potato chips showed significant association

between chip quality and the composition of potato tubers under different storage

303

conditions. Chip moisture content and chip fat absorption were inversely related

with the specific gravity and starch contents of the raw material as reported by

Mehta and Swinburn, (2001). Chip color and chip texture were found closely

related with the presence of sugar and starch contents respectively (Kita, 2002).

Potato storage at low temperature (5 oC) presented prominent decline in color

scores which might be associated with elevated reducing sugar contents due to cold

sweetening. Polypropylene packaging and potato storage at 15 oC presented

remarkable processed products as compare to control.

In the last phase (3rd phase) of the study the prominent results identified

during different storage conditions were offered in combination to develop an

integrated strategy to conserve these vital quality attributes during the storage. The

strategy comprised of the best packaging material (polypropylene), suitable light

source (dark), optimum storage temperature (10 oC) and appropriate sprout

inhibitors (hot water treatment followed by clove oil application) to access the

storage life with intact quality parameters. Post harvest disorders like alkaloidal

toxicity, cold sweetening, greening, sprouting in potato were efficiently controlled

with out posing any health or environmental hazards. Results showed the

conservation of vital quality attributes and post harvest storage life of potato

variety “Lady Rosetta” was prolonged up to three times as compare to control.

This phase was distinguished with the application of different levels of Aloe vera

prior to potato processing with an objective to produce low caloric HALAL

(permissible food in Islamic jurisprudence) potato product. High chip moisture

contents, appreciable sensorial scores and reduced chip fat absorption were

304

observed as result of different levels of hydro colloidal coatings before processing.

Moreover Aloe vera coating produced potato chip with remarkable color scores

which can also be associated with low perceived acrylamide formation as also been

reported by other researchers like Vattem and Shetty, (2003) and Fiselier et al.

(2004). 20% Aloe vera application proved to be the best vegetable based potato

chip coating with moderate moisture and fat contents and appreciable retention of

sensorial score.

305

CONCLUSIVE SUMMARY

Potato is third major staple crop after wheat and rice with increasing total

production witnessed over the last twenty years in developed and under developed

countries. In addition to its table use substantial increase in the consumption of

versatile processed potato products such as, chips, mashed potatoes, baked potato,

tinned potatoes etc. have been observed all around the world. Recognizing the

global importance of this crop with special reference to food security issue in the

third world and densely populated countries, FAO had declared year “2008” as an

International Year of Potato (IYP).

Potato is the premium vegetable crop of Pakistan grown through out the

country with four growing seasons. The bulk of produce however is wasted due to

Poor post harvest management practices results in post harvest storage disorders

like greening, cold induced sweetening, steroidal toxicity, sprouting etc. In

addition limited availability of quality raw material for processing is the main

concerns for the industry. Sighting the above reported problems three-phased

comprehensive study was planned to establish integrated approach for the

prevention of post harvest losses along with intact quality processing attributes in

premium potato variety during storage.

In the 1st phase of study ten commercial potato varieties namely, Agria,

Atlantic, Cardinal, Courage, Chipsona, Desiree, Desi, Hermes, Lady Rosetta and

Satellite were studied for their physical, chemical and functional attributes, with

special reference to their potential in chip processing. In general Lady Rosetta

followed by Hermes was the most appreciable variety regarding their physical

305

306

attributes. Lady Rosetta followed by Atlantic attained maximum dry matter and

starch contents. However, least sugar contents were recorded in Agria and

maximum fat and protein contents were found in Desiree. Significant correlation

(R= 0.986) was estimated between dry matter and starch contents. Amongst tested

varieties Agria, Desiree and Hermes were preferred for their mineral contents and

are positively correlated (R= 0.898) with their ash contents. In general; functional

attributes were found maximum in Desi followed by Desiree. A promising

correlation was reported amongst most of these parameters with distinctive

correlation (R=0.953) identified between total phenolic contents and radical

scavenging activity. Post processing parameters like moisture contents, fat

absorption, and sensory evaluation in Lady Rosetta showed its preference over all

other varieties followed by Hermes.

The 2nd phase of the study was divided into four different experiments in

order to identify best packaging material for storage and transit, suitable light

source for retail display, appropriate storage temperature and suitable anti

sprouting agent. Application of suitable packaging systems extends the storage life

by slowing down the respiration rate, protecting them during transit, and conferring

value addition during marketing. As 1st experiment of second phase of study the

efficiency of different packaging materials like jute, nylon, polypropylene, cotton,

low density polyethylene, medium density polyethylene and high density

polyethylene were studied along with control on the premium potato variety “Lady

Rosetta” (selected in the first phase). After harvest potato tubers were washed,

sorted, graded, cured and than placed in different packaging materials at ambient

storage maintained at 25± 2oC. The transition in quality attributes of potato tubers

307

under different packaging materials were studied on the basis of their physico-

chemical, functional and processing parameters. In general weight loss, total

soluble solids, glucose, total sugars, glycoalkaloids, polyphenol oxidase,

peroxidase, chip moisture contents, chip fat absorption increased with the

progression in storage period. Parameters like pH, specific gravity, starch, ascorbic

acids, chip color, chip crispiness and chip flavor decreased with the increase in

storage. Total phenolic contents and radical scavenging activity showed initial

increase followed by decline during increasing storage period. Amongst different

packaging employed potato stored in polypropylene and low density polyethylene

packaging presented best over all retention of vital quality attributes during 63

days storage however, tensile strength of polypropylene packaging made it

advantageous for prolonged potato storage with easy transit operations during

marketing.

Retail display of potato tubers are carried out in super markets under

additional light sources to impart aesthetic value and consumer’s attention however

is associated with potato greening. The objective of second experiment of 2nd phase

was to identify most appropriate light source for best potato variety “Lady Rosetta”

with appreciable retention of different quality parameters. Potato tubers were

placed for 27 days at ambient storage (25± 2oC) under different light sources i.e.

blue, fluorescent, green, mercury and red along with dark storage which also

served as normal control. The results showed maximum retention of different

quality attributes in dark potato storage. Amongst different light sources mercury

and green light retained appreciable retention of different quality parameters with

non significant difference estimated between them nevertheless green light

308

established its primacy due to superior processing performance and lower sugar

accumulation. Storage of potato under fluorescent, red and blue light proved to be

precarious due to skin discoloration, increased enzymatic activity and poor

processing performance. Over all results revealed tuber sensitivity to different

colored light along with the assessment of their storage stability.

Potatoes are usually stored under low temperature for sprout prevention and

to ensure their continuous supply when ever needed. Low temperature sweetening

is the principal temperature related disorder being faced by the growers in potato

during storage and is associated with critical storage temperature. The present

study aimed at identifying the appropriate storage temperature for the selected

potato variety with special reference to their quality attributes. Potato variety

“Lady Rosetta” was stored under different temperature regimes i.e. 5oC, 15oC and

25oC to identify most suitable storage temperature. Our results showed significant

variation in different quality attributes in response to different temperature studied.

Storage at 5oC maintained tuber dormancy for 126 days however associated with

increased sugar accumulation and rapid starch depletion during storage

consequently presented poor post processing performance. In contrast storage of

Potato tubers at 15oC retained lower sugar contents and superior processing

performance till the end of storage yet presented increased polyphenol oxidase and

peroxidase activities as compare to those stored at 5oC during the same storage

period. The storage stability of potato tubers at 25oC was significantly tested due to

dormancy break on 84rth day. Our results showed that potato variety “Lady

Rosetta” is cold sensitive and required critical storage temperature for premium

post processing performance.

309

Sprouting leads to increased fresh weight loss, elevated sugar contents,

high starch depletion and obstructs air movement under storage atmosphere. The

response of potato variety “Lady Rosetta” was evaluated against the application of

different anti sprouting agents in the fourth experiment of 2nd phase. Dormancy

break in potato tubers was considered complete at sprouting percentage of 25%

with sprout length of >3mm. The single application of different anti sprouting

agents like hot water treatment, spearmint oil, clove oil, and CIPC was carried out

to assess their effectiveness against tuber stability under storage. The tubers were

placed at ambient storage (25oC ±2oC) for 81 days to evaluate changes in physico-

chemical, functional, enzymatic and processing attributes of selected variety.

Results revealed significant response of variety “Lady Rosetta” to all anti sprouting

agents as compare to control. Highest retention of different quality attributes in

potato tubers were identified in CIPC application however mostly found

statistically similar to those estimated in clove oil application. Potato with clove oil

application retained appreciable total phenolic contents and exhibited higher anti

oxidant activity during storage period. Application of spear mint oil and hot water

treatment also proved to be useful in preventing potato sprouting as compare to

control however associated with increased weight loss at the end of storage period.

Post processing sensorial attributes showed the efficacy of all anti sprouting agents

with non significant difference estimated between most of them during storage.

Results showed that triumphant replacement of CIPC with essential oil might be

useful to avert related food safety and environmental issues and ensure organic

potato storage.

310

Integrated post harvest treatments were applied on potato variety “Lady

Rosetta” in the 3rd and last phase of the present study to asses the transition in their

quality attributes along with eventual storage life. Potato variety after preliminary

post harvest operations like sorting, grading, washing and curing treated with hot

water at 55±2oC for 15 minutes. After drying based on the results obtained in

experiment 1 and 2 of the present study potatoes were treated with clove oil (1%)

as anti sprouting agent, packed in polypropylene bags and than stored under dark at

10±1oC for subsequent quality attributes analysis. The results showed remarkable

storage performance of treated potato as compare to those placed under control.

The tubers maintained low weight loss, intact starch contents, low sugar and

glycoalkloids accumulation, during most of the storage period. Integrated treatment

retained appreciable functional potential with low enzymatic activity. Conclusively

tuber maintained their dormancy period for 180 days as compare to control tubers

sprouted on 80th day. In addition monthly pre processing application of different

concentrations of Aloe vera (10%, 20% and 30%) was carried out on potato chips

from integrated treatment to evaluate their processing performance. Though all the

potatoes produced quality product due to their effective post harvest storage

however hydro colloidal (Aloe vera) applications as coating material were found

effective in reducing oil uptake during processing. Steady increase in fat uptake

however observed with in the storage intervals along the storage period. Over all

Aloe vera 20% presented best results with reduced fat absorption and appreciable

chip sensorial attributes.

311

RECOMMENDATIONS

“Lady Rosetta” should be used as premium processing variety for potato

industry owing to its suitable size and sphericity, low sprout (%), high dry matter,

and reducing sugars, with over all remarkable processing performance.

Outstanding functional potential and other quality attributes identified in

the “Desi” variety should be the point of interest for potato breeders to develop

indigenous potato variety with considerable functional and processing quality

parameters.

Low Density polyethylene or polypropylene bags should be employed in

place of obsolete jute packaging to prevent post harvest losses during storage.

Retail display of potatoes in super markets should be carried out under

mercury and green lights for the prevention of alkaloidal toxicity and undesirable

greening.

Hot water treatment followed by Clove oil application should be used as an

alternate anti sprouting treatment in place of synthetic CIPC application to ensure

organic potato storage.

Pre processing application of Aloe vera gel at 20% proved to be efficient

technique to reduce fat absorption and toxic acrylamide formation along with

appreciable sensorial scores

Integrated post harvest management of potato variety “Lady Rosetta” on the

basis of best results identified ensured tuber dormancy and prolonged storage life up to

180 days in contrast to 100% observed sprouting in control on the 80th day of storage

311

312

LITERATURE CITED

Abbasi, K. S., M. Hassan and A. Ahmad. 2004. Effect of different ethylene absorbents

on the storage of banana (Musa cavendishii cv. Basrai). Pak. J. Arid. Agric.,

7(1): 1-11.

Abbasi, K. S., N. Anjum, S. Sammi, T. Masud and S. Ali. 2011. Effect of Coatings

and Packaging Material on the Keeping Quality of Mangoes (Mangifera indica

L.) stored at Low Temperature. Pak. J. Nutr., 10 (2): 129-138.

Abbasi, N.A., M. M. Kushad and A. G. Endress. 1998. Active Oxygen-scavenging

enzymes activities in developing apple flowers and fruits. Scientia Hort., 74:

183-194.

Aburjai, T. and F. M. Natsheh. 2003. Plants used in cosmetics. Phytother. Res., 17:

987-1000.

Afify, A. E.M. M.R., S. E.B. Hossam, A. A. Amina, E. E. A. Abeer. 2012. Antioxidant

enzyme activities and lipid peroxidation as biomarker for potato tuber stored

by two essential oils Caraway and Clove and its main component Carvone and

Eugenol. Asian Pac. J. Trop. Biomedicine, 1-9.

Aguilera, J. M. and H. Gloria-Hernandez.2000. Oil absorption during frying of frozen

par-fried potato. J. Food Sci., 65: 476-479.

Ahmadi, H., H. Fathollahzadeh and H. Mobli. 2008. Some physical and mechanical

properties of apricot fruits, pits and kernels (cv.Tabarzeh). American-Eurasian

J. Agric. Environ. Sci., 3(5): 703-707.

Albert, S. and G. S. Mittal. 2002. Comparative evaluation of edible coatings to reduce

312

313

fat uptake in a deep-fried cereal product. Food Res. Int., 35: 445–458.

Alsadon, A. A., A. M. Alhamdan and M. A. Obied. 2004. Effect of plastic packaging

on tomato fruits stored at different temperatures and high relative humidity: 1.

Quality attributes, Shelf life, and Chemical properties. Food Sci. Agric. Res.,

132: 5-28.

Amrein, T. M., B. Schonbachler, F. Escher and R. Amado. 2004. Acrylamide in

gingerbread: Critical factors for formation and possible ways for reduction. J.

Agric. and Food Chem., 52: 4282-4288.

Andersson, A., A. Gekas, I. Lind, F. Oliveira and R. O ste. 1994. Effect of

preheating on potato texture. Crit. Rev. Food Sci. Nutr., 34(3): 229–251.

Andre C. M., R. Schafleitner, C. Guignard, M. Oufir, C. A. A. Aliaga, G. Nomberto,

L. Hoffmann, J. F. Hausman, D. Evers, Y. Larondelle. 2009. Modification of

the health-promoting value of potato tubers field grown under drought stress:

emphasis on dietary antioxidant and glycoalkaloid contents in five native

Andean cultivars (Solanum tuberosum L.). J. Agric. Food Chem., 57: 599–609.

Andre, C. M., M. Ghislain, P. Bertin, M. Oufir, M. D. Herrera, L. Hoffmann, J. F.

Hausman, Y. Larondelle, and D. Evers. 2007. Andean potato cultivars

(Solanumtuberosum L.) as a source of antioxidant and mineral micronutrients.

J. Agric. Food Chem. 55: 366-378.

Anon. 1998. Potato industry digests, British Potato Council. Warwickshire, U.K.

Anthon, G. E. and D. M. Barrett. 2002. Kinetic parameters for the thermal inactivation

of quality-related enzymes in carrots and potatoes J. Agric. Food Chem., 50:

4119-4125.

314

Antolovich, M., P. D. Prenzler, E. Patsalides, S. McDonald and K. Robards. 2001.

Methods for testing antioxidant activity. Analyst, 127: 183–198.

AOAC. 1990. Official Methods of Analysis. Association of Analytical Chemists. 15th ed.,

Virginia, Arlington, USA.

AOAC. 1999. Official Methods of Analysis. Association of Official Analytical Chemists.

16th ed. Washington D.C, USA.

Arif, A., K. A. Tahsin, T. Muhammet and H. Baydar. 2010. Effects oF Caraway

(Carum carvi L.) seed on sprouting of potato (Solanum tuberosum L.) tubers

under different temperature conditions. Turk. J. Field Crops, 15(1): 54-58.

Arnao, M. B. 2000. Some methodological problems in the determination of

antioxidant activity using chromogen radicals: A practical case. Tr. Food Sci.

Technol., 11: 419-421.

Arnao, M. B., A. Cano and M. Acosta. 1999. Methods to measure the antioxidant

activity in plant material. A comparative discussion. Free Radic. Res., 31: 589-

596.

Arts, I.C. and P.C. Hollman. 2005. Polyphenols and disease risk in epidemiologic

studies. Am. J. Clin. Nutr., 81: 3 17-325.

Aydin, N. and A. Kadioglu. 2001. Changes in the chemical composition, polyphenol

oxidase and peroxidase activities during development and ripening of Medlar

fruits (Mespilus germanica L.). Bulg. J. Plant Physiol., 27(3–4): 85–92.

Babarinde, G. O. and O. A. Fabunmie. 2009. Effects of packaging material and storage

temperature on the quality of fresh okra (Abelmoschus esculentus) fruit.

Agricultura Tropica et sub Tropica, 42 (4): 151-156.

315

Bachmann, J. and R. Earles. 2000. Postharvest handling of fruits and vegetables.

Appropriate Technology Transfer for Rural Areas. pp.1-19.

<http://www.ozoneindustries.com.au/images/tech postharvest.pdf> (accessed

on 28/08/2010).

Bachmann, J. and R. Earles. 2000. Post harvest handling of fruits and vegetables.

ATTRA Horticultural Technical Note. P.O.Box 3838 Butte, MT 59701

USA pp:19.

Badshah, N., S. Mohammad, M. Qaim and S. Ayaz. 1997. Shelf life study on tomato

storage with different packing materials. Sarhad J. Agric., 13: 347-356.

Bajji, M., M. Hamdi, F. Gastiny, A. Jorge, J. A. R. Beltran and P. DuJardin. 2007.

Catalase inhibition accelerates dormancy release and sprouting in potato

(Solanum tuberosum L.) tubers. Biotechnol. Agron. Soc. Environ., 11(2):121-

131.

Baldwin, S.J., K.G. Dodds, B. Auvray, R.A. Genet, R.C. Macknight and J.M.E

Jacobs. 2011. Association mapping of cold-induced sweetening in potato

using historical phenotypic data. Annals Applied Biol., 158 (3): 248–256.

Bamnolker, T. P., N. Dudai, R. Fischer, E. Belausov, H. Zemach, O. Shoseyov, D.

Eshel . 2010. Mint essential oil can induce or inhibit potato sprouting by

differential alteration of apical meristem. Planta, 232 (1):179-186.

Banaras, M., P. W. Bosland and N. K. Llownds. 2005. Effects of harvest time and

growth conditions on storage and post-storage quality of fresh peppers

(capsicum annuum l.). Pak. J. Bot., 37(2): 337-344.

Barberan, F. A. T. and J. C. Espín. 2001. Phenolic compounds and related enzymes as

316

determinants of quality in fruits and vegetables. J. Sci. Food Agric., 8 (I9):

853–876.

Barth, M. M. and H. Zhang. 1996. Packaging design effects antioxidant vitamin

retention and quality of broccoli florets during postharvest storage. Postharvest

Biol. Technol., 9: 141-150.

Baryeh, E. A. 2001. Physical properties of Bambara groundnuts. J. Food Engin., 47:

321-326

Baskaran, R., A. U. Devi, C. A. Nayak, V. B. Kudachikar, M. N. K. Prakash, M.

Prakashc, K. V. R. Ramana and N. K. Rastogi. 2007. Effect of low-dose g-

irradiation on the shelf life and quality characteristics of minimally processed

potato cubes under modified atmosphere packaging. Rad. Phy. Chem.,

76:1042–1049.

Basuny, A. M. M., D. M. M. Mostafa and A. M. Shaker. 2009. Relationship between

chemical composition and sensory evaluation of chip made from six potato

varieties with emphasis on the quality of fried sunflower oil. World J. Dairy

Food Sci., 4 (2): 193-200.

Batu, A. and A. K. Thompson. 1998. Effects of Modified Atmosphere Packaging on

Post Harvest Qualities of Pink Tomatoes. Tr. J. Agric. Forestry, 22: 365-372.

Beaudry, R. M. 1999. Effect of O2 and CO2 partial pressure on selected phenomena

affecting fruit and vegetable quality. Postharvest Biol. Technol., 15:293-303.

Bejarano, L., E. Mignolet, E. Devaux, E. Carrasco and Y. Larondelle. 2000.

Glycoalkaloids in potato tubers: the effect of variety and drought stress on

the a-solanine and a-chaconine contents of potatoes. J. Sci. Agric. 80:

317

2096–2100.

Beltran, D., M. V. Selma, J. A. Tudela and M. I. Gil. 2005. Effect of different

sanitizers on microbial and sensory quality of fresh-cut potato strips stored

under modifiedatmosphere or vacuum packaging. Postharvest Biol. Technol.

37:37–46.

Berry, S. K., R. C. Sehgal and C. L. Kalra. 1999. Comparative oil uptake by potato

chips during frying under different conditions. J. Food Sci. Technol., 36: 519–

521.

Beukema H.P., Van der Zaag D.E. 1990. Introduction to potato production. PUDOC.

Wageningen, pp.111-123.

Beukema, H. P. and D. E. V. Zaag. 1990. Introduction to potato production. Pudoc,

Wageningen, The Netherlands.

Biedermann-Brem S., A. Noti, K.Grob, D. Imhof, D. Bazzocco and A. Pfefferle. 2003.

How much reducing sugar may potatoes contain to avoid excessive acrylamide

formation during roasting and baking? Eur. Food Res. Technol., 217: 369-373.

Biemelt, S., M. Hajirezaei, E. Hentschen and U. Sonnewald. 2000. Comparative

analysis of abscisic content and starch degradation during storage of tubers

harvested of different potato varieties. Potato Res., 43: 371–382.

Blenkinsop, R. W., L. J. Copp, R.Y. Yada and A.G. Marangoni. 2002. Changes in

compositional parameters of potato (Solanum tuberosum) during low-

temperature storage and their relationship to chip processing quality. J. Agric.

Food Chem., 50: 4545-4553.

318

Blessington, A., J. C. Miller, M. N. Nzaramba, A. L. Hale, L. Redivari, D. C.

Scheuring, G. J. Hallman. 2007. The effects of low-dose gamma irradiation

and storage time on carotenoids, antioxidant activity, and phenolics in the

potato cultivar Atlantic. Am. J. Potato Res., 84 (2): 125-131.

Bouchan, P and D. L. Pyle. 2004. Studying oil absorption in restructured potato chips.

J.Food Sci., 69 (3): 115-122.

Bouwmeester, H.J., J. Gershenzon, M. Konings and R. Croteau. 1998. Biosynthesis of

the monoterpenes limonene and carvone in the fruit of caraway - I.

Demonstration of enzyme activities and their changes with development. Plant

Physiol., 117: 901-12.

Bravo, L. 1998. Polyphenols: Chemistry, dietary sources, metabolism, and nutritional

significance. Nutr. Rev., 56: 317-333.

Bryant, P. 2004. Optimising the Postharvest Management of Lychee (Litchi

chinensis Sonn.) A Study of Mechanical Injury and Desiccation. Ph.D Thesis.

University of Sydney, Sydney, 24 pp.

Buchanan, B. B., W. Gruissem and R. L. Jones. 2000. Biochemistry and Molecular

Biology of Plants: American Society of Plant Physiologists, Rockville, USA.

pp.1251–1292.

Burlingame, B., B. Mouille and R. Charrondiere. 2009. Nutrients, bioactive non-

nutrients and anti-nutrients in potatoes- A Critical Review. J. Food

Composition Anal., 22: 494–502.

Burton, W. G., A. Vanes and K. J. Hartmans. 1992. The physics and physiology of

storage: The potato crop. In P. M. Harris (Ed.), Chapman and Hall, London.

319

Calderon, M. M., M.A.R. Grau, O. M. Belloso. 2008. Effect of packaging conditions

on quality and shelf life of fresh cut pineapple (Ananas comosus). Post harvest

Biol. Technol., 50(2-3): 182-189.

Caldiz, D. O., L. V. Fernandez and M. H. Inchausti. 2001. Maleic hydrazide effects on

tuber yield, sprouting characteristics and French fry processing quality in

various potato (Solanum tuberosum L.) cultivars grown under Argentinian

conditions. Am. J. Potato Res., 78: 119-128.

Camire, M. E., R. J. Bushway, J. Zhao, B. Perkins and L. R. Paradis. 1995. Fate of

thiabendazole and chlorpropham residues in extruded potato peel. J. Agri.

Food Chem., 43(2):495-497.

Cantos, E., J. A. Tudela, M. I. Gil and J. C. Espin. 2002. Phenolic compounds and

related enzymes are not rate-limiting in browning development of fresh cut

potatoes. J. Agric. Food Chem., 50: 3015-3023.

Casanas, R., M. Gonzalez, E. Rodriquez, A. Marrero and C. Diaz. 2002. Chemometric

studies of chemical compounds in five cultivars of potatoes from Tenerife. J.

Agri. Food Chem., 50: 2076–2082.

Casanas, R., P. L. Suarez, E. M. Rodriquez, A. Marrero and C. Diaz. 2009. Chemical

composition of eight cultivars of potatoes. Application of multivariant

analysis. Acta Alimentaria, 38(4): 405-414.

Chang, C. Y., Y. R. Tsai and W. H. Chang. 1993. Models for the interactions between

pectin molecules and other cell-wall constituents in vegetable tissues. Food

Chem., 48: 145-150.

Chauhan S. S., O. Prakash, R. C. Padalia, A. K. Vivekanand, C. Pant and S. Mathela.

320

2011. Chemical diversity in Mentha spicata: antioxidant and potato sprout

inhibition activity of its essential oils. Nat. Prod. Commun., 6 (9):1373-1378.

Chen, C.T. and T. L. Setter. 2003. Response of potato tuber cell division and growth to

shade and elevated CO2. Annals Botany, 91: 373-381.

Chen, F. H., G. B. Wu and C. F. Li. 2003. Effects of modified atmosphere packaging

on respiration and quality attributes of loquat fruit during cold storage. Trans.

Chi. Soc. Agric. Engrr., 19(5): 147-151.

Cho Y. K. and H. K. Ahn. 1999. Purification and characterization of polyphenol

oxidase from potato: II. Inhibition and catalytic mechanism. J. Food Biochem.,

23: 577–592.

Choi, E. and S. Koops. 2005. Anti-nociceptive and anti-inflammatory effects of the

ethanolic extract of potato (Solanum tuberosum). Food Agric. Immunol., 16:

29–39.

Choi, J. H. and S. Koo. 1997. Effect of MA storage on wooliness of ‘Yumyeong’

peaches. Postharvest Hortic. Ser., 3: 132–138.

Christie, P. J., M. R. Alfenito and V. Walbot. 1994. Impact of low temperature stress

on general phenylpropanoid and anthocyanin pathways: enhancement of

transcript abundance and anthocyanin pigmentation in maize seedlings. Planta,

194: 541-549.

Christine, I. 1996. The Vegetable Ingredients Cookbook by, Lorenz Books, 1996

ISBN 1-85967-264-7

Chu, Y. H., C. L. Chang and H. F. Hsu. 2000. Flavonoid content of several vegetables

and their antioxidant activity. J. Sci. Food Agric., 80: 561-566.

321

Chuda, Y., H. Ono, H. Yada, T. A.Ohara, C. M. Endo and M. Mori. 2003. Effects of

physiological changes in potato tubers (Solanum tuberosum L.) after low

temperature storage on the level of acrylamide formed in potato chips. Biosci.

Biotechnol. Biochem., 67: 1188-1190.

CIP (International Potato Center), Annual Report, 1997. pp: 239-264.

Claassens M.M.J., D. Vreugdenhil. 2000. Is dormancy breaking of potato tubers the

reverse of tuber initiation? Potato Res., 43: 347-69.

Clark, J. P. 2003. Happy birthday, potato chips and other snack developments. J. Food

Technol., 57(5): 89-92.

Conte A., C. Socrocco, L. Lecce, M. Mastromatteo, M.A.D. Nobile. 2009. Ready-to-

eat sweet cherries: Study on different packaging systems. Innovative Food Sci.

Emer. Technol.,10(4): 564-571.

Crumiere, F. 2000. Inhibition of enzymatic browning in food products using Bio-

Ingredients. M.Sc. Diss. Deptt. of Food Science and Agric. Chemistry. McGill

University. Montreal, Québec.

Cunningham, H. H., M. V. Zaehringer and W. C. Sparks. 1971. Effect of storage

temperature and sprout inhibitors on mealiness, sloughing and specific gravity

of Russet Burbank potatoes. Am. J. Potato Res., 43(1): 10-21.

Dale, M. B. F., D. W. Griffiths, H. Bain and D. Todd. 1993. Glycoalkaloid increase in

Solanum tuberosum on exposure to light. Ann. Appl. Biol. 123: 411-418.

Dale, M. F. B., D. W. Griffiths and D. T. Todd. 2003. Effects of genotype,

environment, and postharvest storage on the total ascorbate content of potato

(Solanum tuberosum) tubers. J. Agri. Food Chem., 51: 244-248.

322

Das, E., G. C. Gurakan and A. Bayinirli. 2006. Effect of controlled atmosphere

storage, modified atmosphere packaging and gaseous ozone treatment on the

survival of Salmonella Enteritidis on cherry tomatoes. Food Microbiol., 23:

430-438.

Davey, M. W., M. V. Montagu, D. Inze, M. Sanmartin, A. Kanellis, N. Smirnoff, I. F.

Benzie, J. J. Strain, D. Favell and J. Fletcher. 2000. Plant L-ascorbic acid:

chemistry, function, metabolism, bioavailability and effects of processing. J.

Sci. Food Agric., 89: 825–860.

Davies C. S., M. J. Ottman and S. J. Peloquin. 2002 .Can germplasm resources be used

to increase the ascorbic acid content of stored potatoes? Am. J. Potato Res., 79:

295–299.

DeWilde, T., B. DeMeulenaer, F. Mestdagh, R. Verhé, Y. Govaert, S. Fraselle, J.M.

Degroodt, S. Vandeburie, K. Demeulemeester, A. Calus, W. Ooghe and C. V.

Peteghem. 2004. Acrylamide formation during frying of potatoes: Thorough

investigation on the influence of crop and process variables. Czech. J. Food

Sci., 22:15-18.

Delaplace P., J. R. Beltran, P. Frettinger, P. D. Jardin and M. Fauconnier. 2008.

Oxylipin profile and antioxidant status of potato tubers during extended

storage at room temperature. Plant Physiol. Biochem., 46: 1077-1084.

Dewilde, T., B. Demeulenaer and F. Mestdagh. 2006. Selection criteria for potato

tubers to minimize acrylamide formation during frying. J. Agric. Food Chem.,

54: 2199–2205.

Ding. Z., S. Tian, Y. Wang, B. Li, Z. Chan, J. Hana and Y. Xua. 2006. Physiological

323

response of loquat fruit to different storage conditions and its storability.

Postharvest Biol. Technol., 41: 143-150.

Ding, C. K., Y. Chachin, Y. Ueda, Y. Imahori and C.Y. Wang. 2002. Modified

atmosphere packaging maintains postharvest quality of loquat fruit.

Postharvest Biol. Technol., 24(3): 341-348.

Ding, C. K., Y. U. Chachin, Y. Ueda, Y. Imahori and H. Kurooka. 1999. Effects of

high CO2 concentration on browning injury and phenolic metabolism in loquat

fruits. J. Jap. Soc. Hort. Sci., 68: 275–282.

Ding, C. K., K. Chachin, Y. Ueda and Y. Imahori. 1998. Purification and properties of

polyphenol oxidase from loquat fruit. J. Agric. Food Chem., 46: 4144-4149.

Diplock, A.T., J. L. Charleux, G. C. Willi, F. J. Kok, C. R. Evans, M. Roberfroid, W.

Stahl and J. Vina-Ribes. 1998. Functional food science and defence against

reactive oxidative species. Br. J. Nutr. 80 (1): 77-112.

Dorland’s Illustrated Medical Dictionary .1994. W.B Saunders, Philadelphia (28th

edn).

Durand, K. M. D. 2006. Modified atmosphere packages and post-harvest quality of

pigeon pea. M.Sc. Diss. University of Porto Rico.

Edwards E. J. and A.H. Cobb. 1996. Improved high-performance liquid

chromatographic method for the analysis of potato (Solanum tuberosum)

glycoalkaloids. J. Agric. Food Chem., 44:2705–2709

Edwards E. J. and A.H. Cobb. 1997. Effect of temperature on glycoalkaloid and

chlorophyll accumulation in potatoes (Solanum tuberosum L. cv King Edward)

stored at low photon flux density, including preliminary modeling using an

324

artificial neural network. J. Agric. Food Chem., 45: 1032–1038.

Edwards, C. G., J. W. Engler, C. R. Brown, J. C. Peterson and E. J. Sorensen. 2002.

Changes in colour and sugar content of yellow-fleshed potatoes stored at three

different temperatures. Am. J. Potato Res., 79: 49-53.

Edwards, E. J. and A. H. Cobb. 1996. Improved high-performance liquid

chromatographic method for the analysis of potato (Solanum tuberosum)

glycoalkaloids. J. Agric. Food Chem., 44: 2705–2709

Eldredge, E. P., Z. A. Halmas, A.R. Mosley, C. C. Shock and T. D. Stieber. 1996.

Effect of transitory water stress on potato tuber stem end reducing sugar and

fry colour. Am. Potato J. 73: 517-529.

El-hilali, F., A. Ait-Oubahou, A. Remah and O. Akhayat. 2003. Chilling injury and

peroxidase activity changes in “fortune” mandarin fruit during low temperature

storage. Bulg. J. Plant Physiol., 29(1–2): 44–54.

Endo, C. M., A. O. Takada, Y. Chuda, H. Ono, H. Yada, M. Yoshida, A. Kobayashi,

S. Tsuda, S.Takigawa, T. Noda, H. Yamauchi and M. Mori. 2006. Effects of

storage temperature on the contents of sugars and free amino acids in tubers

from different potato cultivars and acrylamide in chips. Biosci. Biotechnol.

Biochem., 70 (5): 1173-1180.

Eshun, K. and Q. He. 2004. Aloe vera: a valuable ingredient for the food,

pharmaceutical and cosmetic industries a review. Crit. Rev. Food Sci. Nutr.,

44: 91-96.

Exama, A., J. Arul, R.W. Lencki, L. Z. Leee and C. Toupin. 1993. Suitable of plastic

325

films for modified atmosphere packaging of fruits and vegetables. J. Food Sci.,

58:1365-1370.

FAO. 2007. Food Outlook No. 1, FAO, Rome.

Farooqi, A. H. A., K. K. Agarwal, F. Shabih, A. Ahmad, S. Sharma and S. Kumar.

2001. Acyclic monoterpenes as anti-sprouting agents for potato tubers. European

Patent Application PCT/IN00/00034.

Farre E. M., A. Bachmann, L. Willmitzer, R. N. Trethewey. 2001. Acceleration of

potato tuber sprouting by the expression of a bacterial pyrophosphatase. Nature

Biotechnol., 19, 268-272.

Fennema, O. 1996. Food Chemistry. (3rd ed.). New York: Marcel Dekker.

Fennir, M. A. 2002. Respiratory response of healthy and diseased potatoes (Solanum

tuberosum L.) under real and experimental storage conditions. Ph.D Thesis,

Deptt of Agric. and Biosystem Engineering, McGill Univ. Montreal.

Fernández, P. M. S., D. Villano, P.M.C. García and A. M. Troncoso. 2004.

Antioxidant activity of wines and relation with their polyphenolic composition.

Anal. Chem. Acta, 513: 113-118.

Fernie, A. R., L. Willmitzer and R. N. Trethewey. 2002. A review: Sucrose to

starch: a transition in molecular plant physiology. Trends Plant Sci.,

7(1):35-41

Fiselier, K., K. Grob and A. Pfefferle. 2004. Brown potato croquettes low in

acrylamide by coating with egg/breadcrumbs. Eur. Food Res. Technol.,

219(2):111-115.

Fonseca, S. C., F.A.R. Oliveira and J. K. Brecht. 2002. Modeling respiration rate of

326

fresh fruits and vegetables for modified atmosphere packages: A review. J.

Food Engin., 52: 99–119

Francois, A. T. and J. C. Espin. 2001. Phenolic compounds and related enzymes as

determinants of quality in fruits and vegetables. J. Sci. Food Agric., 81(9):853-

976.

Frazier, M. J., N. L. Olsen and G. E. Kleinkopf. 2004. Organic and alternative

methods of potato sprout control in storage. University of Idaho

Extension, Accessed at: http://info.ag.uidaho.edu/pdf/CIS/CIS 11 20.pdf

Friedman, M. 1997. Chemistry, biochemistry, and dietary role of potato polyphenols.

A review. J. Agric. Food Chem., 45: 1523-1540.

Friedman, M. 2004. Analysis of biologically active compounds in potatoes (Solanum

tuberosum), tomatoes (Lycopersicon esculentum), and jimson weed

(Datura stramonium) seeds. J. Chromatogr., 1054: 143-155.

Friedman, M. 2006. Potato glycoalkaloids and metabolites: roles in the plant and in the

diet. J. Agric. Food Chem., 54: 8655–8681.

Friedman, M., J. N. Roitman and N. Kozukue. 2003. Glycoalkaloid and calystegine

contents of eight potato cultivars. J. Agric. Food Chem. 51: 2964–2973.

Gachango, E., S. I. Shibairo, J. N. Kabira, G. N. Chemining and P. Demo. 2008.

Effects of light intensity on quality of potato seed tubers. Afric. J. Agric. Res.,

3(10): 732-739.

Gamble, M. H and P. Rice. 1988. The effect of slice thickness on potato crisp yield

and composition. University of Technology, Loughborough, Leicestershire

LE11 3TU, UK.

327

García, M. A., C. Ferrero, N. Bértola, M. Martino and N. Zaritzky. 2002. Edible

coatings from cellulose derivatives to reduce oil uptake in fried products.

Innov. Food Sci. Emer. Technol., 3: 391–397.

Garmakhany, A. D., H. Mirzaei, M. K. Nejad and Y. Maghsudlo. 2008. Study of oil

uptake and some quality attributes of potato chips affected by hydrocolloids.

Eur. J. Lipid Sci. Technol., 110: 1045–1049.

Gaur, P. C., S. V. Singh, S. K. Pandey, R. S. Marwaha, D. Kumar and D. Kumar.

1999. Kufri Chipsona2: A new high dry matter potato variety for chipping.

Current Sci.,76: 722- 724.

Gennadios, A., M.A. Hanna and L. B. Kurth. 1997. Application of edible coatings on

meats, poultry and seafoods: a review. Food Sci. and Technol.–Lebensmittel-

Wissenschaft & Technologie, 30: 337–350.

Ghazavi, M. A., and S. Houshmand. 2010. Effects of Mechanical Damage and

Temperature on Potato Respiration Rate and Weight Loss. World Appl. Sci. J.,

8(5): 647- 652.

Goggs, R., A. V. Thomas, P. D. Clegg, S. D. Carter, J. F. Innes and A. Mobasheri, A.

2005. Nutraceutical therapies for degenerative joint diseases: A critical review.

Crit. Rev. Food Sci. Nutr., 45: 145- 164.

Gomez, R., J. E. Pardo, M. Amo, R. Varon and F. Navarro. 1997. Evaluacin de la

calidad de cultivares de patata de siembra. II. Determinacion y cuantificacion

de parhetros quimicos. Actas de Horticultura, 20: 1069- 1074.

Gonzalez, A., C. S. R. Cruza, R. C. Valenzuelaa, A. R. Flelixa and C. Y. Wang. 2004.

Physiological and quality changes of fresh-cut pineapple treated with

328

antibrowning agents. Lebensm.Wiss. Technol., 37: 369–376.

Gorris, L. G. M., K. Oosterhaven, K. J. Hartmans, Y. D. Witte and E. J. Smid. 1994.

Control of fungal storage diseases of potato by use of plant-essential oil

components. Brighton Crop Protection Conference - Pests and Diseases,

1994. Volume 1, pp. 307-312.

Gosselin, B. and N. I. Mondy. 1989. Effect of packaging materials on the chemical

composition of potatoes. J. Food Sci., 54: 629–631.

Gould, W. 1995. Specific gravity its measurement and use. Chipping Potato

Handbook, pp. 18-21.

Gould, W.A. 1999. Potato production, processing, and technology. CTI Publications,

Baltimore, M.D

Government of Pakistan (GOP). 2009. Economic Survey, Finance Division, Economic

Advisors Wings, Islamabad- Pakistan.

Granda, C., R. G. Moreira and S. E. Tichy. 2004. Reduction of acrylamide formation

in potato chips by low-temperature vacuum frying. J. Food Sci., 69: E405-

E411.

Gravoueille, J. M. 1999. Utilization en la alimentacion humana (Use in the human

feeding) Rouselle P., Y. Robert and J. C. Crosnier. (Eds). La Patato (The

potato) Mundi prensa, Madrid, pp: 459-508.

Griffiths, D. W., M. F. B. Dale and H. Bain. 1994. The effect of cultivar,

maturity and storage on photo-induced changes in the total glycoalkaloid

and chlorophyll contents of potatoes (Solanum tuberosum). Plant Sci.,

98:103–109.

329

Griffiths, D. W., H. Bain, M. F. B. Dale. 1995. Photo-induced changes in the total

chlorogenic acid content of potato (Solanum tuberosum) tubers. J. Sci. Food

Agric., 68: 105-110.

Grunenfelder L. A., L. O. Knowles, L. K. Hiller and N. R. Knowles. 2006.

Glycoalkaloid development during greening of fresh market potatoes (Solanum

tuberosum L.). J. Agri. Food Chem., 54(16): 5847–5854.

Haase, N. U., B. Mattahaus and K. Vosmann. 2003. Minimierungsansatze zur

Acrylamid-Bildung in pflanzlichen Lebensmitteln-aufgezeigt am Beispiel

vonKartoffelchips. Deutsche Lebensmittel-Rundschau, 99: 87-90.

Haase, N. U. 2008. Healthy aspects of potatoes as part of the human diet. Potato Res.,

51: 240-258

Hagenimana, V., E. G. Karuri, and M. A. Oyunga. 1998. Oil content in fried

processed sweet potato products. J. Food Process. Preserv. 22:123-137.

Haila, K. 1999. Effects of Carotenoids and Carotenoid-Tocopherol Interaction on

Lipid Oxidation In-Vitro. 1) Scavenging of Free Radicals. 2) Formation and

Decomposition of Hydroperoxides. Diss. Department of Applied Chemistry

and Microbiology. University of Helsinki, EKT-series 1165.

Hajirezaei, M. R., F. Bornke, M. Peisker, Y. Takahata, J. Lerchl, A. Kirakosyan and

U. Sonnewald. 2003. Decreased sucrose content triggers starch breakdown and

respiration in stored potato tubers (Solanum tuberosum). J. Exp. Bot., 54 (382):

477-488.

Hamauzu, Y. 2006. Role and evolution of fruit phenolic compounds during ripening

and storage. Stewart Postharvest Review, p. 2-5.

330

Hamouz, K., J. Lachman, P. Dvorak, M. Juzl and V. Pivec. 2006. The effect of site

conditions, variety and fertilization on the content of polyphenols in potato

tubers. Plant, Soil Environ., 52: 407–412.

Harborne, J. B. 1998. The flavonoids, advances in research since 1986. Chapman and

Hall, London.

Hartmans, K. J., P. Diepenhorst, W. Bakker and L. G. M. Gorris. 1995. The use of

carvone in agriculture - sprout suppression of potatoes and antifungal activity

against potato-tuber and other plant-diseases. Industrial Crops Products, 4:

3-13

Hawkes, J. G. 1978a. History of the potato. In: P. M. Harris (Ed.). The potato crop.

Halsted, New York p. 1-13.

Hay, R. K. M. 1993. Volatile oil crops: their biology, biochemistry and

production. Longman Scientific and Technical, Harlow UK.

Haynes, K. G. 2001. Variance components for yield and specific gravity in a diploid

potato population after two cycles of recurrent selection. Am. J. Potato Res.,

78: 69-75.

Hejtmankova, K., V. Pivec, E. Trnkova, K. Hamouz and J. Lachman. 2009. Quality of

coloured varieties of potatoes. Czech. J. Food Sci., 27: 310-313.

Herman, T. J., S. L. Love, B. Shafii and R. B. Dwelle. 1996. Chipping performance of

three potato cultivars during long term storage at two temperature regimes.

Am. Potato J., 73: 411-425.

Hertog, M. L. A. T. M., L. M. M. Tijskens and P. S. Hak. 1997. The effects of

temperature and senescence on the accumulation of reducing sugars during

331

storage of potato (Solanum tuberosum L.) tubers: a mathematical model.


Hironaka, K., K. Ishibashi and K. Hakamada. 2001. Effect of static loading on sugar

contents and activities of invertase, UDP glucose pyrophosphorylase and

sucrose 6-phosphate synthase in potatoes during storage. Potato Res., 44:33-

39.

Hong, S. L. and J. M. Krochta. 2003. Oxygen Barrier Properties of Whey Protein

Isolate Coating on Polypropylene Films. J. Food Sci., 68: 224–228.

Huang, D. J., B.X. Ou and R. L. Prior. 2005. The chemistry behind antioxidant

capacity assays. J. Agric. Food Chem., 53: 1841-1856.

Hubbard, L. J. and B. E. Farkas, 1999. A method for determining the convective

heat transfer coefficient during immersion frying. J. Food Proc. Engin., 22:

201–214.

Huse, H. L., P. Mallikarjunan, M. S. Chinnan, Y. C. Hung and R. D. Phillips. 1998.

Edible coatings for reducing oil uptake in production of akara (deep-fat frying

of cowpea paste). J. Food Proc. Pres., 22: 155 –165.

Hussain, S. P., L. J. Hofseth and C. C. Harris. 2003. Radical causes of cancer. Nat.

Rev. Cancer. 3: 276-285.

IARC (International Agency for Research on Cancer). 1994. Acrylamide. IARC

Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to

Humans, 60, IARC, Lyon, France, pp. 389-433.

Ibrahim, F. E., 2005. Effect of post harvest treatments on storage ability and keeping

quality of Amaar apricot fruits. Ann. Agri. Sci. Moshtohors, 43: 849-867.

332

IQS. 2005. Industrial Quick Search, Inc. www.plastic-bags.net/info/index.htm.

Searched on 12-03-2010).

Isman M. B. 2006. Botanical insecticides, deterrents, and repellents in modern

agriculture and an increasingly regulated world. Ann. Rev. Entomol., 51: 45-

66.

Jaswal, A. S. 1991. Texture of french fried potato: quantitative determinations of non-

starch polysaccharides. Am. Potato J., 68: 171–177.

Jaswir, I., Y. B. C. Man and D. D. Kitts. 2000. Use of natural antioxidants in refined

palmolein during repeated deep fat frying. J. Food Res. Intl., 33: 501-508.

Javanmardi, J. and C. Kubota. 2006. Variation of lycopene, antioxidant activity, total

soluble solids and weight loss of tomato during postharvest storage.


JECFA (Joint FAO/WHO Expert Committee on Food Additives). 1993. Solanine

and chaconine. In: Toxicological Evaluation of Certain Food Additives and

Naturally Occurring Toxicants, prepared by the 39th Meeting of the

JECFA, WHO Food Additives series: 30. W. H. O. Geneva.

Jiang, Y and Y. Li. 2001. Effects of chitosan coating on post harvest life and quality of

longan fruit. Food Chem., 73(2): 139-143.

Jimenez, M., E. Trejo, M. Cantwell and J. Santellano. 1996. Cherry tomato storage

and quality evualuation. Tulare country vegetable research report online. The

university of California cooperative extension, Tulare country.

(http://cetulare.ucdavis.edu./pubveg/che96.htm) Accessed on 28th June, 2010.

Joyce, D. and B. Patterson. 1994. Postharvest water relations in horticultural crops:

333

principles and problems. ACIAR Proceedings, 50: 228-238.

Jung, M.Y., D.S. Choi,. and J.W. Ju. 2003. A novel technique for limitation of

acrylamide formation in fried and baked corn chips and in French fries. J.Food

Sci., 68: 1287-1290.

Junior, F. M., R. Deliza and A.B. Chitarra. 2002. Alteracoes sensoriais em alface

hidroponica cv. Regina minimamente processada e armazenada sob

refrigeracao. Hortic.Bras., 20: 63-66.

Junker, B. H., R. Wuttke, A. N. Nesi, D. Steinhauser, N. Schauer, D. Bussis, L.

Willmitzer and A. R. Fernie. 2006. Enhancing vacuolar sucrose cleavage

within the developing potato tuber has only minor effects on metabolism. Plant

Cell Physiol., 47: 277–289.

Kabira, J.N. and B. Lemaga. 2003. Potato processing quality evaluation procedures for

research and food industry applications in East and Central Africa. Green

printers stationers. p.24.

Kader, A. A. 2002. Recommendations for maintaining postharvest quality. Post

harvest Technology Research Information Center. Deptt. of Pomology. Univ. of

California. One Shield Ave., Davis, CA., 95616-8683.(n.p)

Kalt, W. 2005. Effects of production and processing factors on major fruit and

vegetable antioxidants. J. Food Sci., 70: R11–R19.

Kant, A.K. and G. Block. 1990. Dietary vitamin-B6 intake and food sources in the

United-States population - Nhanes Ii, 1976-1980. Am. J. Clin. Nutr. 52: 707-

716.

Karim, M. R., M. M. H. Khan, M. Salim Uddin, N. K. Sana, F. Nikkon and M. Habib-

334

ur-Rahman. 2008. Studies on the sugar accumulation and carbohydrate

splitting enzyme levels in post harvested and cold stored potatoes. J. Bio-Sci.

16: 95-99.

Kaul, A.D., P. Kumar, V. Hooda and A. Sonkusare. 2010. Biochemical behaviour of

different cultivars of potato tuber at different storage conditions. National

Conference on Computational Instrumentation CSIO Chandigarh, INDIA. pp.

172-176.

Kaur, C. and H. C. Kapoor. 2002. Anti-oxidant activity and total phenolic content of

some Asian vegetables. Int. J. Food Sci. Technol. 37:153–161.

Kaur, C. and H. C. Kapoor. 2001. Antioxidants in fruits and vegetables-the

millennium’s health. Intl. J. Food Sci. Tech., 36: 703–25.

Kays, J. S. 1991. Post-harvest physiology of perishable plant products, Van Nostrand

and Reinhold Book Publishing Co., New York, pp.532.

Kazami, D., T. Tsuchiya, Y. Kobayashi and N. Ogura. 2000. Effect of storage

temperature on quality of potato tubers. J. Jap. Society Food Sci. Technol.,

47(11): 851–856.

Kerstholt, R. P. V., C. M. Ree and H. C. Moll. 1997. Environmental life cycle analysis

of potato sprout inhibitors. Industrial Crops Products, 6:187-194.

Khuyen, T. H., Z. Singh and E. Ewald. 2008. Edible Coatings Influence Fruit

Ripening, Quality and Aroma Biosynthesis in Mango Fruit. J. Agric. Food

Chem., 56:1361–1370.

Kim D. M., N. L. Smith and C. Y. Lee. 1993. Apple cultivar variations in response to

heat treatment and minimal processing. J. Food Sci., 58: 1111–1114.

335

Kita, A. 2002. The influence of potato chemical composition on crisp texture. Food

Chem., 76: 173-179.

Kita, A., E. Brathen, S. Knutsen and T. Wicklund. 2004. Effective ways of decreasing

acrylamide content in potato crisps during processing. J. Agric. Food Chem.,

52: 7011-7016.

Kita, A., G. Lisinska and M. Powolny. 2005. The influence of frying media degree of

degradation on fat uptake and texture of French fries. J. Sci. Food Agric.,

85:113–118.

Kita, A., G. Lisinska, A. T. Czopek and E. Rytel. 1998. The effects of potato

variety and other factors on fat contents of chips. In International

conference: The present and future of crop science and bee keeping (pp.

231–238). Kaunas: Lithuanian Agricultural Academy.

Kittur, F. S., N. Saroja, Haibibunnisa and R. N. Tharannathan. 2001. Polysaccharide-

based composite coating formulations for shelf life extension of fresh banan

and mango. Eur. Food Res. Technol., 213: 306-311.

Kittur, F. S., K. R. Kumar and R. N. Tharanathan. 1998. Functional Packaging

Properties of Chitosan Films. Eur. Food Res. Technol., 44: 206–208.

Kleinkopf, G. E., N. A. Oberg and N. L. Olsen. 2003. Sprout inhibition in storage:

current status, new chemistries and natural compounds. Am. J. Potato Res.,

80: 317-27.

Knowles, N. R., E. D. Driskill and L. O. Knowles. 2009. Sweetening response of

potato tubers of different maturity to conventional and non-conventional

storage temperature regimes. Postharvest Biol. Technol., 52: 49-61.

336

Koeduka, T., E. Fridman, D. R. Gang, D. G. Vassao, B. L. Jackson, C. M. Kish, I.

Orlova, S. M. Spassova, N. G. Lewis, J. P. Noel, T. J. Baiga, N. Dudareva and

E. Pichersky. 2006. Eugenol and isoeugenol, characteristic aromatic

constituents of spices, are biosynthesized via reduction of a coniferyl alcohol

ester. Proceedings of the National Academy of Sciences of the USA,

103(10):128-133.

Kojo, S. 2004. Vitamin C: Basic metabolism and its function as an index of

oxidative stress. Curr. Med. Chem., 11: 1041-1064.

Kolasa, K.M. 1993. The potato and human nutrition. Am. Potato J., 70: 375-384.

Kolbe, H., K. Muller, G. Olteanu and T. Gorea. 1995. Effects of nitrogen, phosphorus

and potassium fertilizer treatments on weight loss and changes in chemical

composition of potato tubers stored at 4C. Potato Res., 38: 97-107.

Koleva, I. I., T. A. Van Beek, J. P. H. Linssen, A. D. Groot and L. N. Evstatieva. 2002.

Screening of plant extracts for antioxidant activity: A comparative study on

three testing methods. Phytochem. Anal., 13: 8-17.

Komiyama, S., J. Kato, H. Honda and K. Matsushima. 2007. Development of sorting

system based on potato starch content using visible and near-infrared

spectroscopy. J. Jap. Soc. Food. Sci. Technol., 54: 304-309.

Kondjoyan, N. and J. L. Berdague. 1996. A Compilation of Relative Retention Indices

for the Analysis of Aromatic Compounds, editedby Laboratoire Flaveur, 1st

edn., INRA, Dijon, France.

Kondo, S., H. Yoshikawa and R. Katayama. 2004. Antioxidant activity in astringent

and non-astringent persimmons. J. Hort. Sci. Biotech., 79: 390–394.

337

Kozukue, N., T. Hironobu and M. Friedman. 2001. Tracer studies on the incorporation

of [2-14C]-DL-mevalonate into chlorophylls a and b, a-chaconine, and a-

solanine of potato sprouts. J.Agric.Food Chem., 49(1): 92–97.

Kumar, D., B. P. Singh and P. Kumar. 2004. An overview of the factors effecting

sugar content of potatoes. Ann. Appl. Biol., 145: 247-256.

Kumar, D., R. Ezekiel., B. Singh and I. Ahmed. 2005. Conversion table for specific

gravity, dry matter and starch content from under water weight of potatoes

grown in North Indian plains. Potato J., 32(1-2): 79-84.

Kyriacou, M. C., D. Gerasopoulos, A. S. Siomos and I. M. Ioannides. 2008. Impact of

hot water treatment on sprouting, membrane permeability, sugar content and

chip colour of reconditioned potato tubers following long-term cold storage. J.

Sci. Food Agric., 88 (15): 2682–2687.

Kyriacou, M. C., I. M. Ioannides, D. Gerasopoulos and A. S. Siomos. 2009. Storage

profile and processing potential of four potato (Solanum tuberosum .L)

cultivars under these storage temperature regimes. J. Food Agri. Env., 7(1):

31-37.

Lachman, J., K. Hamouz, M. Orsak and V. Pivec. 2001. Potato glycoalkaloids and

their significance in plant protection and nutrition. Rost. Vyr., 47: 181-1912.

Lachmann, J., K. Hamouz, M. Orsak and V. Pivec. 2000. Potato tubers as a significant

source of antioxidants in human nutrition. Rost. Vyr., 46: 231-236.

Lachmann, J., K. Hamouz., M. Orsak and V. Pivec. 2008. The influence of flesh

colour and growing locality on polyphenolic content and antioxidant activity in

potatoes. Sci. Hort., 117:109-114.

338

Larisch, B., Pischetsrieder, M and T. Severin. 1996. Reaction of dehydroascorbic acid

with primary aliphatic amines including N (alpha)-acethyllysine. J. Agric.

Food Chem., 44: 1630–1634.

Lee, K. R., N. Kozukue, J. S. Han, J. H. Park, E.Y. Chang and E. J. Baek. 2004.

Glycoalkaloids and metabolites inhibit the growth of human colon (HT29) and

liver (HepG2) cancer cells. J. Agric. Food Chem., 52: 2832–2839.

Lee, S. K and A. A. Kader. 2000. Preharvest and postharvest factors influencing

vitamin C content of horticultural crops. Postharvest Biol. Technol., 20: 207–

220.

Lefort, J. F., T. D. Durance and M. K. Upadhyaya. 2003. Effects of tuber storage and

cultivar on the quality of Vacuum Microwave-Dried (VMD) potato chips. J.

Food Sci., 68(2): 690-696.

Lejaa, M., A. Mareczeka and J. Benb. 2003. Antioxidant properties of two apple

cultivars during long-term storage. Food Chem., 80: 303–307.

Leonard, S. S., G. K. Harris and X. Shi. 2004. Metal-induced oxidative stress and

signal transduction. Free Radic. Biol. Med., 37:1921-1942

Leskova, E., J. Kubikova, E. Kovacikova, M. Kosicka, J. Porubska and K. Holcíkova.

2006. Vitamin losses: Retention during heat treatment and continual changes

expressed by mathematical models. J. Food Comp. Anal., 19 (4): 252-276.

Leszkowiat, M. J., V. Barichello, R. Y. Yada, R. H. Coffin, E. C. Lougheed, D. W.

Stanley. 1990. Contribution of sucrose to non enzymatic browning in potato

chips. J. Food Sci., 55, 281-282.

Lewis C. E., J. R. L. Walker, J. E. Lancaster and K. H. Sutton. 1998. Determination of

339

anthocyanins, flavonoids and phenolic acids in potatoes. I: Coloured cultivars

of Solanum tuberosum L. J. Sci. Food Agric., 77: 45–57.

Li, K. H., E. J. Park, H. S. Lee, D. M. Khu, S. L. Love and H.T. Lim. 2006. Evaluation

of Potato Varieties with High Antioxidant Activities by Measuring Phenolic

Acids in Different Tuber Parts. Hort. Environ. Biotechnol., 47(3):126−131.

Liu, M. S., Chen, R. Y., and Tsai, M. J. 1990. Effect of low-temperature storage,

gamma irradiation and iso-propyl-N-(3-chlorophenyl carbamate) treatment on

the processing quality of potatoes. J. Sci. Food Agric. 53: 1-13.

Liu, Q., E. Weber, V. Currie and R. Yada. 2003. Physicochemical properties of

starches during potato growth. Carbohydrate Polymers, 51: 213–221.

Loaiza, V. J. G. and M. E. Saltveit. 2001. Heat shock applied either before or after

wounding reduce browning of lettuce leaf tissue. J. Amer. Soc. Hort. Sci.,

126:227-234.

Love, S. L., T. Salaiz, B. Shafii, W.J. Price, A. R. Mosley and R. E. Thornton. 2004.

Stability of expression and concentration of ascorbic acid in North American

potato germplasm. Hort Sci., 39(1): 156-1 60.

Lusas, R. and L. Rooney. 2001. Snacks Foods Processing. Boca Raton: CRC Press

LLC.

Mackay, S. 1999. Techniques and types of fat used in deep-fat frying; A policy

statement and background paper prepared by Heart Foundation of New

Zealand.

Madhavi, D. L. and D. K. Salunkhe. 1998. Production, composition, storage and

340

processing. In: D. K. Salunkhe., S. S. Kadam. (Eds.), Tomato, Handbook of

Vegetable Science and Technology. Marcel Dekker, N. Y. pp.171-201.

Madiwale, G. P., L. Reddivari, D. G. Holm and J. Vanamala. 2011. Storage elevates

phenolic content and antioxidant activity but suppresses antiproliferative and

pro-apoptotic properties of colored-flesh potatoes against human colon cancer

cell lines. J. Agric. Food Chem., 59 (15): 8155–8166.

Mahajan B. V. C., A. S. Dhatt and K. S. Sandhu. 2005. Effect of different post harvest

treatments on the storage life of Kinnow. J. Food Sci. Technol., 42(4):269-299.

Makazan, Z., H. K. Saini and N. S. Dhalla. 2007. Role of oxidative stress in alterations

of mitochondrial function in ischemic-reperfused hearts. Am. J. Physiol. Heart

Circ. Physiol. 292: 1986-1994.

Malik, N. 1995. Potatoes in Pakistan: A Handbook. Pak-Swiss Potato Development

Project. Pak. Agric. Res. Council. Islamabad, Pakistan. p. 29

Mallikarjunan, P., M. S. Chinnan, V. M. Balasubramaniam and R. D. Phillips. 1997.

Edible coatings for deep-fat frying of starchy products. Lebensm-Wiss.

Technol., 30: 709–714.

Manach, C., A. Mazur, and A. Scalbert. 2005. Polyphenols and prevention of

cardiovascular diseases. Curr. Opin. Lipidol., 16: 77-84.

Manzano, J. E., Y. Perez and E. Rojas. 1997. Coating waxes on Haden mango fruits

(Mangifera indica L.) cultivar for export. Acta Hort. 455: 738-746.

Marchal, L. 1999. Towards a rational design of comercial maltodextrins a mechanistic

approach. Deuchtland: Tramper and Bergsma Eds.

Maria, P. F. 2007. Storage life enhancement of avocado fruits. (Diss). McGill

341

University. Department of Bioresource Engineering. McGill University. Ste-

Anne De Bellevue, QC., Canada.

Martin, F. L. and J. M. Ames. 2001. Formation of Strecker aldehydes and pyrazines in

a fried potato model system. J. Agric. Food Chem., 49: 3885-3892.

Martínez, R. D., F. Guillén, S. Castillo, P. J. Zapata, M. Serrano and D. Valero. 2008.

Development of a carbon-heat hybrid ethylene scrubber for fresh horticultural

produce storage purposes. Postharvest Biol. Technol., 55: 200-205.

Martinez, R. D., N. Alburquerque, J. M. Valverde, F. Guille´n, S.Castillo and D.

Valero. 2006. Postharvest sweet cherry quality and safety maintenance by Aloe

Vera treatment: a new edible coating. Postharvest Biol. Technol., 39: 93-100.

Mathooko, F. M. 1996. Regulation of respiratory metabolism in fruits and vegetables

by carbon dioxide. Postharvest Biol. Technol., 9 (3): 247-264.

Mattila, P and J. Hellström. 2007. Phenolic acids in potatoes, vegetables, and some of

their products. J. Food Comp. Anal., 20: 152–160.

McCann, L. C., P. C. Bethke and P. W. Simon. 2010. Extensive variation in fried chip

color and tuber composition in cold-stored tubers of wild potato (Solanum)

germplasm. J. Agric. Food Chem.., 58: 2368–2376.

Mehta, U. and B. Swinburn. 2001. A review of factor effecting fat absorption in hot

chips. Crit. Rev. Food Sci. Nutr., 41: 133-154.

Mellema, M. 2003. Mechanism and reduction of fat uptake in deep-fat fried foods. Tr.

Food Sci. Technol., 14: 364–373.

Mendoza, F., P. Dejmek and J. M. Aguilera. 2007. Colour and image texture analysis

342

in classification of commercial potato chips. Food Res. Intl., 40: 1146-1154.

Mensinga, T. T., A. J.A.M. Sips, C. J. M. Rompelberg, K. Twillert, J. Meulenbelt, H.

J. Top and H. P. Egmond. 2005. Potato glycoalkaloids and adverse effects in

humans:an ascending dose study. Regulatory Toxicol. and Pharmacol., 41: 66–

72.

Meredith R, 1995a. How sprout suppressants work. Potato Review, 5: 16.

Meredith R, 1995b. New chemical sets sprouts a challenge. Potato Review, 5: 10.

Messer, E. 2000. Potatoes(white) in Cambridge World History of Food, Vol.

1, ed. by Kiple KF and Ornelas K.C. Cambridge University Press,

Cambridge, UK. pp 187–200.

Mestdagh, F. J., T. Dewilde and K. Delporte. 2007. Impact of chemical pre-treatments

on the Acrylamide formation and sensorial quality of potato crisps, Food

Chem., 106: 914–922

Milde, J., E.F. Elstner and J. Grassmann. 2007. Synergistic effects of phenolics and

carotenoids on human low-density lipoprotein oxidation. Mol. Nutr. Food

Res., 51: 956-961.

Misra, J. B. and P. Chand. 1990. Relationship between potato-tuber size and chemical

composition. J. Food Sci. Technol., 27: 63-64.

Munoz, P. H., E. Almenar, M. Ocio and R. Gavara. 2006. Effect of calcium dips

and chitosan coating on post harvest life of strawberries (Fragaria

ananassa), J. Postharvest Biol. Technol., 39: 247-253.

Moore, E. D. and B. H. MacAnalley. 1995. A drink containing mucilaginous

343

polysaccharides and its preparation. U.S. Patent. 5: 443-830.

Moreira, R. G., M. E. Castell-Perez and M. A. Barrufet. 1999. Deep-Fat Frying:

Fundamentals and Applications. Gaithersburg, MD: Aspen Publishers.

Moretti, C. L., A. L Araujo, W. A. Marouelli and W. L. C. Silva. 2002. Respiratory

activity and browing of minimally processed sweet potatoes. Hortic. Bras., 20:

497-500.

Mottram, D. S., B. L. Wedzicha and A. T. Dodson. 2002. Acrylamide is formed in the

Maillard reaction. Nature, 419: 448-449.

Naczk, M. and F. Shahidi. 2004. Extraction and analysis of phenolics in food: A

review. J. Chromatog., 1054: 95-111.

Nakagawa, Y., K. Nakajima and T. Suzuki. 2004. Chloropharm induces mitochondrial

dysfunction in rat hepatocytes. Toxicol., 200: 123-133.

Nara, K., T. Miyoshi, T. Honma and H. Koga. 2006. Antioxidative activity of bound-

form phenolics in potato peel. Biosci. Biotechnol. Biochem., 70:1489–1491.

Nema, P. K, N. Ramaya., E. Duncan and K. Niranjan. 2008. Potato Glycoalkaloids:

formation and strategies for mitigation- A review. J. Sci. Food Agric., 88:

1869-1881.

Ni, Y., D. Turner, K. M. Yates and I. Tizard. 2004. Isolation and characterization of

structural components of Aloevera L. Leaf pulp. Intl. immunopharamacol., 4:

1745-1755.

Nicolas, J., F. C. Richard, P. M. Goupy, M. J. Amiot and S. Y. Aubert.1994.

Enzymatic browning reactions in apple and apple products. Crit. Rev. Food

Sci. Nutr., 34: 109-157.

344

Nielsen T. H., U. Deiting and M. A. Stilt. 1997. Amylase in potato tubers is induced

by storage at low temperature. Plant Physiol., 113(2): 503-510.

Niggeweg, R., A. J. Michael and C. Martin. 2004. Engineering plants with increased

level of the antioxidant chlorogenic acid. Nat. Biotechnol., 22: 746-754.

Nourian, F., H .S. Ramaswamy and A. C. Kushalappa. 2003. Kinetics of quality

change associated with the potatoes stored at different temperatures. Lebens-

Wiss Technol., 36: 49-65.

Nunes, M. C. N., J. P. Emond and J. K. Brecht. 2001. Temperature abuse during

ground and in flight handling operations affects quality of snap beans. Hort.

Sci., 36: 510.

Nzaramba, M. N., J. B. Bamberg, and J. C. Miller. 2007. Effect of propagule type and

growing environment on antioxidant activity and total phenolic content in

potato germplasm. Am. J. Potato Res., 84: 323-330

Olsson, K. 1996. Attempts to unveil potato clones disposed to stress induced

accumulation of glycoalkaloids in the field. Abstr European Association for

Potato Research, 13th Trienn Conf, Veldhoven, p. 538.

Olsson, M. E., J. Ekvall, K. E. Gustavsson, J. Nilsson, D. Pillai, I. Sjoholm, U.

Svensson, B. Akesson and M. G. L. Nyman. 2004. Antioxidants, low

molecular weight carbohydrates, and total antioxidant capacity in strawberries

(Fragaria ananassa): effects of cultivar, ripening, and storage. J. Agric. Food

Chem., 52: 2490–2498.

Oosterhaven, K., B. Poolman and E. J. Smid. 1995. S-carvone as a natural potato sprout

345

inhibiting, fungistatic and bacteristatic compound. Industrial Crops

Products, 4: 23-31.

Ozkan, M., A. E. Kırca and B. Cemero. 2004. Effects of hydrogen peroxide on the

stability of ascorbic acid during storage in various fruit juices. Food Chem.,

8(4): 591-597.

Padayatty, S. J., A. Katz, Y. Wang, P. Eck, O. Kwon, J. H. Lee, S. Chen, C. Corpe, A.

Dutta, S. K. Dutta and M. Levine. 2003. Vitamin C as an Antioxidant:

Evaluation of Its Role in Disease Prevention J. Am. College Nutr., 22(1):18–

35.

Padda, M. S. and D. H. Picha. 2008. Effect of low temperature storage on phenolic

composition activity of sweet potatoes. Postharvest Biol. Technol., 47:176–180.

PHDEB (Pakistan Horticulture Development and Export Board). 2008. Potato

Marketing Strategy. pp. 29.

Pandey, P.C., S. V. Singh, S. K. Pandey, B. W. Singh. 2007. Dormancy, sprouting

behavior and weight loss in Indian potato (Solanum tuberosum) varieties. Ind.

J. Agric. Sci., 77(11): 715-720.

Papathanasiou F, S. H. Mitchell and B. Harvey. 1999. Variation in glycoalkaloid

amount of potato tubers harvested from mature plants. J. Sci. Food Agric.,

79(1):32–36.

Patel, B., R. Schutte, P. Sporns, J. Doyle, L. Jewel and R. N. Fedorak. 2002. Potato

glycoalkaloids adversely aVect intestinal permeability and aggravate

inXammatory bowel disease. In Xamm. Bowel Diss. 8:340–346.

Pavlista, A. D., J. C. Ojala. 1997. Potatoes: Chips and French fry processing. In

346

Processing Vegetables-Science and Technology. Eds. D.S. Smith, J. N. Cash,

W. Nip and Y. H. Hui. Lancaster, USA: Technomac Publishing Co. pp. 287-

284.

Pavlista, A. 2001. Green Potatoes: the Problem and the Solution. Neb Guide online:

G01-1437-A.

Pedreschi, F. and P. Moyano. 2005. Effect of pre-drying on texture and oiluptake of

potato chips. Lebensm-Wiss Technol., 38: 599-604.

Pedreschi, F., K. Kaack, and K. Granby. 2004. Reduction of acrylamide formation in

potato slices during frying. Lebensm-Wiss Technol., 37: 679- 685.

Pedreschi, F., J. M. Aguilera and L. Pyle. 2001. Textural characterization and

kinetics of potato strips during frying. J. Food Sci., 66: 314–318.

Peksa, A., G. Golubowska, K. Aniolowski, G. Lisinska and E. Rytel. 2006. Changes in

glycoalkaloids and nitrate contents in potato during chip processing. Food

Chem., 97:151-156.

Percival, G. 1999. Light-induced glycoalkaloid accumulation of potato tubers

(Solanum tuberosum L) J. Sci. Food Agric., 79(10):1305-1310.

Percival, G. C., J. A. C. Harrison and G. R. Dixon. 1993. The influence of

temperature on light enhanced glycoalkaloid synthesis in potato. Ann.

Appl. Biol., 123:141–153.

Percival, G.C., G. R. Dixon and A. Sword. 1994. Glycoalkaloid concentration

of potato tubers following continuous illumination. J. Sci. Food Agric.,

66:139–144.

PIC (Potato International Centre). 2008. Potato: Growth in production Accelerates.

347

Accessed at: http://www.cipotato.org/potato/facts. Propotato

(www.Potatopro.com)<Date accessed 07/07/2010>

Piga, A., M. Agabbio, F. Gambella and M. C. Nicoli. 2002. Retention of antioxidant

activity in minimally processed mandarin and Satsuma fruits. Lebensm-Wiss

Technol., 35: 344–347.

Pinthus, E. J., P. Weinberg and I. S. Saguy. 1995. Oil uptake in deep fat frying as

affected by porosity. J. Food Sci., 60: 767-769.

Plhak, L. C. and P. Sporns. 1992. Enzyme immunoassay for potato

glycoalkaloids. J. Agric. Food Chem., 40:2533–2540.

Poli, G., G. Leonarduzzi, F. Biasi and E. Chiarpotto. 2004. Oxidative stress and cell

signalling. Curr. Med. Chem., 11:1163-1182.

Raban A., A. Tagliabue, N. J. Christensen, J. Madsen, J. J. Host and A. Astrup. 1994.

Resistant starch: the effect on postprandial glycemia, hormonal response, and

satiety. Am. J. Clin. Nutr., 60: 544-551.

Raghami, N. 2009. Distinction of defected potatoes via ultra sonic. Thesis MSc.

Shahrekord University, pp: 49-55.

Rajendran, S. and V. Sriranjini. 2008. Plant products as fumigants for stored-product

insect control. J. Stored Products Res., 44: 126-35.

Rakotonirainy, A. M., Q. Wang and G. W. Padua. 2001. Evaluation of zein films as

modified atmosphere packaging for fresh broccoli. J. Food Sci., 66:1108-1111.

Ranganna, B. G. S. V. Raghavan and A. C. Kushalappa. 1998. Hot water dipping to

enhance storability of potatoes. Postharvest Biol. Technol., 13: 215–223.

348

Rayner, M., V. Ciolfi, B. Maves, P. Stedman and G. S. Mittal. 2000. Development and

application of soy-protein films to reduce fat intake in deep-fried foods. J. Sci.

Food Agric., 80: 777 –782.

Reyes, L. F. and L. C. Zevallos. 2003. Wounding stress increases the phenolic content

and antioxidant capacity of purple-flesh potatoes (Solanum tuberosum L.). J.

Agric. Food Chem., 51: 5296-5300.

Reyes, L. F., J. C. Miller Jr. and L. C. Zevallos. 2005. Antioxidant capacity,

anthocyanins and total phenolics in purple- and red-fleshed potato (Solanum

tuberosum L.) genotypes. Am. J. Potato Res., 82: 271-277.

Reynolds, T. and A.C. Dweck. 1999. Aloe vera leaf gel: a review update. J.

Ethnopharmacol., 68: 3–37.

Rimac, B. S., V. Lelas, D. Rade and B. Simundic. 2004. Decreasing of oil absorption

in potato strips during deep fat frying. J. Food Engin., 64: 237-241.

Rita, M. D., M. Machado, C. F. Toledo and C.G. Lucila. 2007. Effect of light

and temperature on the formation of glycoalkaloids in potato tubers.

Food Control, 1 8 : 503–508.

Rivero, R. C., E. R. Rodriguez and C. D. Romero. 2003. Effects of current storage

conditions on nutrient retention in several varieties of potatoes from Tenerife.

Food Chem., 80: 445–450.

Robbins, R. J. 2003. Phenolic acids in foods: an overview of analytical methodology.

J. Agric. Food Chem., 51: 2886-2887.

Robert, C., F. Soliva and O. B. Martın. 2003. New advances in extending the shelf life

of fresh-cut fruits: a review. Trends Food Sci. Technol., 14: 341–353.

349

Rodriguez, S. L. and R. Wrolstad. 1997. Influence of potato composition on chip color

quality. Am. Potato J., 74: 87-106.

Rodriguez, L. J. N., L. G. Fenoll, C. Devece, D. S. Hernandez, E. D. L. Reyes, F. G.

Canovas. 1999. Thermal inactivation of mushroom polyphenoloxidase

employing 2450 MHz microwave radiation. J. Agric. Food Chem., 47:3028–

3035.

Rodriguez, S. L. E., R. E. Wrolstad and C. Pereira. 1999. Glycoalkaloid content and

anthocyanin stability to alkaline treatment of red-fleshed potato extracts. J.

Food Sci., 64(3): 445–450.

Rojas, G. M. A., R. S. Fortuny and O. M. Belloso. 2007. Effect of Natural

Antibrowning Agents on Color and Related Enzymes in Fresh-Cut Fuji Apples

as an Alternative to the Use of Ascorbic Acid. J. Food Sci., 72(1): 36-43.

Rosenfeld, H. J., H. A. Sundell, P. Lea and M. Ringstad.1995. Influence of packaging

materials and temperature on the glycoalkaloid content of potato tubers. Food Res.

Intl., 28(5):148-184 .

Rytel, E., G. Golubowska, G. Lisińska, A. Pęksa and K. Aniolowski. 2005. Changes in

glycoalkaloid and nitrate contents in potatoes during French fries processing. J.

Sci. Food Agric., 85: 879-882.

Ishaq, S., H. A. Rathore, T. Masud and S. Ali. 2009. Influence of Post Harvest

Calcium Chloride Application, Ethylene Absorbent and Modified Atmosphere

on Quality Characteristics and Shelf Life of Apricot (Prunus armeniaca L.)

Fruit During Storage. Pak. J. Nutr., 8 (6): 861-865.

Saammi, S. and T. Masud. 2007. Effect of different packaging systems on storage life

350

and quality of tomato (lycopersicon esculentum var. rio grande) during

different ripening stages. Intl. J. Food Safety, 9: 37-40.

Saari, N. B., S. Fujita, R. Miyazoe and M. Okugawa. 1995. Distribution of ascorbate

oxidase activities in the fruits of family cucurbitaceae and some of their

properties. J. Food Biochem., 19: 321–327.

Saks, Y. and R. G. Barkai. 1995. Aloe Vera gel against plant pathogenic fungi.


Saltveit, M. E. 2000. Wound induced changes in phenolic metabolism and tissue

browing are alterad by heat shock. Postharvest Biol. Technol., 21: 61-69.

Salunkhe, D. K. and B. B. Desai. 1984. Post Harvest Biotechnology of Vegetables. 2nd

ed., CRC Press. Boca Raton, Florida, US, pp. 55-82.

Sanchez, M. C., M. Camara and C. Dıez-Marques. 2003. Extending shelf-life and

nutritive value of green beans (Phaseolus vulgaris L.) by controlled

atmosphere storage: macronutrients. Food Chem., 80: 309–315.

Sangwan, N. S., A. H. A. Farooqi, F. Shabih and R. S. Sangwan. 2001. Regulation of

essential oil production in plants. Plant Growth Regulation, 34: 3-21.

Saraiva, J. A., I. M. Rodriques. 2011. Inhibition of tuber sprouting by pressure

treatments.Intl. J. Food Sci. Technol., 46 (1): 61-66.

Scandalios, J. G. 1993. Regulation and properties of plant catalases. In: C. Foyer and

P Mullineaux (Editors), Photooxidative Stress in Plants. CRC Press, Boca

Raton, Fla., pp. 275-315.

Schroeter, H., C. Boyd, J. P. Spencer, R. J. Williams, E. Cadenas, and C. Rice-Evans.

351

2002. MAPK signaling in neurodegeneration: Influences of flavonoids and of

nitric oxide. Neurobiol. Aging, 23: 861-880.

Seeram, N. P., L. S. Adams, S. M. Henning, Y. Niu, Y. Zhang, M. G. Nair and D.

Heber. 2005. In vitro antiproliferative, apoptotic and antioxidant activities of

punicalagin, ellagic acid and a total pomegranate tannin extract are enhanced

in combination with other polyphenols as found in pomegranate juice. J. Nutr.

Biochem., 16: 360-367.

Segnini, P., P. Dejmek and R. Oste. 1999. A low cost video technique for colour

measurement of potato chips. Swiss Society Food Sci. Technol., 32: 216-222.

Sengul M., F. Keles and M. S. Keles. 2004. The effect of storage conditions

(temperature, light, time) and variety on the glycoalkaloid content of potato

tubers and sprouts. Food Control, 15: 281–286.

Setha, S., S. Kanlayanarat and V. Srilaong. 2000. Changes in Polyamine levels and

peroxidase activity in “Khakdun” papaya (Carica papaya L.) under low

temperature storage conditions. In: Quality Assurance in Agricultural

Produce, Ed. G. I. Johnson, LeVan To, N. D. Duc, M. C. Webb. ACCIAR

Proceedings, 100: 593–598.

SFA (Snack Food Association).1991. Potato Composition Guide. Wheaton:

American Slide-Chart Corp.

Shabana M.M., M.A.A. El-Fattah and S.A. Shehata. 1987. The effects of storage on

solanine concentration in the potato tubers. Egypt. J. Hortic., 14:137–142.

Shahidi, F. 2002. Antioxidants in plants and oleaginous seeds, In: M.J. Morello, F.

352

Shahidi, and T.C. Ho (eds.). Free radicals in food: Chemistry, nutrition, and

health effects. Am. Chem. Soc., Washington, DC. pp. 162-175.

Shahidi, F. and M. Naczk. 1995. Food phenolic: An overview, p. 1-5. In: F. Shahidi

and M. Naczk (eds.). Food phenolics: Sources, chemistry, effects, applications.

Technomic Publishing Co., Lancaster, PA.

Singh, G., I. P. S. Kapoor and S. K. Pandey. 1997. Studies on essential oils. Part 7.

Natural sprout inhibitors for potatoes. Pesticide Res. J., 9: 121-124.

Singh, J., O. J. McCarthy, H. Singh and P. J. Moughan. 2008. Low temperature post-

harvest storage of New Zealand Taewa (Maori potato): Effects on starch

physico-chemical and functional characteristics. Food Chem., 106: 583–596.

Singh, N and P. S. Rajini. 2004. Free radical scavenging activity of an aqueous extract

of potato peel. Food Chem., 85: 611-616.

Sinha, N. K., J. N. Cash and R. W. Chase. 1992. Differences in sugar, chip color,

specific gravity and yield of selected potato cultivars grown in Michigan. Am.

Potato J., 69: 385-389.

Slanina, P. 1990. Solanine (glycoalkaloids) in potatoes: toxicological evaluation. Food

Chem. Toxicol., 28(11): 759-761.

Smith, C., T. Perfetti, M. Rumple, A. Rodgman and D. Doolittle. 2000. “IARC group

2A carcinogens” reported in cigarette mainstream smoke. Food Chem.

Toxicol., 38: 371-383.

Smith, D. B., J. G. Roddick and J. L. Jones. 1996. Potato glycoalkaloids: some

unanswered questions. Trends Food Sci. Technol., 7:126–131.

353

Song, X . 2009. The impact of dill weed, spearmint and clove essential oils on sprout

suppresion in potato tubers. Am. J. Potato Res., 86 ( 4): 278-285.

Sonia, Z. V. and A. R. Chaves. 2006. Antioxidant responses in minimally processed

celery during refrigerated storage. Food Chem., 94: 68–74.

Sonnewald U. 2001. Control of potato tuber sprouting. Trends Plant Sci., 6: 333-335.

Sowokinos J R. 2001. Allele and isozyme patterns of UDPglucose pyrophosphorylase

as a marker for cold-sweetening resistance in potato. Am. J. Potato Res., 78:

57-64.

Sowokinos, J. R. 1990. Stress induced alteration in carbohydrate metabolism. In: The

Molecular and Cellular Biol. Potato, M E Vayda and W D Park (Eds.)

Wallingford, UK: CAB International. pp. 137-158.

Srinivasa, P. C., K. V. H. Prashanth, N. S. Susheelamma, R. Ravi and R. N.

Tharanathan. 2006. Storage studies of tomato and bell pepper using eco-

friendly films. J. Sci. Food Agric., 86: 1216-1224.

Srinivasa, P.C. and R. N. Tharanathan. 2007. Chitin/Chitosan-Safe, Eco-friendly

Packaging Materials with Multiple Potential Uses. Food Rev. Intl., 23: 53–72.

Stadler, R. H., I. Blank, N. Varga, F. Robert, J. Hau, P. A. Guy, M. C. Robert and S.

Riediker. 2002. Acrylamide from Maillard reaction products. Nature, 419: 449-

450.

Steel, R. D., J. H. Torrie and D. Dickey. 1997. Principle and Procedure of Statistics. A

Biometrical approach: 3rd Ed. McGraw-Hills Book Co. Inc. New York

Subramanian, N., P. Venkatesh, S. Ganguli and V. P. Sinkar. 1999. Role of polyphenol

354

oxidase and peroxidase in the generation of black tea theaflavins. J. Agric.

Food Chem., 47: 2571- 2578.

Suttle, J. C. 2007. Dormancy and sprouting. In: Potato biology and biotechnology,

Vreugdenhil, D. & Bradshaw, J. (Eds.). Amsterdam: Elsevier Science B.V.

Svensson, K., L. Abramsson, W. Becker, A. Glynn, K. E. Hellenas, Y. Lind and J.

Rosen. 2003. Dietary intake of acrylamide in Sweden. Food Chem. Toxicol.,

41: 1581-1586.

Tamaki, D. S., H. J. Ichi and I. Kazuhiko. 2003. Effects of Low Temperature Storage

on the Quality of Different Processing Cultivars of Potato Tubers. Food Pres.

Sci., 29(5): 275-279.

Tareke E, P. Rydberg, P. Karlsson, S. Ericksson and M. Tornqvist. 2002. Analyses of

acrylamide, a carcinogen formed in heated foodstuffs. J. Agric. Food Chem.,

50: 4998-5006.

Tawfik, A. A., S. A. Mansour, H. M. Ramadan and A. N. Fayad. 2002. Processing

quality of selected potato varieties for chip and French fry industries in Egypt.

Afric. Crop Sci. J., 10(4): 325-333.

Teixeira, S., C. Siquet, C. Alves, I. Boal, M. P. Marques, F. Borges, J. L. Lima, and S.

Reis. 2005. Structure-property studies on the antioxidant activity of flavonoids

present in diet. Free Radic. Biol. Med., 39: 1099-1108.

Tester, R. F., R. Ansell, C. E.Snape and M. Yusuph. 2005. Effect of storage

temperatures and annealing conditions on the structure and properties of potato

(Solanum tuberosum) starch. Intl. J. Biol. Macromol., 36: 1-8.

Tian, S. P. A. L. Jiang, Y. Xu and Y. S. Wang. 2004. Responses of physiology and

355

quality of sweet cherry fruit to different atmospheres in storage. Food Chem.,

87: 43–49.

Toit, R. D., Y. Volsteedt and Z. Apostolides. 2001. Comparison of the antioxidant

content of fruits, vegetables and teas measured as vitamin C equivalents.

Toxicol., 166: 63–69.

Tsouvaltzis, P., A. Deltsidis and J. K. Brecht. 2011. Hot Water Treatment and Pre-

processing Storage Reduce Browning Development in Fresh-cut Potato Slices.

Hort. Sci., 46(9): 1282-1286.

Tuil, R.V., P. Fowler, M. Lawthe and C. J. Weber. 2000. Properties of Biobased

Packaging Materials. In Biobased Packaging Materials for the Food Industry.

Status and Perspective; Weber, C.J. Ed. The Royal Veterinary and Agriculture

University: Frederiksberg C, Denmark. pp: 20–26.

USDA. 2002. Agricultural Statistics. Washington, D.C.: United States Department of

Agriculture. U.S. Environmental Protection Agency (date accessed: 10 Dec,

2010). Consumer facts on acrylamide. http://www.epa.gov/safewater/dwh/c-

voc/acrylami.html

Valko, M., H. Morris, M. Mazur, P. Rapta and R. F. Bilton. 2001. Oxygen free radical

generating mechanisms in the colon: Do the semiquinones of vitamin K play a

role in the aetiology of colon cancer? Biochem. Biophys. Acta, (1527): 161-

166.

Valkonen, J. P. T., M. Keskitalo, T. Vasara and L. Pietila. 1996. Potato glycoalkaloids:

a burden or a blessing. Crit. Rev. Plant Sci., 15:1–20

Valverde, J. M., D. Valero, D. M. Omero, F. Guillean, S. Castillo and M. Serrano.

356

2005. Novel edible coating based on aloe vera gel to maintain table grape

quality and safety. J. Agric. Food Chem., 53: 7807-7813.

Vanes, A. and K. J. Hartmans. 1987. Starch and sugars during tuberization, storage

and sprouting. In A. Rastovski and A. Vanes (Eds.), Storage of potatoes.

Pudoc: Wageningen. pp. 114–132.

Vattem, D.A. and K. Shetty. 2003. Acrylamide in food: a model for mechanism of

formation and its reduction. Innov. Food Sci. Emer. Technol., 4: 331- 338.

Vaughn S. F. and G. F. Spencer. 1991. Volatile monoterpenes inhibit potato tuber

sprouting. Am. Potato J., 68: 821-831.

Vaughn, S. F. and G. F. Spencer. 1993. Naturally-occurring aromatic compounds inhibit

potato tuber sprouting. Am. Potato J., 70: 527-33.

Vela, G., D.M. Leon, H.S. Garcia and J.D. C. Unida. 2003. Polyphenoloxidase activity

during ripening and chilling stress in ‘Manila’ mangoes. J. Hort. Sci. Biotechnol.,

78: 104-107.

Velioglu, Y. S., G. Mazza, L. Gao and B. D. Oomah. 1998. Antioxidant activity and

total phenolics in selected fruits, vegetables, and grain products. J. Agric. Food

Chem., 46: 4113-4117.

Vinson, J. A., Y. Hao, X. Su and L. Zubik. 1998. Phenol antioxidant quantity and

quality in foods: vegetables. J. Agric. Food Chem., 46:3630–3634.

Vitti, M. C. D., F. F. Sasaki, P. Miguel1, R. A. Kluge and C. L. Moretti. 2011. Activity

of Enzymes Associated with the Enzymatic Browning of Minimally Processed

Potatoes. Braz. archives Technol., 54 (5): 983-990.

Vokou, D., S. Vareltzidou and P. Katinakis. 1993. Effects of aromatic plants on potato

357

storage - sprout suppression and antimicrobial activity. Agric. Ecosystems

Environ., 47: 223-35.

Vorne, V., K. Ojanpera, L. D. Temmerman, M. Bindi, P. Hoggy and M. Jones. 2002.

Effects of elevated carbondioxide and ozone on potato tuber quality in the

Europeon multiple sites experiment “CHIP- project”. Eur. J. Agron., 17(4):

369-381.

Walingo A, J.N. Kabira, H.M. Kidanemariam and P.T. Ewell. 1995. Evaluating potato

clones under seed and ware storage conditions at Tigoni- Kenya, Proceedings

of the Triennial Symposium, International Society for Root Crops (ISTRc )-

AB Lilongwe, Malawi. pp. 515-579.

Walker, J. R. L. 1995. Enzymatic browning in fruits: Its biochemistry and control. In:

Enzymatic Browning and its Prevention, C.Y. Lee and J.R. Whitaker (Eds.),

ACS Symp. Ser. 600, Washington, D.C. p. 8-22.

Warner, K., P. Orr and M. Glynn. 1997. Effect of Fatty Acid Composition on Flavor

and Stability of Fried Foods. J. Am. Oil. Chem. Soc., 74: 347–356.

Weng Y. M and M. J. Chen. 1997. Sorbic Anhydride as Antimycotic Additive in

Polyethylene Food Packaging Films. Lebensm-Wiss Technol., 30: 485–487.

Western Potato Council, 2003. Guide to Commercial Potato Production on the

Canadian Prairies. Winnipeg: Western Potato Council.

Williams, R. and G. S. Mittal. 1999. Water and fat transfer properties of

polysaccharide films on fried pastry mix. Food Sci. Technol., 32: 440–445.

Wiltshire, J. J. and A. H. Cobb. 1996. A review of the physiology of potato tuber

dormancy. Annals Appl. Biol., 129: 553-569.

Woolfe, J.A. 1987. The Potato in the Human Diet. Cambridge University Press,

358

New York. Published in collaboration with International Potato Center,

Peru.

Yemeicioglu, A. 2002. Control of polyphenol oxidase in whole potatoes by low

temperature blanching. Eur.Food Res. Technol., 214: 313-319.

Yilmaz, G., M. Tuzen, N. Kandemir, D. Mendil and H. Sari. 2005. Trace metal levels

in some modern cultivars and Turkish landraces of potato. Asian J. Chem., 17:

79-84.

Zhou D and Solomos T. 1998. Effect of hypoxia on sugar accumulation, respiration,

activities of amylase and starch phosphorylase, and induction of alternative

oxidase and acid invertase during storage of potato tubers (Solanum tuberosum

cv. Russet Burbank) at 1°C. Physiol. Plantarum, 104: 255- 265.

Zoffoli, J. P., J. Rodriguez, P. Aldunce and C. H. Crisosto. 1997. Development of high

concentration carbon dioxide modified atmosphere packaging systems to

maintain peach quality. Postharvest Hortic. Ser., 3: 37–45.

Zorzella, C. A., J. L. S. Vendruscolo, R. O. Treptow and T. L Almeida. 2003.

Caracterização física, químicae sensorial de genótipos de batata processados

na forma de chips. Braz. J. Food Technol., 6: 15-24.

Zrust, J., V. Horackova, V. Prichystalova and M. Rejlkova. 2001. Light-induced

α-chaconine and α-solanine accumulation in potato tubers (Solanum

tuberosum L.) after harvest. Rost. Vyr., 47:469–474.

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