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MODIFIED ATMOSPHERE PACKAGING OF READY TO COOK IDLI

BATTER

THESIS

Submitted to the Pondicherry University

for the award of the degree

DOCTOR OF PHILOSOPHY

In

FOOD SCIENCE AND NUTRITION

By

M. DURGADEVI

DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY

PONDICHERRY UNIVERSITY

PUDUCHERRY-605 014

DECEMBER – 2011

Dr. H. PrathapKumar Shetty

Reader and Head (i/c)

CERTIFICATE

This is to certify that this thesis entitled “Modified atmosphere packaging of

ready to cook idli batter” is a record of research work done by the candidate, Miss.

M. Durgadevi, during the period of her study in the Department of Food Science and

Technology, Pondicherry University, Puducherry under my supervision. This

research work has not previously been formed the basis for award of any degree,

diploma, associateship or fellowship or any other similar title and that it represents

entirely an independent work of the candidate.

Signature of Guide Signature of H.O.D

Signature of Dean

R.V. Nagar, Kalapet, Puducherry- 605 014, India

Pondicherry University

Department of Food Science and Technology

Ms. M. Durgadevi

Department of food Science and Technology

Pondicherry University

Puducherry-605 014

DECLARATION

I hereby declare that the thesis entitled “Modified atmosphere packaging of

ready to cook idli batter” submitted to Pondicherry University in partial fulfillment

of the requirement for the award of Doctor of Philosophy in Food Science and

Nutrition, is my original work and has not been previously formed the basis for

award of any degree, diploma, associateship, fellowship or any other similar title.

Puducherry

Date: (M. Durgadevi)

ACKNOWLEDGEMENT

I express my humble gratitude to the Vice Chancellor, Pondicherry

University, Dr. J.A.K.Tareen for granting me permission to carry out my research

work in the Department of Food Science and Technology, Pondicherry University as

the first Scholar of the department.

I express my thanks to Dean of Life Sciences, Dr. P.P.Mathur for providing

all necessary facilities to the Department to carry out my research.

I express my profound gratitude to my supervisor Dr. H. PrathapKumar

Shetty, Reader and Head (i/c), Department of Food Science and Technology,

Pondicherry University who explored in me the art of doing research and helped me

advance in my independent thinking. I appreciate the freedom given to me

throughout the research period and the ceaseless and dynamic guidance. I also thank

him for the necessary facilities and arrangements provided to carry out my research

successfully.

I thank my Doctoral committee members Dr. Jeevarathinam (Head,

Department of Microbiology) and Dr. Shakthivel (Head, Department of

Biotechnology) for providing valuable suggestions and constructive criticism on my

work.

I would like to express my gratefulness to my Doctoral committee member

Dr. John Don Bosco, Reader Department of Food Science and Technology for his

guidance, granting permission to operate the equipments in his Product

Development Lab. I also thank him for his moral support and encouragement to

complete my work successfully.

I am happy to thank Dr. Narayanasamy Sangeetha, Assistant Professor,

Department of Food Science and Technology for her continuous support, and for

granting permission to carry out my experiments in Food and Nutrition lab.

I sincerely thank Dr. S.Hari priya, Assistant Professor, Department of Food

Science and Technology for her valuable suggestions and comments on my work

progress and for helping me throughout the study period.

I thank Dr. K.V.Sunooj, Assistant Professor, Department of Food Science

and Technology for motivating me throughout the study period and helping me in

operating texture analyzer.

I express my sincere gratitude to Dr. R.Ravi, Department of Sensory

Sciences, CFTRI, for guiding me in statistical analysis, for making himself available

to clarify all queries whenever required, for the patience shown towards my work

progress and for supporting me to complete the study successfully.

I express my gratitude to Dr. Vishnuvardhan, Assistant Professor,

Department of Statistics, Pondicherry University and Miss. Anusuya, guest lecturer,

Department of Food Science and technology for supporting my study with statistical

guidance.

I thank my non-teaching staffs Mrs. Gomathi, Mr. Chakravarthy, Mrs.

Kolanchiammal, Miss. Chandra, Mrs. Valliammal, and Mr. Angappin for helping

me with the needed amenities.

I thank Dr. Sundar for inspiration and guidance given to carry out my

research.

I thank all my colleagues S. Uma Maheswari, D. Sumitha, C.Saravanan,

Sanjay Prathap Singh, P. Vasanthakumari, M. Pushpadevi, M. Shakthi

Kandamoorthy, K.Devi, S.J.Cynthia, Soumya Bhol, Ravindra Kumar Agarwal,

Ch.Koteeswara Reddy, Shabir and P.Vandarkuzhali, for their help rendered during

my research period and for the moral support given.

I also thank research assistants Santhalakshmi and Venkadesaperumal for

their timely help.

I thank to Dr. Kumari who encouraged me to do my research work at

Pondicherry University. I thank Dr. Saraswathi, Dr. K.S. Pushpa, Dr. S.S.

Vijayanchali and Mrs. Kavitha Mythili, Mr. Devanarayanan, Dr. C. K. Venil for

their encouragement.

I express my sincere thanks to University Grants Commission for providing

me Junior Research Fellowship without which I must not have carried out my

research work. I express my thanks to Tamil Nadu Rice Research Institute, TNAU,

and Aduthurai for providing me ADT3 variety black gram dhal throughout my study

period. I also express my thanks to SID, IISc, Bangalore for helping me to carry out

LC-MS analysis for my samples.

I thank all the respondents of my study who patiently supported my survey.

I thank Dr.Victor Anand raj and family, Dr. Bhusan Sudhakar and family,

Dr. Vellari and family, Dr.Shiva Sankar and family, Dr. Tokozu and family,

Dr.Sherry and family, Dr.Hannah Rachael Vasanthi, Dr.Rejena, Anandh uncle, Rena

aunty, Ellan anna, Sujitha akka, Pastor Kima, Deepa aunty and family, Phelix uncle

and family and all PUCF friends for encouraging my research work through prayers

and for the care shown in my personal life.

My special thanks to my dear friends Sharen Elizabeth Thomas, Gita, Aliza

Princy, Ithayamalar, Venkataramaiah, Murali, Srikanth, Ravindra, Ramachitra and

family, Shanmuga Sundari, Indhumathi, Kayalvizhi, Suman, Rajinish, Vijaya

Bharathy, Vikram, Vinayagam, Mayilvaganan, Supriya, Maya and Vijayalakshmi

for their continuous support to carry out my work.

My humble thanks to my parents Mr.R.Manoharan and Mrs.M.Janaki , my

sister Mrs.M.Ahiladevi, brother-in-law Mr.J.Arokiaraj, my brother Mr. M. Prasanna

Venkateshwaran, my sister-in-law Mrs.Jothi , my niece Baby. A. Thilaka Catheriene

and Mr. K. Durga Prasad and family for all moral support, financial assistance, love,

care, and encouragement showered on me throughout my study period.

Above all, I owe my humble gratefulness and faithfulness to my Lord

Almighty for His continuous grace and blessings to finish my research work

successfully.

ABBREVATIONS

ADT3 - Aduthurai

ANOVA - Analysis of Variance

BMI - Body Mass Index

BV - Biological Value

CA - Controlled Atmosphere

CCRD - Central Component Rotatable design

DC - Digestibility Co-efficient

FAA - Free Amino Acids

FAN - Free α-amino Nitrogen

FER - Feed Efficiency Ratio

FOS - Fructo-oligosaccharide

HM - High Molecule

HUDCO - Housing and Urban Development Corporation

IR20 - International Rice 20

LCMS - Liquid Chromatography Mass Spectrometry

LDPE - Low Density Poly Ethylene

MAP - Modified Atmosphere Packaging

MS - Mild Steel

NDOs - Non Digestible oligosaccharides

NPU - Net Protein Utilization

NSP - Non Starch polysaccharides

PCA - Principal Component Analysis

PER - Protein Efficiency Ratio

PP - Poly Propylene

QDA - Quantitative Descriptive Analysis

RA - Relative abundance

RPER - Relative Protein Efficiency Ratio

RSM - Response Surface Methodology

SCFA - Short Chain fatty Acid

TAG - Triacylglycerol

TPA - Texture Profile Analysis

VLDL - Very Low density Lipoprotein

WHO - World Health Organization

v/v - volume/volume

w/w - weight/weight

h - Hour

Pa - Pascal

mm - Milli meter

mL - Milli liter

g - Gram

µL -Micro liter

N - Newton

N s - Newton second

CONTENTS

1 Introduction and review of literature 1

1.1 Introduction 1

1.2 Review of literature 2

1.2.1 Significance of fermented foods 2

1.2.2 Positive health outcomes of breakfast consumption 4

1.2.3 Idli and its properties 5

1.2.3.1 Nutritional composition of idli 5

1.2.3.2 Physico- chemical parameters of idli 6

1.2.4 Rice - a staple food grain in idli making 9

1.2.5 Black gram- a protein source in idli making 12

1.2.6 Oligosaccharides in foods 13

1.2.6.1 Conversion of polysaccharides into oligosaccharides 14

1.2.6.2 Physiological properties of oligosaccharides 14

1.2.6.3 Animal studies on oligosaccharides 17

1.2.6.4 Applications of FOS in food formulations 18

1.2.7 Modified atmosphere packaging 18

2

Transition in the preparation and consumption of idli among the

population of Puducherry

23

2.1 Introduction 23

2.2 Materials and Methods 23

2.2.1 Selection of area 23

2.2.2 Selection of tool for data collection 24

2.2.3 Selection of respondents 24

2.2.4 Data analysis 24

2.3 Results and discussion 24

2.3.1 Socio-economic profile of the selected respondents 24

2.3.2 Consumption pattern of breakfast among the selected respondents 27

2.3.3 Preparation of idli at household level 29

2.3.4 Preference for commercial idli batter against home-made batter 33

2.4 Conclusion 35

3

Texture optimization of idli

36

3.1 Introduction 36

3.2 Materials and methods 38

3.2.1 Materials 38

3.2.2 Preparation of idli 38

3.2.3 Experimental design 38

3.2.3.1 Response surface methodology 38

3.2.3.2 Optimization of idli 40

3.2.3.3 Instrumental color measurement 40

3.2.3.4 Texture profile analysis (TPA) 41

3.2.4 Statistical analysis 45


3.3.1 Effect of rice varieties on rice batter volume 45

3.3.2 Effect of black gram on batter volume 46

3.3.3 Effect of ratios of rice to black gram dhal on batter volume 47

3.3.4 Response surfaces 50

3.3.5 Instrumental color measurement of idli 50

3.3.6 Texture parameters 54

3.3.7 Simultaneous optimization 63

3.4 Conclusion 64

4

Process optimization of idli using sensory attributes

65

4.1 Introduction 65


4.2.1 Materials 66

4.2.2 Preparation of idli 66

4.2.3 Experimental design 67

4.2.3.1 Response surface methodology 67

4.2.3.2 Optimization of idli using RSM 67

4.2.3.3 Sensory analysis of idli 68

4.2.3.4 Quantitative descriptive analysis (QDA) 68

4.2.4 Statistical analysis of data 68

4.2.4.1 Principal component analysis (PCA) 69


4.3.1 Desirable parameters of idli 70

4.3.1.1 Color 70

4.3.1.2 Fluffiness and sponginess of idli 71

4.3.1.3 Fermented aroma 74

4.3.2 Negative drivers of liking 74

4.3.2.1 Stickiness of the idli 78

4.3.2.2 Sourness of idli 78

4.3.3 Overall quality of the idli 80

4.3.4 Simultaneous optimization 80

4.3.5 Principal component analysis (PCA) 81

4.3.6 Optimization of texture and sensory attributes 82

4.4 Conclusion 83

5

Nutritional composition of optimized idli

84

5.1 Introduction 84


5.2.1 Nutritional composition of the idli 84

5.2.2 Determination of fatty acids and alcohols 84

5.2.3 Determination of oligosaccharides 85


5.3.1 Nutritional composition of idli 85

5.3.2 Fatty acids and alcohols in optimized idli 87

5.4.3 Disaccharides and oligosaccharides in optimized idli 92

5.4 Conclusion 97

6

Improving the shelf-life of ready to cook idli batter

98

6.1 Introduction 98


6.2.1 Materials 98

6.2.2 Methods 99

6.2.2.1 Preparation of batter 99

6.2.2.2 Selection of packaging materials 99

6.2.2.3 Experiment I 102

6.2.2.4 Experiment II 102

6.2.2.5 Experiment III 103


6.3.1 Respiration dynamics 104

6.3.2 Experiment I 105

6.3.3 Experiment II 111

6.3.4 Experiment III 128

6.4 Conclusion 131

Executive summary and conclusion 132

Practical implications / recommendations 135

References

Annexures

List of publications

LIST OF PLATES

2.1 City map of Puducherry showing selected areas for the study 23

3.1 Color flex 41

3.2 Cutting idli with the designed mould 43

3.3 One inch cubic mould and SMS/75mm compression probe 44

3.4 Texture analyzer 44

6.1 Modified atmosphere packaging machine 100

6.2 Respirometer connected to gas analyzer 101

LIST OF TABLES

2.1 Age and sex wise distribution of the selected respondents (N=300) 25

2.2 Educational and economic status of the selected respondents (N=300) 27

2.3 Details on breakfast consumption (N=300) 28

2.4 Idli preparation at household level (N=300) 29

2.5

Fermentation time and measures followed to control fermentation of idli

batter at households (N=300)

33

2.6 Details about purchase of commercial idli batter (N=300) 34

3.1

Central composite rotatable design: coded and actual values of independent

variables

40

3.2 Effect of rice varieties on the batter volume after fermentation 47

3.3 Effect of black gram (var. Adt 3) on the batter volume after fermentation 48

3.4

Idli batter volume characteristics as affected by parboiled rice and black

gram dhal (without husk)

48

3.5

Experimental design: CCRD with actual levels of independent variables for

color parameters

51

3.6

Experimental design: CCRD with coded and actual levels of independent

variables for TPA

56

3.7 Regression co-efficient for dependent TPA parameters 62

3.8 Analysis of variance (ANOVA) for dependent TPA parameters: f values 62

3.9 Simultaneous optimization of process parameters by desirability approach 64

4.1 Sensory attributes used for sensory analysis of idli 69

4.2 Experimental designs and mean scores of desirable sensory attributes 71

4.3 Experimental designs and mean scores of undesirable sensory attributes 75

4.4 Regression co-efficient for sensory parameters 79

4.5 Regression co-efficient for overall quality of idli 79

4.6 Simultaneous optimization of process parameters by desirability approach 81

4.7 Combined analysis of texture and sensory attributes 83

5.1 Proximate composition of optimized idli 86

5.2 List of fatty acids and alcohols 87

5.3 List of disaccharides and oligosaccharides 93

6.1 Thickness of packaging materials map of idli batter 99

6.2 Gas treatment used in experiment II 103

6.3 Gas treatment used in experiment III 103

6.4 Change in gas mixture over storage period 106

6.5 Concentration of gases in LDPE (0.014mm) during the storage period 112


2 LIST OF FIGURES

2.1 Socio-economic profile of the selected respondents 26

2.2 Details on idli preparation at household level 31

2.3 Details on fermentation time and measures to fermentation 32

3.1 Flowchart showing work design for TPA of idli 42

3.2a A. Effect of rice varieties on batter volume after fermentation 49

3.2b B. Effect of type of black gram dhal on batter volume after fermentation 49

3.2c

C. Effect of ratios of rice to black gram dhal on batter volume after

fermentation

49

3.3a

Response surface graph showing relation between independent parameters

on L*

52

3.3b


on a*

52

3.3c


on b*

53

3.3d


on chroma

53

3.4a

Fig.3.3.a texture profile of idli made of ratio 3:1.25 at 12 h fermentation

time

55

3.4b Fig.3.3.b texture profile of idli made of ratio 3:2 at 12 h fermentation time 55

3.5a

Fig.3.3.a response surface graph showing relation between independent

parameters on hardness

58

3.5b


on adhesiveness

58

3.5c


on springiness

59

3.5d


on cohesiveness

59

3.5e


on chewiness

60

3.5f Response surface graph showing relation between independent parameters 61


6.8

Sensory scores of the product made from batter packaged in LDPE

(0.014mm)

125

6.9 Sensory scores of the product made from batter packed in LDPE (0.012mm) 125

6.10


(0.009mm)

126

6.11 Comparison of gas mixture on the first day and seventh day of storage 129

6.12 TPA parameters of idli made from map batter 129

6.13 Overall quality of idli 130

on resilience

4.1a Response surface graph for color 72

4.1b Response surface graph for fluffiness 72

4.1c Response surface graph for sponginess 73

4.1d Response surface graph for fermented aroma 73

4.2a Response surface graph for compactness 76

4.2b Response surface graph for firmness 76

4.2c Response surface graph for stickiness 77

4.2d Response surface graph for sourness 77

4.3 Response surface graph showing the overall quality of the idli 80

4.4

Principal component analysis (PCA) biplot of experimental design points

over sensory attributes of idli

82

5.1

Typical chromatogram and mass spectra showing fatty acids in non-

fermented batter

88

5.2

Typical chromatogram and mass spectra showing fatty acids and alcohols in

fermented batter

89

5.3

Typical chromatogram and mass spectra showing fatty acids in optimized

idli

90

5.4

Typical chromatogram and mass spectra showing disaccharides and

oligosaccharides in non-fermented batter

94

5.5


oligosaccharides in fermented batter

95

5.6


oligosaccharides in optimized idli

96

6.1 Change in gas concentration during its fermentation time 104

6.2a

Treatment 1 (0% CO2) showing change in CO2 level (%) among different

packaging material

108

6.2b

Treatment 1 (0% CO2) showing change in O2 level (%) among different

packaging material

108

6.3a


packaging material

109

6.3b


packaging material

109

6.4a


packaging material

110

6.4b


packaging material

110

6.5a Treatment 1 (0% CO2 and 15% O2) showing percentage of CO2 (%) 115

6.5b Treatment 1 (0% CO2 and 15% O2) showing percentage of O2 (%) 115






6.8b Treatment 4 (15% CO2 and 15% o2) showing percentage of O2 (%) 118

6.9a Treatment 5 (0% CO2 and 17.5% O2) showing percentage of CO2 (%) 119

6.9b Treatment 5 (0% CO2 and 17.5% O2) showing percentage of O2 (%) 119

6.10a Treatment 8 (15% CO2 and 17.5% O2) showing percentage of CO2 (%) 120

6.10b Treatment 8 (15% CO2 and 17.5% O2) showing percentage of O2 (%) 120









6.15

Comparison of sensory scores of idli made from treatment 1 (0% CO2 and

15% O2)

127

6.16

Comparison of sensory scores of idli made from treatment 6 (5% CO2 and

15% O2)

128

0

INTRODUCTION AND

REVIEW OF LITERATURE

1

MODIFIED ATMOSPHERE PACKAGING OF READY TO COOK

IDLI BATTER

1.1 INTRODUCTION

Fermented cereals, pulses and meat are consumed throughout the world both as means of

preservation by identifying their texture, aroma and flavour in addition to their health

benefits. Idli, one of the most common traditional cereal-pulse based fermented breakfast

product is consumed mostly in the southern part of India and Sri Lanka. Idli is the most

preferred breakfast product due to its soft texture, mild pleasant flavour and aroma, easy

digestibility and known health and nutritional benefits. Even with rapid social transition,

idli still remains to be the choice of breakfast for the population either at home or home-

away. With rapid urbanization, idli is one of the most served products in the restaurants

and catering establishments. Idli being a lactic acid bacteria fermented product, is

traditionally prepared by rice and dhal soaked, ground and fermented before steamed and

consumed. With rapid urbanization, Ready to cook, packaged fermented batter is made

available in the cities by household vendors, frequently with quality and safety problems.

In spite of heavy demand there has not been proper commercialization of the product due

to lack of set quality parameters as well as issues with the shelf life of the product. There

has also been an effort made to develop starter cultures aimed at preparing the final

product with consistent sensory parameters. However these starter cultures did not

become popular due to their inferior sensory characteristics. Efforts are being made by

various research groups to develop appropriate and acceptable starter cultures for idli.

In spite of heavy demands organized food industries have not taken up the

commercialization of ready to cook idli batter in view of short shelf life. Even the

commercial prospects of scientifically developed starter cultures will remain curtailed till

the shelf life of ready to cook batter is considerably extended.

In the pursuit of extension of shelf life of ready to cook idli batter, a microbiologically

dynamic fermentation medium with other several factors needs to be kept in mind. The

product should be close to the natural as any change in the dynamics of the fermentation

flora could lead to unacceptable product characteristics. Although only a few fermented

2

products or preserved with Modified Atmosphere Packaging (MAP), most of them are

packaged after the fermentation/maturation process.

In this work an effort has been made to scientifically optimize the process of preparation

of ready to cook idli batter and packaging the ground product in the initial stages of

fermentation with optimized gas combinations supporting slow but desirable

fermentation process extending the product shelf life without affecting texture and

sensory characteristics.

1.2 REVIEW OF LITERATURE

The review of literature of the current study is done under the following headings:

1.2.1. Significance of fermented foods

1.2.2. Positive health outcomes of breakfast consumption

1.2.3. Idli and its properties

1.2.4. Rice - A staple food grain in idli making

1.2.5. Black gram - A protein source in idli making

1.2.6. Oligosaccharides in foods

1.2.6. Shelf life of fermented foods

1.2.1. SIGNIFICANCE OF FERMENTED FOODS

Fermented foods are those foods which have been subjected to the action of

microorganisms or their enzymes to produce desirable biochemical changes and results in

significant modification to the food. Fermented foods provide variety to the diet

supplying nutrients predominantly proteins and amino acids. The process of fermentation

also aids in detoxification (Campbell-Platt, 1994). Fermentation plays diverse roles like

enhancing the diet with wide range of flavours, aromas and textures, preserving

substantial amounts of food through lactic acid, alcoholic, acetic acid, alkaline

fermentations, enriching food substrates with nutrients and also reducing cooking times

3

and fuel requirements (Steinkraus, 1994). Lactic acid fermented foods are common in

tropical countries and these foods give improved organoleptic qualities (Cookey et al.,

1987).

Fermentation affords a natural way to reduce the volume of the material to be

transported, abolish undesirable components, enhance the nutritive value and improve

appearance of the food, decrease the energy required for cooking and make a safer

product (Simango, 1997). Fermented foods are produced worldwide by various

manufacturing techniques, raw materials and microorganisms. However, there are only

four main fermentation processes which include alcoholic, lactic acid, acetic acid and

alkali fermentation (Soni and Sandhu, 1989). Alcohol fermentation results in the

production of ethanol, and yeasts are the predominant organisms (e.g. wines and beer),

fermented milks and cereals are mainly conceded out by lactic acid bacteria. A second

group of bacteria significant in food fermentation is the acetic acid producers

(Acetobacter species). Acetobacter sp. converts alcohol to acetic acid in the presence of

excess oxygen (McKay and Baldwin, 1990). Likewise, fermentation significantly

improves the protein quality as well as the level of amino acid particularly lysine in

maize, millet, sorghum, and other cereals (Hamad and Fields, 1979). Fermentation also

leads to improvement in the shelf life, texture, taste and aroma of the final product.

During cereal fermentation a number of volatile compounds are formed, which contribute

to a composite blend of flavours in the products (Chavan and Kadam, 1989).

The presence of aromas representative of acetic acid and butyric acid make fermented

cereal based products more appetizing. Traditional fermented foods prepared from most

common types of cereals (such as rice, wheat, corn or sorghum) are well known in

various parts of the world. Some are utilized as colorants, spices, beverages and breakfast

or light meal foods, while a few of them are used as key foods in the diet. The

microbiology of many of these fermented products is quite complex and not known. In

most of these products, fermentation is natural and involves mixed cultures of yeasts,

bacteria and fungi. Some microorganisms may participate in parallel, while others act in a

sequential manner with exchanging dominant flora during the course of the fermentation.

The common bacteria involved in fermentation are species of Leuconostoc,

4

Lactobacillus, Streptococcus, Pediococcus, Micrococcus and Bacillus. The fungi genera

Aspergillus, Paecilomyces, Cladosporium, Fusarium and Saccharomyces (yeast) are most

often found in certain products (Blandino et al, 2003).

1.2.2. POSITIVE HEALTH OUTCOMES OF BREAKFAST CONSUMPTION

Studies done by Agostoni, et al., (2010) disclose that breakfast represents a healthy habit

and association with positive health outcomes proves breakfast should be consistent with

local and family dietary behaviours. Policies and interventions supportive of breakfast

consumption are therefore encouraged. According to neurobehavioral data, the good

example of parents and access to a variety of palatable and pleasant breakfast foods

should drive children to choose self select breakfast models with balanced composition,

while respecting recommended dietary allowances. A balanced macronutrient

composition, the proposition of a variety of models leading to a total energy density

preferably within lower ranges (< 1 to 1.5), as well as glycemic indices in the lower range

for the same food class, could emphasize the positive short and long term health

outcomes which is now attributable to breakfast.

Regular breakfast consumption can have a multitude of positive health benefits, yet

young people are more likely to skip breakfast than any other meal. Given the evidence

that dietary behaviours established in childhood and adolescence track into adulthood

along with evidence that breakfast skipping increases with age, identifying correlates of

children's and adolescent's breakfast behaviour is imperative. Few studies have examined

the same specific family correlates of breakfast consumption, limiting the possibilities of

drawing strong or consistent conclusions. Parental breakfast eating and living in two-

parent families were the correlates supported by the greatest amount of evidence in

association with adolescent's breakfast consumption. The results suggest that parents

should be encouraged to be positive role models to their children by targeting their own

dietary behaviours and that family structure should be considered when designing

programmers to promote healthy breakfast behaviours (Pearson et al., 2009).

Eating breakfast is important for the health and development of children and adolescents.

Reports on the findings of an Australian survey of 699 thirteen year old concerning the

5

extent of skipping breakfasts, indicated approximately 12 percent of the sample skipped

breakfast. Gender was the only statistically significant socio demographic variable, with

females skipping at over three times the rate of males. Skippers were more likely to be

dissatisfied with their body shape and to have been on a diet to lose weight than were

those who ate breakfast (Shaw, 1998).

Wesnes et al., (2003) reported in their study that a typical breakfast of cereal rich in

complex carbohydrates can help maintain mental performance over the morning.

Frequency of breakfast and cereal consumption decreased with age. Days eating breakfast

were associated with higher calcium and fiber intake in all models, regardless of

adjustment variable. After adjusting for energy intake, cereal consumption was related to

increased intake of fiber, calcium, iron, folic acid, vitamin C, zinc, and decreased intake

of fat and cholesterol. Cereal consumption as part of an overall healthful lifestyle may

play a role in maintaining a healthful Body Mass Index (BMI) and adequate nutrient

intake among adolescent girls (Barton et al., 2005).

1.2.3. IDLI AND ITS PROPERTIES

1.2.3.1. Nutritional composition of idli

Idli, a very popular fermented breakfast food consumed in the Indian subcontinent,

consists mainly of rice and black gram. Idli fermentation was carried out in the

conventional way in a batter having rice to black gram in the ratios of 2:1, 3:1 and 4:1 at

room temperature. It makes an important contribution to the diet as a source of protein,

calories and vitamins, especially B-complex vitamins, compared to the raw unfermented

ingredients. It can be produced locally and used as a dietary supplement in developing

countries to treat people suffering from protein calorie malnutrition and kwashiorkor

(Nagaraju and Manohar, 2000).

Adding Saccharomyces cerevisiae, along with natural bacterial flora of the ingredients,

was the best method for standardizing idli fermentation in terms of improved

organoleptic characteristics, leavening and nutritional constituents. Traditional idli

fermentation involves several bacteria and yeasts, contributed by the ingredients rice

(Oryza sativa), black gram (Phaseolus mungo) and the environment, with overall

6

dominance of the former in bringing about various changes. Idli fermentation is

accompanied by an increase in total acids, batter volume, soluble solids, reducing sugars,

non protein nitrogen, free amino acids, amylases, proteinases and water soluble vitamins

B1, B2 and B12 contents, thus accounting for improved digestibility and nutritional value

of the staples. Novel idli batter prepared by replacing conventional black gram with other

legumes, revealed significant change but with difference in the levels of some

biochemical constituents (Soni and Sandhu, 1989).

Idli, Dhokla, Nan, Kulcha, Bread, Jalebi, Bhatura, Bhalla, Dosa, Gulgule and Wadian

were prepared in the laboratory using traditional fermentation techniques. The fermented

batter of idli and dosa contained higher amount of available lysine, cystine and

methionine. After processing, maximum retention of lysine, methionine and cystine was

observed in steamed idli (Riat and Sadana, 2009).

Growth and nitrogen balance feeding trials were conducted with rats to determine the

protein quality of idli, a fermented steamed cake prepared from beans (Phaseolus

vulgaris) and rice. Feed Efficiency Ratio (FER), Protein Efficiency Ratio (PER) and

Relative PER (RPER) of fermented idli diets were significantly lower (p<0.05) than the

FER, PER and PER of unfermented idli diets. The Digestibility Coefficient (DC) and Net

Protein Utilization (NPU) of fermented idli diets were significantly lower (p<0.05) than

the DC and NPU of unfermented idli diets. Biological Value (BV) of fermented and

unfermented idli diets was similar to the BV of a caesin control diet. Fermentation does

not improve the protein quality of idli prepared from beans and rice (Joseph and

Swanson, 1994).

1.2.3.2. Physico chemical parameters of idli

Balasubramanian and Viswanathan (2007a) has shown that idli batter was prepared from

soaking polished parboiled rice and decorticated black gram. The blend a ratio of 2:1, 3:1

and 4:1 (v/v) and the batter was allowed for fermentation (0, 6, 12, 18 and 24 h) adding

two percent of salt. Other legumes such as soybeans and Great Northern beans could be

substituted for black gram in preparation of idli (Reddy et al., 1981). Fermentation time

of the batter varies from 14 to 24 h with overnight fermentation being the most frequent

7

time interval. The ingredients for idli are carefully washed, soaked in water separately,

grounded, mixed, and finally allowed to ferment overnight. When the batter has been

raised sufficiently, it is cooked by steaming and served hot. The product has a very soft

and spongy texture and a desirably sour flavour and taste. The black gram was washed

several times, first with tap water and finally with distilled water to remove the surface

microorganisms. These were found to produce off flavour in the idli unless they were

washed out (Mukherjee et al., 1965).

Mukherjee et al., (1965), studied the fermentation of idli batter. The microorganisms

responsible for the characteristic changes in the batter were isolated and identified.

Although there is a sequential change in the bacterial flora, the predominant

microorganism responsible for souring, as well as for gas production, was found to be

Leuconostoc mesenteroides. In the later stages of fermentation, growth of Streptococcus

faecalis and, followed by Pediococcus cerevisiae became significant. The fermentation of

idli demonstrates a leavening action caused by the activity of the hetero fermentative

lactic acid bacterium, L. mesenteroides. As far as is known, this is the first record of a

leavening action produced exclusively by the activity of a lactic acid bacterium.

Idli is traditional fermented rice and black gram based breakfast food of South India. Idli

batter was prepared from soaking polished parboiled rice and decorticated black gram for

4 h at 30 ± 1oC in water. The soaked mass was ground to 0.5 to 0.7 mm particle size

batter using wet grinder with adequate amount of water. The idli batter parameters such

as bulk density, pH, total acidity, flow behaviour index and consistency coefficients were

studied for different fermentation times and blend ratios. The bulk density, pH and

percentage total acidity of batter during different fermentation times and blend ratios

ranged between 0.94 and 0.59 g/cm3, 5.9 and 4.1 and 0.443 and 0.910%, respectively.

The consistency coefficient at any fermentation time shows increasing trend as the rice to

black gram ratio increased. The flow behaviour index indicated strong non-Newtonian

fluid behaviour (pseudoplastic) of idli batter at different fermentation times and blend

ratios (Balasubramanian and Viswanathan 2007a).

The rheology of the idli batter was assessed using a Brookfield viscometer having disc

spindles. Power law model with yield stress adequately fitted the data. Yield stress values

8

were in the range of 13-43 Pa and reached a maximum value at 7 h of fermentation. Flow

behaviour indices were in the range of 0.287-0.605. Flow behaviour indices at 23 h were

significantly lower than those at 0 h. Consistency index values, at any fermentation time,

increased as the rice to black gram ratio increased. Mean particle size ranged from 500 to

600 micro meter and there was no definite trend noticed with respect to time of

fermentation and rice to black gram ratio. There was a steep change in volume increase

after 4-h fermentation (Nagaraju and Manohar, 2000).

The idli batter comprises lactic acid bacteria and yeasts and causes an improvement in the

nutritional, textural and flavour characteristics of the final product. The desirable flavour

compounds such as ketones, diols and acids were found to be present up to eight days of

storage, whereas undesirable flavours like sulphurous and oxazolidone compounds,

ethanone and thiazole appeared in the batter subsequent to six days of storage. The

sensory attributes of idli (final product) prepared from the stored batter related well to the

determined flavour profile (Agrawal et al., 2000).

The work done by Nisha et al., (2005) stabilized the idli batter at room temperature (28-

30°C) and refrigerated storage (4-8°C) by using various hydrocolloids and some surface-

active agents. The batter was evaluated in terms of decrease in volume, and whey

separation. While hydrocolloids gave good stabilization, surface-active agents failed to

stabilize the batter and they reduced whey separation. Among the various hydrocolloids,

0.1percent guar gave best batter stabilization, and idli made after ten days of room

temperature and 30 days of refrigerated storage of batter were found to be of acceptable

quality.

Reduction in the fermentation time of the idli batter is of great commercial significance

for large-scale idli production and can be potentially achieved by addition of enzymes.

The study done by Iyer and Anathanarayan, (2008) was undertaken to explore the

possibility of expediting the idli batter fermentation process by adding an exogenous

source of α-amylase enzyme. 5, 15 and 25 U per 100 g batter of amylase added to the idli

batter was allowed to ferment. Different parameters were monitored and sensory

attributes were also studied and compared with that of the control set. The fermentation

9

time was reduced from a conventional 14 h to 8 h and the sensory attributes of the final

product were also successfully maintained.

Texture Profile Analysis (TPA) test was performed for idli, making cylinder samples

(13.5 mm diameter, 10 mm long) of idli. In Pearson correlation matrix, majority of the

parameters were positively correlated at p<0.01 and p<0.05. The firmness value

positively correlated with gumminess and chewiness, which depicts the soft nature of idli

(Balasubramanian and Viswanathan 2007b).

1.2.4. RICE - A STAPLE FOOD GRAIN IN IDLI MAKING

Cereal grains particularly rice, form a major source of dietary nutrients for all people,

particularly those in the developing countries. However, compared with animal foods,

nutritional quality of cereal grains is inferior due to lower protein content, deficiency of

certain essential amino acids, lower protein and starch availabilities, and the presence of

some antinutritional factors. Fermentation of cereals for a limited period of time

improves amino acid composition and vitamin content, increases protein and starch

availabilities, and lowers the levels of antinutrients. The traditional foods prepared by

fermentation of cereals in different parts of the world are briefly described and future

research needs to improve their nutritional contribution are addressed (Chavan et al.,

1989).

Cereals are deficient in lysine, but are rich in cysteine and methionine. Legumes, on the

other hand, are rich in lysine but deficient in sulphur containing amino acids. Thus, by

combining cereal with legumes, the overall protein quality is improved (Camphell-Platt,

1994). Fermented foods prepared from cereals and legumes are an important part of the

human diet in Southeast Asia and parts of East Africa. The popularity of legume based

fermented foods is due to desirable changes including texture and organoleptic

characteristics. Improvement in digestibility and enhancement of keeping quality, partial

or complete elimination of anti-nutritional factors or natural toxins, increased nutritive

value, and reduced cooking time (Joseph, 1994).

Cereal grains constitute a major source of dietary nutrients all over the world. Although

cereals are deficient in some basic components, fermentation may be the most simple and

10

economical way of improving their nutritional value, sensory properties, and functional

qualities. Products produced from different cereal substrates (sometimes mixed with

other pulses) fermented by lactic acid bacteria, yeast and/or fungi (Blandino et al., 2003).

Rice colour changes from white to amber during parboiling (soaking and steaming).

Colour parameters indicated that, during soaking, yellow bran pigments leaches out in the

water. The levels of the Maillard precursors (i.e., reducing sugars and free α-amino

nitrogen (FAN)) depends on soaking temperature and time: leaching of RS was

compensated by enzymatic formation for long soaking times (>60 min), while proteolytic

activity was too low to compensate for FAN leaching. Parboiled rice soaking under

nitrogen, oxygen, or ambient conditions and determination of polyphenol oxidase activity

allowed to conclude that the effect of enzymatic colour changes on the soaked rice colour

was rather small. Colour measurements of brown and milled mildly, intermediately, and

severely parboiled rice samples showed that both brown and milled rice samples were

darker and more red and yellow after parboiling and that the effect depended on the

severity of parboiling conditions. Furthermore, steaming affected the rice colour more

and in a way opposite to that observed in soaking (Lamberts et al., 2006).

Parboiled brown rice contained considerably more Reducing Sugars (RS) but less sucrose

and Free Amino Acids (FAA) than raw brown rice. On milling, there was considerable

loss of sucrose and FAA from raw rice, but very little from parboiled rice; reducing

sugars changed little in either. Processing conditions affected the contents of sugars and

FAA. Maximum increase in RS and decrease in sucrose content occurred after soaking at

60C. Controlled incubation of rice flour, intact grain, separated germ and deemed rice in

water showed that considerable changes in sugars and FAA occurred in all cases, the

magnitude depending on the circumstances, but a greater part of the sugars leached out

into the water during soaking (Ali and Bhattacharya, 1980).

Grinding characteristics of raw and parboiled rice were evaluated in various wet grinding

systems like, mixer grinder, stone grinder and colloid mill. The duration of grinding had

inverse effect on the particle size and direct impact on the starch damage as well as

energy consumption in batch grinders. Stone grinder was the least energy efficient and

specific energy consumption for grinding raw rice (160.6 kJ/kg) was nearly twice as that

11

of mixer grinder (74.9 kJ/kg). Parboiled rice required longer duration of grinding

compared to raw rice, consequently specific energy consumption was higher (∼220

kJ/kg) (Sharma et al., 2008). Wet grinding is a critical step in the preparation of batter

based traditional food products. It involves both physical and chemical changes while dry

grinding is a mere size reduction operation. In wet grinding of cereals, the protein matrix

holding the starch granules is destroyed, releasing the starch granules from the protein

network (Kent and Evers, 1994). A colloid mil was comparatively evaluated with

domestic wet grinding systems, namely, a mixer grinder and a stone grinder for grinding

of raw rice, parboiled rice and black gram. The wet ground samples were finer in particle

size compared with dry ground samples. The starch damage was the least in black gram

followed by raw rice and parboiled rice in dry grinding. In wet grinding, the starch

damage in black gram as well as raw rice remained more or less same whereas the

parboiled rice showed greater damage. Parboiled rice required 2.5 to 3 times more energy

(216-252 kJ/kg) as that of raw rice (72-108 kJ/kg) for grinding in the mixer grinder and

the stone grinder (Solanki et al., 2005)

The nutritional quality of wild rice tends to be comparable with other cereals

characterized by a high content of starch and protein and a low fat content. As a whole

grain, wild rice is also a good source of dietary fibre (Qiu et al., 2010).The presence of

Streptococcus faecalis in the fermented batter, the presence of pharmacological active

amines such as thiamine was expected but they were not detected (VanVeen, et al.,

2008).

Parboiled brown rice contained considerably more (RS) but less sucrose and FAA than

raw brown rice. On milling, there was considerably loss of sucrose and FAA from raw

rice, but very little from parboiled rice; reducing sugars and FAA. Maximum increase in

RS and decrease in sucrose content occurred after soaking at 600

C (Ali et al., 2007).

Larsen et al., (2000) opines that rice is an important crop, forming a staple food for many

of the world‘s population. A study showed there was an effect of severely pressure

parboiled rice reduced the glycaemic index.

Brown rice malt from Indica and Japonica type rice were prepared and their nutrient

composition as well as Non-Starch Polysaccharide (NSP) contents and also some of the

12

physicochemical characteristics were determined. The activity of α- and β-amylases in

the un-germinated (native) rice was negligible but increased considerably on germination.

Malting altered the chemical composition of both Indica and Japonica rice to a small

extent but caused noticeable changes in the pasting characteristics. Controlled

germination or malting causes considerable changes in the physicochemical and

biochemical properties of both Indica and Japonica rice (Mohan et al., 2010). Whole

grain rice is rich in phenolic compounds. The effect of γ-irradiation on the main phenolic

compounds in the rice grains of three genotypes (black, red, and white) was investigated.

Three phenolic acids (p-coumaric acid, ferulic acid, and sinapinic acid) were identified as

major phenolic compounds in all rice samples, while two anthocyanins (cyanidin-3-

glucoside and peonidin-3-glucoside) were identified in pigmented grain samples (Zhu et

al., 2010).

1.2.5. BLACK GRAM A PROTEIN SOURCE IN IDLI MAKING

Blackgram (Phaseolus mungo) is a pulse traditionally used in the preparation of

South Indian breakfast foods, such as idli, which is relished for its soft and spongy

texture (Susheelamma and Rao, 1979a). The components responsible for these

properties are the surface active proteins that generate a foam and as a result

impart a porous structure to the food, and the viscogenic mucilaginous

polysaccharide (~6%) that stabilizes the porous structure against thermal disruption

during steaming. The overall carbohydrate composition (Bhat and Tharanathan,

1986) and the structure function characteristics of the total polysaccharides of black

gram have been reported. During fermentation of black gram, for the preparation of

leavened foods, it was found that the mucilaginous polysaccharide undergoes

compositional and rheological changes (Muralikrishna et al.,1987). Here, the

fermentation is due to the activities of endogenous microflora (endophytes) in black

gram, in particular Leuconostoc mesenteroides, yeasts, lactic acid bacteria and

coliforms. More than one oligosaccharide was observed as in green gram (stachyose,

maltohexaose), sorghum (stachyose, maltotriose), barley (stachyose, raffinose), wheat

(stachyose, raffinose) and black gram (stachyose, raffinose). In ragi, bajra and rice malt

oligosaccharides were absent. Germination of seeds for 48 h resulted in complete loss of

13

stachyose and raffinose in cereals and pulses. The maltotriose content in pulses

completely disappeared on germination but among cereals, 45.1 and 57.3 percent loss

was observed in sorghum and maize, respectively (Sampath et al., 2008). In black gram

after fermentation, apparent viscosity of cold paste increased. Some of the properties such

as intrinsic viscosity, swelling and solubility after fermentation were reported by them.

Fermentation and steaming approximately 40 per cent reduction in oligosaccharides

resulting in reduced flatulence in the body (Koh and Singh, 2009).

Nutritional benefits are produced in legume fermentations, when microorganisms break

down the flatulence causing indigestible oligosaccharides, such as stachyose and

verbascose are broken down into the absorbable monosaccharaides and disaccharides.

Biosynthesis of B vitamins in food fermentations has been recognized to be of major

nutritional significance, particularly in Africa where high-carbohydrate diets, particularly

maize diets can be deficient in essential B vitamins, the significance of B vitamin

synthesis during fermentation to maize and sorghum beers in southern Africa was

recognized by the use of the term ‗biological ennoblement‘ by Platt (1964).

1.2.6. OLIGOSACCHARIDES IN FOODS

Carbohydrates are classified into monosaccharide, disaccharides, oligosaccharides and

polysaccharides. Oligosaccharides are low molecular weight carbohydrates consisting 3

to 10 sugar monomers (Voragen, 1998). Oligosaccharides withstand salivary hydrolysis

and digestive enzymes of human animal intestine so these oligosaccharides are not

absorbed in the upper digestive tract and are able to reach the colon unaltered. In colon,

oligosaccharides interact with the microflora and affecting immunomodulation (Reiffova

and Nemcova, 2006). The non-digestible oligosaccharides promote the growth of

beneficial bacteria in the colon, chiefly the Bifidobacteria sp., and are thus recognized as

prebiotics (Mussatto and Mancilha, 2006). Most of the known prebiotics and prebiotic

candidates are nondigestible oligosaccharides, obtained by extraction from plants (e.g.,

chicory inulin), followed by enzymatic hydrolysis (e.g., oligofructose from inulin) and by

synthesis (by trans-glycosylation reactions) from mono and/or disaccharides such as

sucrose (fructooligosaccharides) and lactose (trans-galactosylated

oligosaccharides/galactooligosaccharides) (Crittenden and Playne, 1996). Among the

14

prebiotics, inulin and oligosaccharides are the most studied and have been recognized as

dietary fibre worldwide (Moshfegh et al., 1999).

1.2.6.1Conversion of polysaccharides into oligosaccharides

Polysaccharides are the major source of bioactive oligosaccharides and around twenty

different types of non-digestible oligosaccharides (NDOs) are described for prebiotic

activities. Fructooligosaccharides, galacto-oligosaccharides, xylo-oligosaccharides and

galacturono-oligosaccharides are predominant NDOs with prebiotic characteristics.

Oligosaccharides are recognized as non-cariogenic, non-digestible and low-calorie

molecules and can be used as natural food preservatives. Chitosan and oligochitosans,

inhibits growth of pathogens and extends shelf-life of food products (Barreteau et al.,

2006).

Glycosyl-hydrolases and polysaccharide lyases, are used to obtain oligosaccharide from

polysaccharides. Polysaccharide chains were broken down by polysaccharide lyases and

form a double bond at new reducing end (Michaud et al., 2003). Polysaccharide

hydrolase cleave glycosidic bond by transfer of a H2O molecule and act as

exohydrolases/endohydrolases (Boels et al., 2001; Bojarova and Kren, 2007). Enzyme

used for the purpose must be specific to the substrate should be more efficient. The

solution for having enzyme specificity is to use bacteria to produce particular enzyme.

From the bacteria the specific enzyme of the polysaccharide can be isolated, purified and

concentrated and used (Sutherland, 1999).

1.2.6.2. Physiological properties of oligosaccharides

Oligosaccharides possess important physicochemical properties. They are used as food

ingredients as their physiological properties were beneficial to human health. The NDOs

can be used as low caricinogenic sugar surrogates in products like confectionery,

chewing gums, yoghurts and drinks (Crittenden and Playne, 1996). Many NDOs are not

digested by humans because the human body doesn‘t have the enzymes necessary to

hydrolyze certain units of monosaccharides. Compounds include carbohydrates where

fructose, galactose, glucose and/or xylose are the monosaccharides units. This property of

NDOs makes the suitable for use in sweet, low-caloric diet foods, and for consumption

15

by individuals with diabetes (Crittenden and Playne, 1996; Rivero-Urgell and

Santamaria-Orleans, 2001).

Most oligosaccharides were quantitatively hydrolyzed in the upper part of the GIT. The

resulting monosaccharides are transported through the portal blood to the liver and

subsequently, to the circulatory system. These carbohydrates are important for health as

they serve as both substrates and regulators for major metabolic pathways. Nevertheless,

some oligosaccharides present specific physicochemical properties resist to the digestive

process, reaching the caeco colon. In the caeco-colon, most of the nondigestible

oligosaccharides were hydrolyzed to small oligomers and monomers and further

metabolized by most of the anaerobic bacteria. Such a metabolic process, known as

fermentation, not only serves the bacteria by providing energy for proliferation, but it

also produces gases (H2, CO2, CH4), which are metabolically useless to the host, and

small organic acids (Short-Chain Fatty Acids – SCFA) such as acetate, propionate,

butyrate and L-lactate. Even though they do not provide the body with monosaccharaides,

the non-digestible oligosaccharides are indirect energy substrates and metabolic

regulators (Delzenne and Roberfroid, 1994). The amounts and types of SCFA produced

in the colon depend on the type of NDO substrate as well as on the composition of the

intestinal flora (Sako et al., 1999).

Oligosaccharides serve as substrate for growth and proliferation of anaerobic bacteria,

mainly the Bifidobacteria, which inhibit the growth of putrefactive and pathogenic

bacteria present in the caeco-colon (Sangeetha et al., 2005).

NDOs leads to decrease of pH in the colon and consequently, in faeces, resulting from

the production of SCFA. Lower pH values inhibit the growth of certain pathogenic

bacteria species while stimulating the growth of the bifidobacteria and other lactic acid

species (Manning and Gibson, 2004). An increase in faecal dry weight excretion, which

is related to the increased number of bacteria resulting from the extensive fermentation of

NDOs (Bielecka et al., 2002)

The indigestible quality of NDOs means that they have effects similar to dietary fibre,

and thus prevent constipation. The end products of NDOs fermentation by colonic

16

bacteria, the SCFA, are efficiently absorbed and utilized by the human colonic epithelial

cells, stimulating their growth as well as the salt and water absorption, increasing thus the

humidity of the fecal bolus through osmotic pressure, and consequently improving the

intestinal motility (Rivero-Urgell and Santamaria-Orleans , 2001). NDOs help in

inhibition of diarrhea, especially when it is associated with intestinal infections

(Roberfroid and Slavin, 2000).

An increase in absorption of different minerals, such as iron, calcium, and magnesium

take place due to the binding/sequestering capacity of the NDOs. The minerals that are

bound/sequestered and, consequently, are not absorbed in the small intestine reach the

colon, where they are released from the carbohydrate matrix and absorbed. The increase

on calcium absorption, in particular, reduces the risk of osteoporosis since this mineral

promotes an increase in the bone density and bone mass. The hypotheses most frequently

proposed to explain this enhancing effect of NDOs on mineral absorption are the osmotic

effect, acidification of the colonic content due to fermentation and production of SCFA,

formation of calcium and magnesium salts of these acids, hypertrophy of the colon wall

(Younes, 1996).

Beneficial effect on the carbohydrates and lipids metabolism is that oligosaccharides lead

to a decrease in the cholesterol, triglycerides and phospholipids concentration in the

blood, reducing thus the risk of diabetes and obesity. Changes in the concentration of

serum cholesterol have been related with changes in the intestinal microflora. Some

strains of Lactobacillus acidophilus assimilate the cholesterol present in the medium,

while others appear to inhibit the absorption of cholesterol through the intestinal wall. On

the other hand, the changes in lipid metabolism were suggested to be a consequence of a

metabolic adaptation of the liver that might be induced by SCFA (Daubiol et al., 2000).

NDOs aid in reduction of cancer risk, mainly the gut cancer. This anti-carcinogenic effect

appears to be related to an increase in cellular immunity, the components of the cell wall

and the extra-cellular components of bifidobacteria. Faecal physiological parameters such

as pH, ammonia, p-cresol, and indole are considered to be risk factors not only for colon

cancer development but also for systemic disorders. It has been demonstrated in a human

study that the intake of trans-galactosylated disaccharides reduces the faecal pH as well

17

as ammonia, p-cresol and indole concentrations with an increase in bifidobacteria and

lactobacilli and a decrease in bacteroid populations. These alterations may be considered

to be beneficial in reducing the risk of cancer development. A low colonic pH may also

aid in the excretion of carcinogens (Delzenne and Roberfroid ,1994)

1.2.6.3 Animal studies on Oligosaccharides

Feeding mice with diets supplemented with inulin and oligofructose increased activities

of natural killer cells and phagocytes and enhanced T-lymphocyte functions compared to

mice fed diets with cellulose or lacking fibre. These results are consistent with the

observations of heightened resistance to systemic infections with Listeria spp. and

Salmonella spp., the lower incidence and growth of tumours after exposure to

carcinogens and transplanted tumour cells and are in agreement with enhanced innate and

acquired immune functions provided by Lactobacillus and other LAB. Supplementing

diets with FOS should increase production of SCFA, and particularly butyrate, and can be

predicted to strengthen mucosal defences and enhance response to health challenges

(Buddington et al., 2002).

Colonic fermentation of FOS results in the synthesis of short chain fatty acids, which

influences the lipid metabolism in human beings. Feeding male Wistar rats on a

carbohydrate rich diet containing 10 percent FOS significantly lowers serum

triacylglycerol (TAG) and phospholipid concentration (Delzenne et al., 2002).

FOS reduces post-prandial triglyceridemia by 50% and avoids the increase in serum free

cholesterol level occurring in rats fed with a Western type high fat diet. FOS protects rats

against steatosis (liver TAG accumulation) induced by fructose, or occurring in obese

Zucker fa/fa rats. FOS given at the dose of 10 percent in the diet of male Wistar rats for

30 days reduces postprandial insulinemia by 26 percent (Daubiol et al., 2000).

Animal studies provide strong evidence that FOS inhibit secretion of TAG rich Very Low

Density Lipoprotein (VLDL) particles via inhibition of de novo fatty acid synthesis. High

levels of fat present inmost human diets mean that rates of hepatic de novo fatty acid

synthesis are extremely low, since exogenous dietary fatty acids provide all the required

substrate for hepatic triacylglycerol synthesis (Parks, 2002).

18

Dietary treatment with inulin/oligofructose (15 percent) incorporated in the basal diets for

experimental animals resulted in (a) reduction of the incidence of mammary tumours

induced in Sprague Dawley rats by methyl-nitrosourea (b) inhibited the growth of

transplantable malignant tumours in mice and (c) decreased the incidence of lung

metastases of a malignant tumour implanted intramuscularly in mice. It is reported that

the dietary treatment with FOS/inulin significantly potentiated the effects of sub-

therapeutic doses of six different cytotoxic drugs commonly utilized in human cancer

treatment (Taper and Roberfroid, 2002).

Roberfroid and Slavin, (2000) has reported that feeding rats with FOS (10 percent) for a

few weeks decreased uremia in both normal and nephrectomized rats. Dietary FOS

enhanced faecal nitrogen excretion and reduced renal excretion of nitrogen in rats. This

occurs because these fermentable carbohydrates serve as energy source for the intestinal

bacteria, which during growth also require a source of nitrogen for protein synthesis.

1.2.6.4 Applications of FOS in food formulations

Inulin and oligofructose are ingredients that deliver a number of important nutritional

benefits as well as contribute functional properties that enhance shelf life and taste profile

of various food products like nutrition bars (Izzo and Niness, 2001). FOS can be used as

the sole sweetening agent and gives 34 percent calorie reduction compared with sucrose

standard. Organoleptic characteristics of the products are claimed to be very similar, with

the test sample having a lower sweetness and a softer texture. FOS can be used with

inulin to replace all the sugar and reduce the fat content and give excellent mouth feel

characteristics. Since the freezing point depression is less with oligo-fructose than with

sugar, the texture can be harder. Hard candies, gums, and marshmallows can be made

while achieving significantly reduced energy values (Murphy, 2001).

1.2.7 MODIFIED ATMOSPHERE PACKAGING

The common perception that modified atmospheres are useful for improving storability

has significant historical precedent. The written history of the use of modified

atmospheres can actually be traced back at least 2000 years to the use of underground,

sealed silos (Owen, 1800) where atmosphere modification was detected as ―foul air‖ that

19

was dangerous to enter and was likely a result of O2 depletion and CO2 accumulation due

to the respiratory activity of the grain. The modified atmosphere was unintentional,

although probably beneficial. The foul air in the storages would presumably control

rodent and insect pests, thereby acting to preserve the quality and storage life of the grain.

The potential for a positive impact from alteration in the respiratory gases O2 and CO2

became increasingly known through the early research of Berard (1821), Mangin (1896),

Kidd and West (1914, 1927, 1945), and Blackman and Parija (1928).

Gas modification technologies can be segregated into two classes based on the manner in

which the atmospheres are generated and maintained. One class of technologies is

referred to as Controlled Atmosphere (CA) storage, in which the atmosphere is either

manually or mechanically controlled to achieve target headspace gas concentrations. In

CA storages, O2 and CO2 concentrations can be modulated independently from one

another. The second class of technologies is (MAP), in which a package possessing a film

or foil barrier passively limits gas exchange by the living produce enclosed in the

package, thereby altering the headspace atmosphere. In MAP, both oxygen and carbon

dioxide are modified simultaneously and their concentrations at steady state are a

function of one another. In MAP, the primary route of gas exchange may be through gas-

permeable film, perforations in film, or both. In what is referred to as active or intelligent

packaging techniques, packages may be flushed with specific gas mixtures designed to

obtain a desired initial atmospheric composition, gases may be actively released or

scavenged in the package, a partial vacuum can be imposed, biologically active materials

can be incorporated in the package, sensors may be used to respond to the product or

package conditions, and so on. The aim of MAP (passive, active, or intelligent in design)

is to take advantage of physiological responses of the enclosed plant material or plant or

human pathogens to the respiratory gases O2 and CO2. Presumably, MAP use is intended

to maintain product quality, thereby ensuring appropriate value to the consumer and

adequate cash flow back through the marketing and handling chain such that the

production and marketing system is sustainable .Knowledge of the physiological

responses to atmosphere modification is beneficial in terms of anticipating improved

quality retention as a result of technology investment (Beaudry, 2008).

20

Atmosphere modification in a package requires a barrier through which gas exchange is

restricted. Enclosing an actively respiring product within a package composed all or in

part of a film that acts as a gas barrier reduces O2 and increases CO2, creating gradients

across the film barrier. These gradients provide the driving force for gas flux into or out

of the package. In passive MAP, a package always tends toward steady state, in which O2

and CO2 levels are constant and O2 uptake and CO2 production by the product are equal

to those permeating through the package, a situation that exists only when the respiratory

rate is constant or nearly so. The steady-state levels of O2 and CO2 within a package are

dependent on the interaction of respiration of the product and the permeability properties

of packaging film or micro- perforations (Beaudry et al., 1992; Cameron et al., 1989;

Jurin and Karel, 1963; Kader et al., 1989).

MAP should be carefully designed, as a system incorrectly designed may be ineffective

or even shorten the shelf life of the product. The design should take into consideration not

only steady-state conditions, but also the dynamic process, because if the product is

exposed for a long time to unsuitable gas composition before reaching the adequate

atmosphere, the package may have no benefit. The design of Modified atmosphere

package depends on a number of variables, the characteristics of the product, its mass, the

recommend atmosphere composition, the permeability of the packaging materials to

gases and its dependence on temperature and the respiration rate of the product as

affected by different gas composition and temperature. Since, respiration rate modelling

is vital to the design of MAP for fresh fruits and vegetables (Fonseca et al., 2002).

Temperature is exceptionally important in package design, continuous and perforated

films differ in their response to temperature changes. The O2 and CO2 permeability of

continuous films increases with temperature, while the diffusion of gases through

perforations is extremely insensitive to temperature changes. O2 permeation over LDPE

increases 200% in 0 to 15°C, an exchange of O2 over perforations increases only 11% at

the same temperature range. Depends on the rate of respiration and transmission, the

atmosphere modification can be achieved quickly or relatively slow. At lower

temperatures, atmosphere modification will take several days, that some package systems

cannot achieve steady-state environments prior to the end of their shelf-life. In many

21

cases, purging the package atmosphere with CO2, N2 or a combination of gases is often

desirable during filling and sealing to rapidly obtain the maximum benefits of MAP.

Product temperature affects storability more than any other factor. Pre-cooling and

temperature maintenance during handling and shipping were critical in preserving

quality. Temperature also significantly affects permeability of film and thereby the O2

and CO2 content of the package. The elevated rate of respiration at high temperature

could be used to rapidly establish the desired package atmosphere, but this would only be

useful in the few circumstances in which it would be more important to rapidly establish

the atmosphere than to slow physiological processes, eg., to reduce cut-surface browning.

Negative Responses in MAP show that respiration gets reduced as O2 becomes limiting,

but there is usually a limit to which O2 can be reduced. The lower O2 limit is frequently

considered to be the level of O2 that induces fermentation. This fermentation threshold is

not always the lower O2 limit in commercial practice, however, because lower O2 levels

may confer benefits that outweigh the loss in flavour or other quality parameters.

Ethanol, acetaldehyde, ethyl acetate and lactate are products of fermentation that can

contribute to the development of off-flavours as well as physical injury (Kays, 1997;

Mattheis and Fellman, 2000).

With regard to MAP study done by Fandos et.al (2000) on Cameros cheese, it was found

that packaging in 50%CO2/50%N2 and 40%CO2/60%N2 were the most effective

conditions for extending the shelf life of cheese with good sensory characteristics. MAP

studies have been done in iced fresh hake slices (Pastoriza et al, 1996), Fresh cut

mangoes (Aguliar et al, 2000), fresh-cut ice berg lettuce (Fan et al, 2003), refrigerated

sea bass slices (Masniyom et al, 2002), blueberry (Song et al, 2002), minimally

processed mango and pineapple fruits (Martínez-Ferrer et al, 2002), pomegranate (Artes

et al, 2000).

From the review of literature and state of the art it is clear that there are no studies on

optimization of idli with respect to components and fermentation time taking into

consideration, both instrument based texture analysis and 15mm rating scale and

combination of RSM and PCA to evolve the optimized parameters for idli. In addition

there are no studies which deal with improvement of shelf life of idli batter with modified

22

atmosphere packaging. In continuation with this, the present study has been planned with

an objective to improve the shelf life of ready to cook idli batter using modified

atmosphere packaging.

The set objective is achieved through following the three major sub-objectives:

1. To understand the presently followed practices for the preparation of idli.

2. To optimize the process of preparation of the product with respect to

ingredient ratios and fermentation time.

3. To improve the shelf-life of ready to cook idli batter by optimized process.

23

TRANSITION IN THE PREPARATION AND CONSUMPTION OF IDLI

AMONG THE POPULATION OF PUDUCHERRY

2.1 INTRODUCTION

Idli occupies a special place in the diets of Indians and is one of the predominant choices

of food in the daily diet particularly as a breakfast food. Idli being a fermented food

possesses a great significance as it provides aroma and soft texture and also act as a

nutritious food. The current study was undertaken among the selected population to study

the preference of idli, consumption pattern of breakfast, preparation of idli at household

level and preference of commercial idli batter against homemade batter.

2.2 MATERIALS AND METHODS

2.2.1 Selection of area

The area selected for the study was Union Territory of Puducherry which has a

population of 12.44 lakhs (Puducherry population census, 2011) representing multi-

lingual and multi-cultural population. Eight areas namely Kalapet, Muthaiyalpet,

Villiyanur, Gorimed, Thattanchavadi, Lawspet, Vandrampet and Uppalam were selected

for the study .Plate 2.1 shows selected areas in the city map of Puducherry.

Plate 2.1 City map of Puducherry showing selected areas for the study

24

2.2.2 Selection of tool for data collection

An oral interview schedule was formulated to collect information regarding the

consumption of idli and preference of commercial idli batter. Interview schedule

(Annexure - I) included questions regarding socio-economic status, preference for idli,

preparation of idli at house hold level, consumption pattern of idli and commercial idli

batter. This formulated tool was tested on a pilot population, based upon the suggestions

the corrections were implemented and the questionnaire was used to collect information

from the respondents.

2.2.3 Selection of respondents

In total 300 respondents were randomly surveyed for the study irrespective of the cultural

and linguistic background

2.2.4 Data Analysis

The collected data were statistically treated for distributional analysis using SPSS

Statistical software (18.0).

2.3 RESULTS AND DISCUSSION

The results and discussion of the present study is discussed under the following

2.3.1 Socio-economic profile of the selected respondents

2.3.2 Consumption pattern of breakfast among the selected respondents

2.3.3 Methods of preparation of idli at household level

2.3.4 Preference for commercial idli batter against home-made batter

2.3.1 Socio-economic profile of the selected respondents

The details on the age, sex, educational qualification, employment and economic status of

the respondents are discussed. Table 2.1 shows the age (Fig. 2.1.a) and sex-wise

distribution of the selected respondents. Table 2.1 showed that, 62 per cent of the selected

respondents were in the age group of 21 to 40and only 2.66 per cent were in the age

group of 61 to70 years. Among 300 respondents, four per cent people were male and 96

per cent people were female. From this data, it is clearly noted that the study is correlated

with female respondents who are the majority home makers. Women are the integral part

of family (Jan and Akhtar, 2008) and vital force in the decision making concerning child

25

growth, money management, health and nutrition, and socio-economic progress of the

family.

Table 2.1

Age and sex wise distribution of the selected respondents (N=300)

Particulars Percentage (%)

Age (in years)

21-30 31.66

31-40 31.66

41-50 26.33

51-60 07.66

61-70 02.66

Sex

Male 03.66

Female 96.33

From Table 2.2 and Fig. 2.1.b it was noted that 82 per cent of the selected population

were literates and 18 per cent were illiterates. According to HUDCO (2004), the total

family income for low income group ranged from Rs. 2500 to Rs. 4500, for middle

income Rs. 4501 to Rs.7500 and for high income Rs. 7501 and above. In the present

study majority (50%) of the population fell under high income group, 22 per cent

belonged to middle income group and 18.3 per cent fell below low income group

(Fig.2.1.c). Hence the study covered the respondents from almost all income groups with

regard to occupational status. Of the population majority (71%) was housewives and 22

per cent were labourer earning daily wages and six per cent were only self-employed

(Fig.2.1.d)

26

a. Age wise (in years) distribution of the

respondents

b. Educational qualification of the respondents

c. Monthly income of the respondents d. Occupational status of the

respondents

Fig. 2.1 Socio-economic profile of the selected respondents

27

Table 2.2

Educational and economic status of the selected respondents (N=300)


Educational qualification

Illiterate 18.00

Primary school 12.00

Higher secondary 33.00

High school 16.33

Graduate 20.66

Monthly income (Rs.)

<2500 18.3

2501-4500 09.7

4501-7500 22.0

>7501 50.0

Occupational status

Housewife 71.33

Labourer 22.33

Self-employment 06.33

2.3.2 Consumption pattern of breakfast among the selected respondents

Details about breakfast items preferred and consumed by the selected population are

shown in Table 2.3. It was found that 85 per cent consumed breakfast regularly and

fifteen per cent of the selected population has shown to skip breakfast. In the study done

by Agostoni et al., (2010) it was reported that nearly 10-30 per cent of the breakfast

skippers are found throughout the world which is in par with the current study.

28

Table 2.3

Details on breakfast consumption (N=300)


Breakfast intake

Eating breakfast 84.66

Skipping breakfast 15.33

Items preferred

Idli 69.30

Dosa 21.00

Oats 09.70

Items consumed

Idli 25.00

Dosa 20.00

Chapathi 18.00

Noodles 13.85

Poori 12.15

Oats porridge 05.40

Bread 05.60

Studies done by Reddy et.al (1981) and Balasubramanian and Viswanathan (2007a)

showed that idli is a breakfast food and the current study reassures the same with 69 and

21 per cent of the selected population preferring to take idli and dosa respectively as

breakfast item daily . Further it was noted that only 25 per cent consume idli daily and 20

per cent consume dosa daily. The interesting fact is that 99 per cent of the respondents

have a liking for idli as breakfast.

29

2.3.3 Preparation of idli at household level

In spite of 71 per cent being housewives among the selected population, Table 2.4

revealed that only seven per cent of the population grind idli batter at home daily whereas

majority (58.33%) grinds only once in a week (Fig.2.2.a). Most of the respondents reveal

it due to the reason that grinding idli batter is laborious. For idli making majority of the

population (68%) prefer parboiled rice (Fig.2.2.b).

Table 2.4

Idli preparation at household level (N=300)


Frequency of grinding idli batter

Daily 07.00

Once in a week 58.33

Twice in a week 28.66

Once in a month 06.00

Variety of rice

Parboiled rice 68.03

Ration rice (provided at PDS) 19.30

Mixed rice 12.66

Type of black gram dhal

Husk removed (decorticated) 34

Husk removed after soaking 49

Both 17

Ratio of rice: black gram dhal

3:1 99.70

8:1 00.30

30

Only 34 per cent used decorticated black gram whereas 49 per cent used black gram with

husk after soaking (Fig.2.2.c). Ratio of the raw ingredients in idli making is an important

criterion for the texture of the idli. In the current study majority (99.7%) of the

respondents used 3:1 ratio of rice and black gram dhal respectively. The findings

regarding the preparation of idli at house hold level is supported by the study done by

Balasubramanian and Viswanathan (2007b) who reported that idli batter was prepared

from soaking polished parboiled rice and decorticated black gram for 4 hour at 30±1C in

water and the soaked ingredients were ground to 0.5-0.7-mm particle size batter using

wet grinder with adequate amount of water. The blend ratios of 2:1, 3:1, 4:1(v/v) batter

were allowed for fermentation adding two percent of salt. From the survey it was also

found that 100 per cent of the respondents added fenugreek as an additional ingredient in

idli making.

Generally after grinding idli batter, the batter is left for fermentation. Fermentation time

varied between 5 h to 12 h at the selected households (Table 2.5 and Fig.2.3.a). Majority

(71.3%) of them fermented the idli batter for 11 to 12 h. The texture of idli is influenced

by many variables like raw material, quantity, soaking time, grinding conditions,

fermentation time and temperature are adjuncts on quality of idli (Desikachar et al.,

(1960) and Radhakrishnamurthy et al., (1961). Fermentation of idli batter is an essential

step because as reported by Mukherjee et al., (1965), Rajalakshmi and Vanaja (1967) the

microorganisms present in black gram dhal helps in acidification and leavening of the

batter by which gas, acid and several volatile compounds are formed during fermentation

which contribute to a complex blend of flavours in the products (Chavan and Kadam,

1989). The household measures to control fermentation of idli batter to extend the shelf-

life are shown in Table 2.5 and Fig.2.2.b. Majority (73%) stored the idli batter in

refrigerated condition, 19 per cent store idli batter over water tub, and rest of the selected

population place betel leaves (4.33%), lady‘s finger (1.66%) and coconut slices (1%)

over the idli batter respectively. The scientific reasons for these measures expect for

refrigeration is still in dark.

31

Fig. 2.2 Details on idli preparation at household level

b. Variety of rice used by respondents for making idli

c. Type of black gram dhal used for idli making

a. Frequency of grinding idli batter at house hold level

32

a. Fermentation time of batter at household level b. Measures to control fermentation at household level

Fig.2.3 Details on fermentation time and measures to fermentation

33

Table 2.5

Fermentation time and measures followed to control fermentation

of idli batter at households (N=300)


Fermentation time (h)

05-06 04.30

07-08 00.70

09-10 23.70

11-12 71.30

Measures to control fermentation

Refrigerator 73.33

Placing over water 19.33

Betel leaves 04.33

Lady‘s finger 01.66

Coconut slices 01.00

Plantain leaves 00.33

2.3.4 Preference for commercial idli batter against home-made batter

From Table 2.4 it was discussed that only seven per cent of the selected population

ground idli batter daily, but Table 2.3 show that 45 per cent of the selected population

consume idli and dosa every day for breakfast. This is because 49 per cent of the

respondents have shown interest to purchase ready to cook idli batter every day (Table

2.6). The cost variation of the commercial idli batter may be due to the quality of

ingredients used and the type of packaging. Majority (31.3%) purchase batter which

range between Rs. 10 to Rs.12, 26 per cent purchase between Rs. 13 to Rs.16. Regarding

colour of the commercial idli batter majority (59%) of the selected population expressed

that the colour was pale and unappealing and 64 per cent criticized that the commercial

34

idli batter had thin consistency which gave poor quality of idli and so it was used for dosa

making.

Table 2.6

Details about purchase of commercial idli batter (N=300)


Frequency of purchase

Daily 49.3

Weekly 21.0

Monthly 19.7

Cost in rupees

7-9 16.3

10-12 31.3

13-16 26.3

17-20 14.7

21-30 00.7

Nil 10.7

Colour

Bright 41.00

Pale 58.99

Consistency

Thick 35.33

Thin 64.00

Preference

Like 47.23

Dislike 52.77

35

Among the selected population 53 per cent disliked commercial idli batter especially for

its aroma, out of which 31 per cent expressed problems regarding quality and shelf-life of

the batter. The study revealed that all the respondents (100%) will purchase ready to cook

idli batter if the batter quality, fermented aroma and shelf-life are improved.

2.4 CONCLUSION

The results of the survey indicates the practices currently followed by the population, not

statistically representative is similar to the practices reported in literature such as variety

of rice, type of black gram, ratio of ingredients used for idli making, fermentation time

and shelf –life of the batter.

36

TEXTURE OPTIMIZATION OF IDLI

3.1 INTRODUCTION

Indigenous or native fermented foods have been prepared and consumed for thousands of

years, and are strongly linked to culture and tradition. The fermented foods are better in

terms of nutrition and easy for digestion than the normal cooked foods. The fermentation

process causes enrichment and improvement of food through flavour, aroma, and change

in texture, preservation by providing organic acids, nutritional enrichment, reduction of

exogenous toxins and reduction in the duration of cooking. During traditional

fermentation process, locally available ingredients, which may be of plant or animal

origin, are converted into edible products by the physiological activities of

microorganisms and have distinct odour (Steinkraus 1996, Reddy and Salunkhe 1980)

namely Lactobacillus sp. and Pediococcus sp. which produce organic acids such as lactic

acid and acetic acid, alcohol and carbon dioxide (Caplice and Fitzgerald 1999) and

reduce the pH, thereby inhibiting the growth of food spoiling microorganisms. These

fermented foods can be preserved for several days (Tamang, 1998) and also have

therapeutic properties (Sekar and Mariappan, 2007). There are different types of

fermented foods in which a range of different substrates are metabolized by a variety of

microorganisms to yield products with unique and appealing characteristics (Caplice and

Fitzgerald 1999). Among all traditional fermented foods in India, idli is a white,

fermented (acid leavened), steamed, soft and spongy texture product, widely popular and

consumed in the entire South India. Idli is the resultant product from the naturally

fermented batter made from washed and soaked rice (Oryza sativa L.) and dehusked

black gram dhal (Phaseolus mungo L.). Apart from its unique texture properties, idli

makes an important contribution to the diet as a source of protein, calories and vitamins,

especially B-complex vitamins, compared to the raw unfermented ingredients (Reddy et

al., 1982).

Traditionally, rice and black gram in various proportions are soaked and ground adding

water in mortar and pestle to yield a batter with the desired consistency. Parboiled rice is

preferred over raw rice for idli and dosa with rice: black gram usually fermented at 3:1

37

(Steinkraus et al, 1967, Jama and Varadaraj, 1999) weight ratio for making soft and

spongy textured idli (Nazni and Shalini 2010). Black gram, the leguminous component of

idli batter, serves not only as effective substrate but also provides the maximum number

of micro-organisms for fermentation (Balasubramanian and Viswanathan, 2007a). As a

result of fermentation, (Padhye and Salunkhe, 1978) observed a significant increase in

predicted biological value. Fermentation also improves the protein efficiency ratio (PER)

of idli over the unfermented mixture (Van Veen et al, 1967).

Idli preparation in the conventional manner takes at least 18 h. The available instant idli

pre-mixes do not provide the desired textural characteristic and also lack the typical

fermented aroma and on the other hand, idli prepared in different households do not have

consistent quality (Nisha et al, 2005). Fermented foods in general have immense scope

for commercialization as foods with improved nutritional value as well as functional

foods. Fermented foods with scientifically developed starter cultures can aid the

commercialization of these products. However scientific optimization of the process is

the basic necessity for commercialization of any product including the fermented foods.

Several researchers have used RSM successfully to optimize the conditions for making

products like boondi (Ravi and Susheelamma, 2005), tandoori roti, puri and parotta

(Saxsena and Haridasrao, 1996 and Vatsala 2001) .The current study is undertaken to set

an optimized condition for the preparation of idli which will help the manufacturers at

industrial level to produce idli with the desired textural property. This would also help to

make proprietary products using proper starter culture. The main objectives of this study

were to explore the effect of rice and black gram dhal and fermentation time on the

texture of idli, analyzing the instrumental texture profile (TPA) parameters as a function

of raw material composition and fermentation time and to find the optimum levels to

maximize the desirable textural properties of idli using RSM.

38


3.2.1 Materials

Different rice varieties namely IR 20 idli rice, raw rice, broken rice, ration rice and red

rice were procured from local market and black gram variety Aduthurai 3 (ADT3) which

has 24.16 per cent protein content was procured from Tamil Nadu Rice Research

Institute (TRRI), Aduthurai, Tamil Nadu, India. They were cleaned and stored at

refrigerated conditions until use.

3.2.2 Preparation of idli

Before framing the design using CCRD, preliminary trails were conducted to choose the

ratios of rice to black gram dhal. The trails were done using the rice to black gram dhal

ratios as 3:0.5, 3:1, 3:1.5, 3:2, 3:2.5 and 3:3 respectively where rice ratios were kept

constant and the dhal ratios varied. The fermentation time varied between 10 to 14h. In

the trial, idli made from the ratio 3:1 and 3:1.5 with a fermentation time between 11 to 12

h gave better results. Based on this, the maximum and minimum values for the

independent variables were chosen to frame the model. The rice and black gram dhal

were mixed at different ratios as per the CCRD (Table 2.1). The rice and dhal were

soaked for 4 h and ground separately to a coarse consistency and mixed together with

salt. The batter was left overnight (time based on the developed design) for fermentation.

The fermented batter was mixed thoroughly to expel the gas formed due to the release of

carbon-dioxide .The batter was poured in idli mould, and steamed in the idli steamer for

15 minutes. The idli were brought to room temperature and then used for instrumental

texture profile.

3.2.3 Experimental design

3.2.3.1 Response surface Methodology

RSM is a collection of statistical and mathematical techniques useful for developing,

improving, and optimizing processes in which a response of interest is influenced by

several variables and the objective is to optimize this response. RSM has important

39

application in the development and formulation of new products, as well as in the

improvement of existing product. It helps to study the effect of the independent variables,

alone or in combination, on the responses. In addition to analyzing the effects of the

independent variables, it provides a mathematical model, which describes the

relationships between the independent and dependent variables (Myers and Montgomery,

1995). RSM has been very popular for optimization studies in recent years. RSM reduces

the number of experiment trials needed to evaluate multiple parameters and their

interactions. The graphical perspective of the mathematical model has led to the term

Response Surface Methodology. Generally an optimization study involving RSM has

three stages. The first stage is the preliminary experimental trials, in which the

determination of the independent variables and their limits are carried out. The second

stage involves the selection of appropriate experimental design followed by prediction

and verification of the model equation. The last stage is the generation of response

surface plots as well as contour plots of the responses as a function of the independent

parameters and determination of optimum conditions. The model used in RSM is

generally a full quadratic equation or the diminished form of the equation. The second

order model can be written as Eqn.1.

where Y is the predicted response, β0, β j, β jj and β ij are regression coefficients for

intercept, linear, quadratic and interaction coefficients respectively, k is the number of

independent variables and Xi and Xj are coded independent variables.

Response surface methodology has been widely applied in the food industry optimizing

complex processes and products (Wong et al, 2003, Lee et al, 2006 and Sin 2006). In the

present study RSM was used to determine the optimum conditions of two independent

variables (rice to black gram dhal ratio and fermentation time) on the TPA and colour

attributes of idli. A CCRD was constructed using software package Statistica (1999) from

StatSoft, OK, USA. Five levels of each predictor variable were incorporated into the

developed design. Table 1 shows levels of predictor variables.

…………….Eqn. 1

40

3.2.3.2 Optimization of idli

The procedure was based on the hypothesis that quality attributes of idli were

functionally related to rice to black gram dhal ratio and fermentation time, and attempts

were made to fit multiple regression equations describing the responses. Two coded

independent variables in the process were rice to black gram dhal ratio (X1) and

fermentation time (X2). Five levels of each of the independent variable were chosen for

the study (Table 3.1); thus, there were 13 combinations, including the replicates of the

center point that were performed in random order, based on an experimental CCRD for

two factors. The dependent variables were hardness, adhesiveness, springiness,

cohesiveness, chewiness and resilience and colour attributes.

Table 3.1

Central composite rotatable design: Coded and actual values of independent

variables

Experimental

design points

Rice : black gram Ratio

(w / w)

Fermentation time

(h)

Actual Coded

Actual Coded

1 3 : 0.72 -1.000 10.58 -1.000

2 3 : 0.72 -1.000 13.42 1.000

3 3 : 1.78 1.000 10.58 -1.000

4 3 : 1.78 1.000 13.42 1.000

5 3 : 0.50 -1.414 12.00 0.000

6 3 : 2.00 1.414 12.00 0.000

7 3 : 1.25 0.000 10.00 -1.414

8 3 : 1.25 0.000 14.00 1.414

9 3 : 1.25 0.000 12.00 0.000

10* 3 : 1.25 0.000 12.00 0.000

*Centre point repeated 3 times

3.2.3.3 Instrumental Colour Measurement

The colour parameters of idli were measured using a Hunter Lab colour flex model A60-

1012-312 (Hunter Associates laboratory, Reston, VA). The equipment was standardized

each time with white and black standards. Samples were scanned to determine lightness

(L*), red-green (a*) and yellow-blue (b*) colour components (Olajide, 2010). As in the

41

work done by (Ronald and Daniel, 1998) the hue angles were derived as the arctangent of

b*/a* expressed as degrees and the chroma values were also calculated as the square root

of the sum of the squared values of both CIE a* and CIE b*.

The chroma and Hue angle were calculated by the formula Eqn.2 and Eqn. 3,

respectively.

Where a* indicated Red-Green colour components, while b* indicates yellow to blue

colour components (Ali, 2008).Plate 3.1 shows the picture of colour flex.

Plate 3.1 Color flex

3.2.3.4 Texture profile analysis (TPA)

The TPA test consists of compressing a bite-size piece of idli two times in a reciprocating

motion that imitates the action of the jaw. The idli was cooled to room temperature and

was cut into an inch cube (Plate 3.3) using an inch cubic mould (Plate 3.2.a). The texture

of each idli was analyzed using SMS/75mm (Plate 3.2.b) compression platen in Texture

…………….Eqn. 2

…………….Eqn. 3

42

Rice (IR20 idli rice) and Black

gram dhal (ADT3) (ratio based

on the experimental design)

Soak (4h) and grind

Pour batter in idli mould and steam

for 15 minutes

Ferment the ground batter (Based

on the experimental design)

Cool idli to room temperature and

cut the centre using one inch cubic

mould

TPA of cut idli using SMS/75mm

compression platen

Statistical Analysis

(RSM; Regression)

43

Fig.3.1 Flow chart showing work design for TPA of idli

Analyzer (Stable Micro Systems, Surrey,UK). The extra top and bottom layers were

sliced off to make the idli fit to the mould. The cut piece was placed on the heavy duty

platform and the test speed was set to 5mm/sec and the probe compressed 50% of the idli

to get the TPA of the idli. Based on the force deformation curves, several parameters like

adhesiveness, springiness, cohesiveness, chewiness and resilience can be calculated.

Plate 3.2 Cutting idli with the designed mould

44

Plate 3.3 One inch cubic mould and SMS/75mm compression probe

Plate 3.4 Texture analyzer

a)

b)

45

3.2.4 Statistical Analysis

The independent variables and dependent variables (responses) were fit to the second-

order polynomial function and examined for the goodness of fit. The R2 or coefficient of

determination is defined as the ratio of explained variation to the total variation and is a

measure of the degree of fit (Haber and Runyon, 1997). All experimental designs and

statistical data were analyzed and response surfaces, ANOVA, regression analysis were

reported using Statistica (StatSoft, OK, USA) statistical software.


The results of chapter 3 are discussed under the flowing heads:

3.3.1Effect of rice varieties on rice batter volume

3.3.2 Effect of black gram on batter volume

3.3.3 Effect of ratios of rice to black gram dhal on batter volume

3.3.4 Response surfaces

3.3.5 Instrumental Colour measurement of idli

3.3.6 Texture parameters

3.3.7 Simultaneous optimization

3.3.1 Effect of rice varieties on rice batter volume

In the present study five varieties of rice namely ration rice, raw rice; broken rice, red rice

and parboiled rice were used for idli making. The rise in CO2 production can be

correlated with the increase in batter volume (Sridevi et al., 2010).The percentage of

increase in batter volume was significant (p< 0.05) in the batter prepared with ration rice,

followed by parboiled rice, raw rice, broken rice, and red rice. Though there is high

increase in batter volume, after expulsion of gas the volume of batter gets significantly

decreased in ration rice, whereas the batter volume did not show significant (p< 0.05)

decrease in parboiled rice. Table 3.2 and Fig 3.2.a shows the effect of rice varieties on

batter volume. The sensory score of idli showed variation with the variety of rice used.

As the idli prepared from parboiled rice is very soft when compared with idli made with

other varieties. Parboiled rice may be best suited for idli making which is in par with the

46

result reported by Juliano and Sakurai (1985) that parboiled rice is better suited than raw

rice for producing idli , i.e., it is soft without becoming sticky. The idli prepared using

very light coloured parboiled rice are preferred by consumers traditionally accustomed

to eating raw rice. Sowbhagya et al., (1991) studied the effect of variety, parboiling and

ageing of rice on the quality of idli and reported that the normal parboiled rice is best

suited for making idli as shown by its higher scores for softness. In the present study the

idli made of parboiled rice is soft and it may also be due to fact proved by Sharma et al.,

(2008) that the greater starch damage in parboiled rice during wet grinding, attribute to its

greater susceptibility to undergo damage owing to its softness after soaking as well as to

the longer duration of grinding favouring parboiled rice to be suited for idli making. Roy

et al., (2010) noted that the hardness and adhesion of cooked rice were dependent not

only on the moisture content but also on the forms and variety of rice. Roy et al., (2004),

Roy et al., (2008), Islam et al., (2001) and Shimizu et al., (1997) reported that the

hardness of the cooked rice depend on the moisture content of cooked parboiled and

untreated rice. In case of idli, steaming increases the moisture content of idli and it is a

major factor that makes idli made with parboiled rice softer and for the same reason that

red rice has acquired more moisture which affected its texture losing firmness.

3.3.2 Effect of black gram on batter volume

The percentage of increase in batter volume was significant (p< 0.05) at five per cent

level (Table 3.3) for the batter made from parboiled rice and black gram used with husk,

and thou the idli made from the same batter were spongy, the colour was unappealing to

the panel members. The difference in batter volume was not significantly higher with the

batter made from the black gram with husk removed. On the other hand, though, the

percentage of increase in batter volume was low (38.9%) in the batter made from

parboiled rice and black gram dhal with husk removed after soaking,

47

Table 3.2

Effect of rice varieties on the batter volume after fermentation

mean values in a row with different letters differ significantly p<0.05 by LSD (n=3)

the texture was very spongy and the colour was also appealing making this variation a

better choice in terms of colour and texture on sensory basis. Fig 3.2.b shows the effect of

variation in black gram dhal on batter volume.

3.3.3 Effect of ratios of rice to black gram dhal on batter volume

The percentage of increase in batter volume was high for the ratio 3:3.5 (w/w) of rice to

black gram dhal respectively with 5% significance followed by other ratios such as 3:3,

3:2.5 and so on. When the texture of idli was compared on sensory basis, the idli made

of ratio 3:1 was very spongy compared to idli made of other ratios of rice and black gram

dhal showing that the proportions of compositions of the substrate also have an important

role in the outcome of the product. Table 3.4 and Fig 3.2.c shows the effect of ratios of

ingredients on batter volume. Hence for the further study parboiled rice namely IR 20,

black gram variety namely ADT 3 with husk removed after soaking was used to find the

effect of ingredients and descriptive sensory profile of idli.

Batter characteristics

Varieties of rice

Parboiled

rice

Ration

rice

Raw

rice

Broken

rice

Red

rice

Initial volume of the batter (cm3)

221.6 ±2.05 d

211.1±1.55 b 218.6±0.98 c 200.5±0.14 a 238.2±0.14 e

Final volume of the batter (cm3)

306.1± 3.74 e

299.7±1.41 d 275.8±2.61 b 248.8±2.61 a 293.7±3.53 c

Batter volume increased after

fermentation (%) 38.1±1.27 c 42.0±0.70 d 26.2±0.35 b 24.1±0.21 a 23.3±0.28 a

Volume of the batter after

expulsion of gas (cm3)

202.0±0.56 e 150.8±0.84 a 181.0±0.70 c 193.0±1.83 d 158.0±1.41 b

Batter volume decreased after

expulsion of expulsion of gas (%) 34.0±1.41 b 49.7±0.00 d 34.4±0.63 b 22.4±1.41 a 46.1±0.0 c

Sensory Rank I IV II III V

48

Table 3.3

Effect of black gram (var. ADT 3) on the batter volume after fermentation

Mean values in a row with different letters differ significantly p<0.05 by LSD (n=3)

BHR-black gram husk removed; BHRAS-black gram husk removed after soaking; BWH -black gram with husk

Table 3.4

Idli batter volume characteristics as affected by parboiled rice

and black gram dhal (without husk)

Mean values in a row with different letters differ significantly p<0.05 by LSD (n=3)

Batter characteristics

Black gram

BHR

BHRAS BWH

Initial volume of the batter (cm3)

263.8±0.14 b 271.4 ±0.14 c 226.1 ±0.84 a

Final volume of the batter (cm3)

339.2±0.131 b 376.9 ±0.07 c 324.1 ±0.00a

Batter volume increased after

fermentation (%)

28.6 ±0.00 a

38.9 ±0.07 b

043.3 ±0.07 c

Volume of the batter after

expulsion (cm3)

248.7 ±0.35 b

256.3 ±0.42 c

211.1 ±0.07 a

Batter volume decreased after expulsion

of gas (%)

26.7 ±0.00 a

32.0 ±0.00 b

34.9±0.14 c

Sensory Rank II I III

Batter

characteristics

Rice and black gram ratio (w/w)

3 : 1

3 : 1.5 3 : 2 3 : 2.5 3 : 3 3 : 3.5

Initial volume of the

batter (cm3)

150.7 ±0.07a 241.2±0.28c 301.5±0.21d 324.1 ±0.14e 339.2 ±1.13f 414.6 ±0.07g

Final volume of the

batter (cm3)

248.7±1.13a 316.6 ±0.84c 422.7 ±0.07d 452.3 ±0.07e 467.4 ±0.00f 603.1 ±0.07g

Batter volume

increase after

fermentation (%)

65.0 ±0.0a

31.3 ±0.07c

40.2 ±0.07d

39.6 ±0.28e

37.8 ±0.35f

45.5 ±3.0.07g

Volume of the batter

after expulsion (cm3)

158.3 ±0.21a

173.4 ±0.0b

233.7 ±0.14d

248.7 ±0.28e

256.3 ±0.14f

301.5 ±0.0g

Batter volume

decrease after

expulsion of gas (%)

36.3 ±0.28b

45.2 ±0.28d

44.7 ±0.28c

45.0 ±1.41d

44.2 ± 1.13c

50.0±0.14e

Sensory Rank I III II IV V VI

49

Fig.3.2.c Effect of ratios of rice to black gram dhal on batter volume after

fermentation

Fig.3.2.a Effect of rice varieties on batter volume after fermentation

Fig.3.2.b Effect of type of dhal on batter volume after fermentation

50

3.3.4 Response surfaces

Several parameters namely raw material variety, quality, their proximate composition,

raw material composition, particle size, temperature etc., affect the texture of idli but still,

the texture of idli is very unique from the consumer point of view. Among all the

parameters mentioned, fermentation time is one of the key factors which can affect the

texture due to its air production and leavening action. The texture of the cooked idli is a

subject of interest, to judge and optimize the production process of good textured idli

with the selection of the ingredients and the process. The fermentation periods are

slightly different for idli making owing to the difference in raw materials, composition,

process and region (Balasubramanian and Viswanathan, 2007b).

3.3.5 Instrumental Colour measurement of idli

Colour of the idli is one of the most important parameter for the acceptability of the

product. The colour of the idli showed variation based on the ratio of rice and black gram

dhal used. The L*, a*, b* values and graph are shown in Table 3.5 and Fig.3.3.a, b, c

respectively. The L* value which correspond to lightness ranged from 73.40 to 75.99

indicating the difference in the proportion of black gram dhal used. The positive values of

b* indicates yellowness in the idli, which may be due to the use of black gram with husk

for soaking. The chroma (Fig.3.3.d) values are closer to the b* values. The hue angle

value corresponds to whether the object is red, orange, yellow, green, blue, or violet (Ali

et al, 2008). The negative values in the hue angle shows that the product deviates from

the colour adding positive factor to the current study because lightness in the colour of

the idli is an important factor in the view of customer perception. The intensity of chroma

is low for the idli made with the ratio of 3:0.5 and is higher for the idli made from the

ratio 3:2 showing that the ratio of rice and dhal used for idli making has an impact on the

intense of chroma of the idli.

51

Table 3.5

Experimental design: CCRD with actual levels of independent variables for colour

parameters

*Centre point replicated 3 times

Experimental

design points

Instrumental colour parameters

L* a* b* Chroma Hue angle

(°)

1 74.03 + 0.07 -0.44+0.021 11.52+ 0.064 11.56 -87.72

2 74.13 + 0.07 -0.57+0.007 10.60+0.035 10.59 -86.92

3 75.76 + 0.11 -0.25+0.028 12.21+0.085 12.15 -88.92

4 73.99 + 0.06 -0.24+0.021 13.57+0.007 13.56 -89.03

5 75.57 + 0.07 -0.76+0.035 10.01+0.360 9.936 -85.79

6 75.78 + 0.03 -0.02+0.070 15.97+0.085 16.03 -89.89

7 73.40 + 0.11 -0.43+0.014 13.09+0.177 12.96 -88.14

8 74.32 + 0.51 -0.13+0.014 11.88+0.205 11.74 -89.14

9 74.35 + 0.11 -0.40+0.007 10.56+0.163 10.44 -87.81

10* 74.36 + 0.05

-0.43+0.028 10.61+0.361 10.35 -87.73

52

Fig. 3.3.a. Response surface graph showing relation between independent parameters on L*

Fig. 3.3.b Response surface graph showing relation between independent parameters on a*

53

Fig.3.3.c Response surface graph showing relation between independent parameters on b*

Fig.3.3.d Response surface graph showing relation between independent parameters on Chroma

54

3.3.6 Texture parameters

The experimental values for the response variables of texture analysis are shown in Table

3.6. Figure 3.4.a and Figure 3.4.b shows the typical TPA graph. Hardness of idli is

indicated by the maximum force required to compress the idli and usually represented by

the first peak in the graph. The hardness of the idli (Fig.3.5.a) varies between a minimum

force of 20.58 N to a maximum force of 44.19 N i.e., the minimum force was required to

compress idli of ratio 3:0.72 at 13.42 h fermentation time and the maximum force for the

ratio 3:1.78 at 10.58 h of fermentation time. This variation in the force is due to the

variation in the ratio of the ingredients and fermentation time of the batter. Higher the

force shows that harder is the idli. ANOVA results indicated that the ratio of rice and

black gram dhal used for idli making (in the linear effect) is significant (P< 0.05) to the

hardness of the idli. The co-efficient of regression is given in Table 3.7. The goodness of

fit was high with R2 value =0.942.

Adhesiveness of idli can be defined as the negative force area for the first bite and

represents the work required to overcome the attractive forces between the surface of the

cut piece of idli and the surface of the probe with which the idli comes into contact, i.e.

the total force necessary to pull the compression plunger away from the food. The

negative area in the graph is taken as the adhesiveness. The adhesiveness of the idli varies

between -0.00051N s to -0.05127 N s. If the product is sticky, the adhesiveness will be

higher. Ghasemi et al, (2009) reported that the adhesiveness may be due to the

gelatinization and more fluidity of rice starch structure in the cooked samples. As idli is

adhesive in nature, to optimize the product minimum adhesiveness can be considered. In

the current study since the batter was coarse ground and cooking time was constant the

adhesiveness must be due to the ratio of rice and dhal and the quality of the ingredient.

The minimum adhesiveness is obtained for the idli made of ratio 3:0.5 at 12 h

fermentation time and the maximum adhesiveness is obtained for the ratio 3:0.72 at

10.58h fermentation time. Fig. 3.5.b shows the response surface graph for adhesiveness.

55

Fig.3.4.a Texture profile of idli made of ratio 3:1.25 at 12 h fermentation time

Fig.3.4.b Texture profile of idli made of ratio 3:2 at 12 h fermentation time

Force (N)

Force (N)

Time (sec)

Time (sec)

56

Table 3.6

Experimental design: CCRD with coded and actual levels of independent variables

for TPA

Experi

mental

design

point

Dependent variables

Hardness

(N)

Adhesiveness

(N s)

Springiness Cohesiveness Chewiness Resilience

1 23.73±2.01 -0.0512±0.0045 0.926±0.33 0.876±0.12 1963.61± 16.26 0.595 ± 0.12

2 20.58±1.42 -0.0337±0.0038 0.960±0.28 0.819±0.04 1650.89±14.05 0.562 ± 0.52

3 44.19±2.02 -0.0284±0.0042 0.809±0.41 0.643±0.09 2344.08±21.01 0.340 ± 0.41

4 36.57±2.24 -0.0005±0.0037 0.847±0.20 0.674±0.07 2127.97±16.42 0.404 ± 0.24

5 20.66±3.52 -0.0051±0.0069 0.854±0.32 0.912±0.17 1845.66±18.01 0.654 ± 0.42

6 32.47±4.13 -0.0290±0.0053 0.965±0.48 0.825±0.02 2333.37±14.01 0.511 ± 0.54

7 35.36±1.41 -0.0085±0.0075 0.733±0.24 0.526±0.04 1389.17±13.32 0.285 ± 0.10

8 24.12±2.14 -0.0008±0.0061 0.916±0.42 0.755±0.04 1701.18±12.42 0.483 ± 0.27

9 30.85±0.05 -0.0062±0.0047 0.928±0.31 0.876±0.02 2557.13±11.14 0.579 ± 0.13

10* 30.72±1.28 -0.0057±0.0039 0.913±0.31 0.885±0.06 2532.79±15.05 0.574 ± 0.41

*Centre point replicated 3 times

Springiness is the height that the idli recovers during the time that elapses between the

end of the first bite and the start of the second bite, usually in TPA the first compression

and second compression. The difference between the first peak and the second peak in

the graph is taken as springiness. The springiness of idli depends on the quantity of the

dhal used because the soft spongy texture observed in the leavened steamed idli made

out of black gram is due to presence of two components, namely surface active

protein (globulin) and a polysaccharide (arabinogalactan) in black gram (Susheelamma

and Rao 1974, 1979a, 1979b, 1980). The specialty of black gram in idli preparation is due

to the mucilaginous property which helps in the retention of carbon-dioxide evolved

during fermentation (Nazni and Shalini, 2010). In the current study the springiness

varied from 0.733 to 0.965. The maximum springiness is obtained for the ratio 3:2 at 12 h

57

fermentation time. Hence the result reveals that the quantity of black gram dhal used has

a major role in the springiness of the idli. The response surface graph in 3D is depicted in

Fig.3.5.c showing the relation between rice to black gram dhal ratio and fermentation

time on springiness. From the ANOVA table it is clear that the independent variables in

the linear effect showed a significant influence on the springiness of the idli and the

model showed high goodness of fit (R2 = 0.909) .

Cohesiveness is defined as the ratio of the positive force area during the second compression to

that during the first compression. Cohesiveness may be measured as the rate at which the material

disintegrates under mechanical action. The cohesiveness is minimum (0.526) for the ratio

3:1.25 at 10 h fermentation time and maximum (0.912) for the ratio 3:0.5 at 12 h

fermentation time. Both the independent variables namely rice to black gram dhal ratio

in linear effect and fermentation time in quadratic effect is significant at 5 % level on the

cohesiveness of the idli. The graph in Fig.3.5.d shows an initial increase in the

cohesiveness as the fermentation time increases, but gradually decreases with further

increase in fermentation time.

58

Fig.3.5.a Response surface graph showing relation between independent parameters on hardness

Fig.3.5.b Response surface graph showing relation between independent parameters on adhesiveness

59

Fig.3.5.c Response surface graph showing relation between independent parameters on springiness

Fig.3.5.d Response surface graph showing relation between independent parameters on cohesiveness

60

Fig.3.5.e Response surface graph showing relation between independent parameters on Chewiness

61

Fig.3.5.f Response surface graph showing relation between independent parameters on resilience

62

Table 3.7

Regression co-efficient for dependent TPA parameters

L - Linear effect; Q - Quadratic effect; *=P < 0.05

Table 3.8

Analysis of Variance (ANOVA) for dependent TPA parameters: F values

L - Linear effect; Q - Quadratic effect; *=P < 0.05

Chewiness is defined as the product of hardness x cohesiveness x springiness and is

therefore influenced by the change of any one of these parameters. Lower the chewiness

softer is the idli. The chewiness of the idli varied between 1389.172 for the ratio 3:1.25

at10 h fermentation time to 2557.135 for the ratio 3:1.25 at 12 h fermentation time. It is

proved by the ANOVA table (Table 3.8) that the ratio of rice to black gram dhal in linear

effect and fermentation time in quadratic effect also have significant impact (P < 0.05)

Independent

variables

Regression Co-efficient

Hardness Springiness

Cohesiveness

Chewiness

Resilience

Mean/Interaction 34.390 -2.254 -5.873 00.00 -4.602

1. Rice : Dhal ratio (L) 31.132 -0.182 -0.529 661.94 -0.603

Rice : Dhal ratio (Q) 1.981 -0.001 -0.049 -378.64 -0.003

2. Fermentation time (L) -3.517 0.525* 1.161* 4241.93* 0.906*

Fermentation time (Q) 0.147 -0.021 -0.049* -178.51* -0.038*

1L by 2L -1.645 0.008 0.042 63.76 0.036

R2

0.942 0.908 0.886 0.85 0.931

Independent

variables

Dependent parameters

Hardness Springiness Cohesiveness Chewiness Resilience

1. Rice : Dhal ratio (L) 000.000 15.644* 12.755* 11.161* 0.524*

Rice : Dhal ratio (Q) 241.174* 0.001 0.228 1.134 96.244

2. Fermentation time (L) 000.000 15.404* 5.074 0.487 3.823*

Fermentation time (Q) 063.752 7.401 11.447* 12.628* 2.724*

1L by 2L 1050.770* 0.138 1.027 0.198 31.967

63

on the chewiness of the idli. As hardness, springiness and cohesiveness show significant

influence because of the independent variable hence the chewiness of the idli will also be

affected by the both independent and dependent variables. The chewiness (Fig.3.5.e) of

the idli varied for the same ratio of idli with difference in fermentation time which relates

the decrease in cohesiveness with further increase in fermentation time.

Resilience is a measurement of how the sample recovers from deformation both in terms

of speed and forces derived. It is taken as the ratio of areas from the first probe reversal

point to the crossing of the x-axis and the area produced from the first compression cycle.

The resilience varies between 0.285 for the ratio 3:1.25 at 10 h fermentation time to 0.654

for the ratio3:0.50 at 12 h fermentation time. Lower resilience value shows that the

product can recover faster from deformation proving the firmness of the product. The

response surface graph in 3D is depicted in Fig.3.5.f showing the relation between rice to

black gram dhal ratio to fermentation time on resilience of the idli. From the ANOVA

table it is evident that the resilience of the idli is influenced significantly by rice to black

gram dhal ratio in linear effect and by fermentation time both linear and quadratic effect.

The closer the value of R2 approaches unity, the better the empirical model fit the actual

data (Nuraliaa et al., 2010). As the R2 value for resilience (0.932) was closer to unity and

the result of resilience fit to the actual data.


Simultaneous optimization was performed on the TPA parameters like hardness,

adhesiveness, springiness, cohesiveness, chewiness and resilience by imposing

desirability constraints. In case of springiness, the softer idli shows high springiness.

Hence the software take into account of the values of independent and dependent values

and finally gives a maximum desirable score and the condition at which the maximum

score can be obtained with some constraints by assigning maximal desirability score as

one and minimal desirability score as zero. Table 3.9 shows the constraints imposed for

good textured idli with the desirable value for both independent and dependant variables.

The maximum desirable score that can be achieved with the desirable value will be

0.8279. On the basis of these calculations good textured idli could be made when 3:1.575

64

(mass) ratio of rice to black gram dhal respectively is fermented for 14 h. The optimum

results were validated by performing the experiment at the optimized ratio and

fermentation time by comparing the observed and the predicted values. The predicted

values are shown in Table 3.9. The predicted values were insignificant with observed

values indicating the appropriateness of the model developed.

Table 3.9 Simultaneous optimization of process parameters by desirability approach

3.4 CONCLUSION

The optimization results indicated that the optimum ratio of rice to black gram dhal is

3:1.575 (w/w), with 14 h of fermentation time will provide the product with maximum

score for desirable textural parameters.

Independent parameters Dependent variables

Overall

Desirability

score

Rice : dhal

ratio (w/w)

Fermentation

time (h)

TPA

parameters

and L* values

Constraints

imposed

Predicted

values

Observed

values

3 : 1.575

14.00

Hardness Minimum 19.340 019.92 ± 01.03

0.8279

Adhesiveness Minimum -0.030 -0.032 ± 00.01

Springiness Maximum 0.947 0.930 ± 00.14

Cohesiveness Minimum 0.773 000.78 ± 00.02

Chewiness Minimum 1299.7 1286.8 ± 32.20

Resilience Maximum 0.555 0. 547 ± 00.030

L* (lightness) Maximum 75.16 075.21 ± 00.58

65

PROCESS OPTIMIZATION OF IDLI USING SENSORY

ATTRIBUTES

4.1 INTRODUCTION

Fermented foods are defined as foods that have been subjected to the action of selected

microorganisms by which a biochemically and organoleptically modified substrate is

produced, resulting in an acceptable product for human consumption (Tamang, 1998).

There are different types of fermented foods, in which a range of different substrates are

metabolized by a variety of microorganisms to yield products with unique and appealing

characteristics (Campbell-Platt, 1994). Fermented foods supply important nutrients,

particularly proteins and amino acids. People become familiar with particular fermented

foods produced in their part of the world, and many of these foods became an integral

part of the local diet (Caplice and Fitzgerald, 1999) and culture, and were regarded as

essential for human consumption and nutrition.

Idli is one such food, which is prepared from low cost staple crop, which helps to

improve health. Its composition includes rice and black gram. In the traditional idli batter,

fermentation takes place due to the microflora present in the raw materials and in the

environment leading to the several changes that has impact on digestibility and nutritional

value bringing about desirable changes (Soni and Sandhu, 1989). The example of idli

illustrates the opportunities of co- fermentation of cereals (rice) and leguminous seeds

(black gram) (Young and Pellet, 1994).

A large proportion of the world cereal production is processed by fermentation prior to

consumption. The enhancement of attractive flavour and texture and the improved shelf-

life and digestibility as a result of fermentation, are important reasons for fermenting

cereals before consumption (Nout, 2009). Characteristic variables such as water content,

i.e. before and after soaking or fermentation, duration and temperature affect the cereal

fermentation (Hammes and Ganzle, 1998). This sour and spongy type breakfast food

(idli) of India and Sri Lanka constitutes an important group of naturally fermented food

(Ramakrishnan, 1979).

66

Legume contains more of proteins than cereals (Geervani and Theophilus, 1981).

Changes in the nutritive value of proteins as a result of fermentation are particularly

important for cereals and legumes. These sources of protein often are of lower nutritional

quality than animal products, and they tend to be major dietary sources of protein for

people with marginal and sub-marginal protein intake. Therefore, fermentation processes

that consistently improve protein quality or availability of cereal or legumes could have a

positive impact on the diets of people (McFeeters, 1988).

Cereal and legume being the important component of idli, the present study is done to

find out the interrelationship between the substrates during fermentation at different

fermentation time and different ratios of the substrates on the sensory attributes of idli

including desirable and non-desirable parameters with the objectives to select the

ingredients for optimum desirable product characteristics and to identify the optimum

levels of ingredients and fermentation time with respect to sensory attributes using

Response Surface Methodology (RSM).


4.2.1 Materials

In the current study, the most commonly used local variety of rice namely IR 20idli rice

and a protein rich black gram variety Aduthurai 3 (ADT3) which were chosen from the

preliminary study were used.

4.2.2 Preparation of Idli

Before framing the design using CCRD, preliminary trails were conducted to choose the

best suited rice, variation of black gram and ratios of rice and black gram dhal. The

varieties of rice chosen were parboiled rice, raw rice, ration rice, broken rice and red rice.

The variations in black gram dhal were black gram with husk, husk removed and husk

removed after soaking. The different ratios of rice to black gram dhal used were 3:1,

3:1.5, 3:2, 3:2.5, 3:3 and 4:1 respectively. The difference in batter volume after

fermentation and the texture of idli based on sensory was used to screen the ingredients

and ratios. The result of the preliminary study is discussed to show the reason for

choosing the maximum and minimum values for the independent variables chosen to

67

frame the model. The rice and black gram dhal were mixed at different ratios as per the

CCRD. To carry out the experiment framed using CCRD, the rice and black gram dhal

were soaked for 4 h and ground separately to a coarse consistency and mixed together.

The batter was left overnight (time based on the developed design) for fermentation with

addition of salt. The fermented batter was mixed thoroughly to expel the gas formed due

to the release of carbon-dioxide. The batter was poured in idli mould, and steamed in the

idli steamer for 15 minutes. The cooked idlis were subjected to sensory analysis.

4.2.3 Experimental design

4.2.3.1 Response Surface Methodology

A response surface methodology as explained by Box and Wilson (1951) was conducted

to determine the relative contributions of two predictor variables (ratio of rice to black

gram dhal and fermentation time) to the quality of the idli. RSM is an effective tool for

optimizing complex processes and has been widely applied in the food industry (Wong et

al, 2003; Lee et al, 2006; Sin et al, 2006). A CCRD was constructed using software

package Statistica (1999). Maximum and minimum predictor values were chosen after

carrying out preliminary cooking trails. Five levels of each predictor variable were

incorporated into the design. Table 4.1 shows levels of predictor variables. RSM reduces

the number of experiment trials needed to evaluate multiple parameters and their

interactions. For idli preparation different ratios of rice to black gram dhal and

fermentation time can be optimized using RSM keeping temperature constant (30o C).

4.2.3.2 Optimization of idli using RSM

The procedure was based on the hypothesis that quality attributes (desirable and

undesirable parameters) of idli were functionally related to ratios of rice to black gram

dhal and fermentation time, and attempts were made to fit multiple regression equations

describing the responses. Two coded independent variables in the process were rice to

black gram dhal ratio (X1) and fermentation time (X2). Five levels of each of the

independent variable were chosen for the study; thus, there were 15 combinations,

including the replicates of the centre point that were performed in random order, based on

an experimental CCRD for two factors as shown in Table 3.1 (Chapter 3).

68

4.2.3.3 Sensory analysis of idli

Idli samples were coded and served to ten panel members for analysis. The desirable

parameters included were colour, fluffiness, sponginess and fermented aroma. The

undesirable parameters included were compactness, firmness, stickiness and sourness.

The score card also had an option to give the score for overall quality of the sample. The

attributes selected were shown in Table 3. The panelists evaluated three sets of samples

at separate time. The first set included samples made with ratios 3:0.5 and 3:0.72 of rice

and black gram dhal respectively, the second set included samples made with ratio

3:1.25 and the third set included samples made with ratios of 3:1.78 and 3:2 with the

respective fermentation time as shown in Table 3.1. In each set 3 samples of idli were

placed for evaluation. The panel members were given a fifteen point rating scale to

evaluate the idli. The ranges of the quality of idli were given by panelist by marking a

line on the rating scale. The marking in the rating scale was counted as the score by using

a measurement scale.

4.2.3.4 Quantitative Descriptive Analysis (QDA)

The principle of QDA is based on the ability to train panelists to measure specific

attributes of a product in a reproducible manner to yield a comprehensive quantitative

product description amenable to statistical analysis (Ghosh and Chattopadhyay, 2011).

The panel members were selected and trained as how to evaluate the sample based on the

desirable and undesirable parameters for idli. PCA of the fermented food sample was

performed with the data collected from the panelists after scoring through 150 mm

unstructured scale. The descriptive sensory attributes are shown in Table 4.1.

4.2.4 Statistical analysis of data

The fitness of good was found through R2 or coefficient of determination (Haber and

Runyon 1977). All experimental designs and statistical data were analyzed and response

surface graphs, ANOVA, regression analysis were reported using Statistica (StatSoft,

OK, USA) software.

69

Table 4.1

Sensory attributes used for sensory analysis of Idli

Sensory attribute Description Range

Color

The colour of the idli range from pale yellow

to white

Low to high

Appearance Fluffiness

Compactness

The extent of fluffy appearance after cooking

the batter

The lack of porous nature in the idli

Low to high

Low to high

Texture

Sponginess

Firmness

Stickiness

The soft feeling obtained by the panelist while

touching the idli

The rigid nature of idli experienced by the

panelist by touch or bite

The adhesiveness of the idli experienced on

touch

Low to high

Low to high

Low to high

Aroma

Fermented

The characteristic aroma after the fermentation

of rice and dhal

Low to high

Taste

Sour

The range showing the extent of fermentation

on tasting

Low to high

Overall quality The impact of the product based on other

sensory attributes expressed by the panelist

revealing the acceptability of the product

Low to high

4.2.4.1 Principal Component Analysis (PCA)

Principal component analysis (PCA) is a statistical technique that can be applied to QDA

data to reduce the set of dependent variables (i.e., attributes) to a smaller set of

underlying variables (called factors) based on patterns of correlation among the original

variables (Lawless and Heymann, 1998).

70


The results are discussed under the following heads: 4.3.1 Desirable parameters of idli

4.3.2 Negative drivers of liking

4.3.3 Overall quality of the idli


4.3.1 Desirable parameters of Idli

The desirable and undesirable parameters of idli were evaluated by sensory analysis

because the evaluation of different cooked varieties of idli revealed the wide acceptance

of the conventional product due to its attractive aroma, taste and consistency (Soni and

Sandhu, 1989). The sensory parameters as shown in Table 4.1 were studied for the idli

made from the parboiled rice and black gram dhal with husk removed after soaking with

the ratios framed using CCRD at varying fermentation time. The idli showed large

difference in the sensory parameters in relation to the ratios and timing of fermentation

which is supported by the study done by Ghosh and Chattopadhyay (2011) who reported

that the changes during fermentation affect the physical properties like appearance,

texture, aroma, flavour and overall acceptability and these parameters are vital to assess

the acceptability of the product in the consumer point of view. Table 4.2 shows the score

given by panel members for desirable parameters. Table 4.4 shows the regression co-

efficient values for the desirable parameters. The R2

values

for colour, fluffiness,

sponginess were 0.953, 0.915 and 0.806 respectively which reaches unity favouring the

product.

4.3.1.1 Colour

The colour of the idli varied with the difference in ratios of the ingredients and change in

fermentation time. There was improvement in the colour of idli with increase in

fermentation time. As the ratio of black gram dhal increased there was gradual decrease

in brightness of idli colour due to the black gram dhal content. The R2 value (Table 4.4)

for colour was found to be 0.953. Fig.4.1.a to Fig 4.1.d shows the response surface graphs

for desirable parameters.

71

Table 4.2

Experimental designs and mean scores of desirable sensory attributes

* Centre point repeated 3 times

4.3.1.2 Fluffiness and sponginess of idli

Texture of idli is very critical from consumer point of view, it should be spongy, soft and

fluffy (Ramakrishnan 1979, Radhakrishnamurthy et al., 1961and Desikachar et al.,

1960). The texture of idli is influenced by many variables like raw material, quantity,

soaking time, grinding conditions, fermentation temperature and time and adjuncts on

quality of idli (Desikachar et al., (1960); Radhakrishnamurthy et al., (1961). The

fluffiness and sponginess increased with increase in the ratio of black gram dhal and

fermentation time. The maximum score for fluffiness

Sensory attributes

Overall quality Experimental

design points

Colour Fluffiness Sponginess Fermented

aroma

1 8.7±0.22 08.2±0.26 09.7±0.47 10.2±0.69 09.2±0.34

2 9.2±0.14 07.4±0.38 10.6±0.43 11.1±0.62 08.7±0.33

3 6.9±0.21 10.1±0.38 11.0±0.83 10.2±0.47 11.4±0.73

4 7.3±0.29 10.7±0.41 11.2±0.62 10.9±0.46 11.7±0.43

5 8.6±0.19 08.0±0.39 07.6±0.35 09.6±0.43 07.5±0.27

6 5.2±0.42 11.4±0.67 12.3±0.51 09.5±0.42 11.6±0.59

7 8.6±0.23 09.6±0.51 10.4±0.46 08.3±0.61 09.8±0.41

8 8.3±0.49 10.2±0.54 11.3±0.32 11.4±0.61 11.7±0.59

9 9.1±0.46 09.7±0.43 11.5±0.58 10.4±0.60 12.1±0.33

10* 8.8±0.44 10.2±0.64 11.4±0.51 10.7±0.47 11.9±0.49

72

Fig.4.1.a Response surface graph for colour

Fig.4.1.b Response surface graph for fluffiness

73

Fig.4.1.c Response surface graph for sponginess

Fig.4.1.d Response surface graph for fermented aroma

74

is 11.4 for the idli made of ratio 3:2 at 12 h fermentation time. The R2 value for fluffiness

was 0.915.

The important factor affecting the texture (sponginess, firmness and stickiness) of the

idli is the starch content of the ingredients which is supported by the study done by

Tharanathan and Mahadevamma (2003), that apart from its energy contribution, starch

content is the major factor which governs the texture of idli and as a result, to the

organoleptic properties of food. It was reported that the spongy texture of idli is also due

to the presence of surface active proteins (globulin) that generate a foamy character

resulting in the porous structure to the idli and this porous structure is stabilized even

during steaming process by the presence of viscogenic mucilaginous polysaccharide

called arabinogalactan (Susheelamma and Rao, 1979) proving that this viscosity and

foam stabilizing properties of native polysaccharide is a special functional value of foods

prepared from black gram (Tharanathan et al.,1994). As the starch content of IR20 rice is

79.5 per cent and that of black gram is 52 percent and the protein content of rice and dhal

were 6.46 and 24.16 respectively the texture of the developed idli is found to be good.

4.3.1.3 Fermented aroma

In case of fermented foods the shelf-life, texture, taste and aroma of the final product is

improved because of fermentation. The changes in fermentation depend on the available

nutrients in the starting materials, the unique metabolic abilities of the fermenting

microorganisms and possible interactions among all of these elements (McFeeters, 1987).

The response surface graph reveals that fermented aroma increased with increase in

fermentation time. Mukherjee et al., (1965), Rajalakshmi and Vanaja (1967) have

reported that black gram naturally possess L. mesenteroides, and the gas, acid and

several volatile compounds are formed during fermentation which contribute to a

complex blend of flavours in the products (Chavan and Kadam, 1989).

4.3.2 Negative drivers of liking

The compactness was high for the idli made with ratio 3:1.25, followed by 3:0.5 and

low for the idli made of ratio 3:2 (Table 4.3). This shows that the proportion of the

75

ingredients have a direct impact on the quality of the product. Fig.4.2.a shows that

compactness decreased with increase in fermentation time and with high quantity of

black gram dhal. The firmness (Fig.4.2.b) of the idli was high for the ratio 3:0.5 and it

was noted that firmness decreased with increase in black gram dhal quantity. The

undesirable parameter does not insist that the attributes are not required for the product

but should have moderate effect on the product. The attributes such as compactness,

firmness and stickiness when high are generally disliked by the consumers. Table 4.4

shows the regression co-efficient values for the undesirable parameters

Table 4.3

Experimental designs and mean scores of undesirable sensory attributes

* centre point repeated 3 times

Experimental

design points

Compactness Firmness Stickiness Sourness

1 8.7±0.57 9.2±0.47 11.3±0.46 8.5±0.40

2 8.5±0.46 9.6±0.53 11.1±0.50 9.6±0.58

3 9.2±0.58 5.8±0.42 9.8±0.44 8.9±0.45

4 8.1±0.55 6.2±0.43 9.2±0.41 10.3±0.38

5 9.4±0.74 11.5±0.50 8.3±0.43 8.2±0.37

6 7.8±0.65 5.3±0.35 7.4±0.35 8.1±0.53

7 9.7±0.65 5.8±0.52 7.1±0.35 6.4±0.29

8 8.1±0.53 4.9±0.52 7.1±0.38 9.7±0.42

9 8.5±0.68 5.7±0.44 7.7±0.43 9.1±0.44

10* 8.7±0.51 5.4±0.53 7.4±0.35 9.3±0.49

76

Fig.4.2.a Response surface graph for compactness

Fig.4.2.b Response surface graph for firmness

77

Fig.4.2.c Response surface graph for stickiness

Fig.4.2.d Response surface graph for sourness

78

4.3.2.1 Stickiness of the idli

The physicochemical properties such as moisture content, adhesion and hardness are all

induced by the processing conditions which affect the textural as well as eating quality of

rice. The parboiling treatment given to rice decreases the stickiness (Roy et al., (2004),

Kato et al., (1983), Biswas et al., (1988) and Islam et al., (2001). Rice with low amylose

content is generally soft when cooked, whereas rice with high amylose content has higher

grain hardness (Juliano, 1971). High-amylose rice has more long chains than low-

amylose rice (Hizukuri et al., (1989) and Radhika et al., (1993). The more long chains,

the firmer the rice is when cooked and vice-versa (Bhattacharya, 2004). Rice with high

water binding capacity normally yields soft texture cooked rice (Mohapatra and Bal,

2006). In the present study the amylose content was low in the parboiled rice (32%) and

black gram dhal (17%) compared to the amylopectin content (Table 5.1) hence the

stickiness is due to the ratios of rice and black gram dhal and the fermentation time. An

optimum ratio and fermentation time can yield a product with low to minimum stickiness.

Fig 4.2.c shows the response graph for stickiness of idli.

4.3.2.2 Sourness of Idli

Fig.4.2.d show that sourness increased with increase in fermentation time. The sourness

was high (10.3) for the idli made of ratio 3:1.78 at 13.42 h fermentation time. Increase in

fermentation time increases the acidity of the batter due to microbial growth which leads

to increase in sourness of the batter. The R2 value for sourness was found to be 0.884.

79

Table 4.4

Regression co-efficient for sensory parameters

Independent

variables

Regression co-efficients

C

olo

ur

Flu

ffin

ess

Spongin

ess

Fer

men

ted

arom

a

Com

pac

tnes

s

Fir

mnes

s

Sti

ckin

ess

Sourn

ess

Mean/Interaction

-6.367

-2.919 -18.396 -6.970 16.848

27.570 36.448 -17.399

1. Rice : Dhal ratio

(L)

6.722

-0.551 10.968 3.152 3.359

-18.180 -15.245 0.959

Rice : Dhal

ratio (Q)

-3.332*

-1.068 -2.465 -0.974 -0.112

5.804 5.762 -0.77

2. Fermentation

time (L)

2.019

1.899 3.4125 2.072 -1.357

-1.353 -2.905 3.677

Fermentation

time (Q)

-0.081

-0.101 -0.121 -0.061 0.059

0.055 0.125 -0.132

1L by 2L

-0.033

0.465 -0.233 -0.066 -0.299

0.000 -0.132 0.099

R2

0.953

0.915 0.806 0.646 0.941

0.948 0.853 0.884

L = linear effect; Q = quadratic effect; *= p < 0.005

Table 4.5

Regression co-efficient for overall quality of idli

Independent variables Regression co-efficients

Mean/Interaction -39.697

1. Rice : Dhal ratio (L) 10.062

Rice : Dhal ratio (Q) -4.263*

2. Fermentation time (L) 7.0723

Fermentation time (Q) -0.299

1L by 2L 0.266

R2 0.952

L = linear effect; Q = quadratic effect; *= p < 0.005

80

4.3.3 Overall quality of the idli

Table 4.4 shows that the overall quality of the idli in sensory attribute was high (12.1) for

the ratio 3:1.25 at 12 h fermentation time. Fig 4.3 illustrates the surface graph showing

the relation between ratios of rice and black gram dhal and fermentation time on the

overall quality of idli taking into consideration all sensory attributes of idli. From Table

4.5 it was known that the overall quality of the idli was at 5% level of significance with

the change in ratio of rice to dhal ratio in quadratic effect. The R2 value for overall

quality was 0.952.

Fig.4.3 Response surface graph showing the overall quality of the idli


Simultaneous optimization was performed for sensory attributes parameters like colour,

appearance, texture, taste, aroma and overall quality by imposing desirability constraints.

In case of sponginess, the softer idli shows high sponginess. Hence the software finally

gives a maximum desirable score and the condition at which the maximum score can be

81

obtained with some constraints by assigning maximal desirability score as 1 and minimal

desirability score as 0. Table 4.5 shows the constraints imposed for idli with better

sensory attributes with the desirable value for both independent and dependant variables.

The maximum desirable score that can be achieved with the desirable value will be

0.7439. On the basis of these calculations good idli could be made when the rice to black

gram dhal ratio is 3:1.475 (w/w), fermented for 10.2 h. The optimum results were

validated by performing the experiment at the optimized ratio and fermentation time by

comparing the observed and the predicted values. The predicted values are shown in

Table 4.5. The observed and predicted values were not significantly different (P >0.05)

which confirmed the optimization results.

Table 4.5

Simultaneous optimization of process parameters by desirability approach

4.3.5 Principal Component Analysis (PCA)

Sensory scores were subjected to PCA analysis. The PCA analysis revealed that PC1 and

PC2 accounted for 78 percent of the total variance in the data matrix. It is clear from the

plot that sensory attributes like sponginess and fluffiness associated with each other

Independent

parameters

Dependent variables

Overall

Desirability

score

Rice : dhal

ratio

(w/w)

Fermentation

time (h)

Sensory

parameters

Constraints

imposed

Predicted

values

Observed

values

3 : 1.475

10.2

Colour Maximum 08.00 08.20±0.64

0.7439

Fluffiness Maximum 09.81 09.60±0.72

Sponginess Maximum 11.01 10.70±1.42

Fermented aroma Optimum 09.35 08.70±0.30

Compactness Optimum 09.35 08.80±0.39

Firmness Minimum 05.26 05.60±0.42

Stickiness Optimum 07.87 08.10±0.32

Sourness Optimum 07.60 07.30±0.28

Overall Quality Maximum 10.89 10.60±0.51

82

strongly on the positive side of the PC1 axis while firmness, compactness, stickiness

were clustered together on the negative side of the PC1 axis. The third cluster is formed

by fermented aroma and sourness on the positive side of PC2 axis. Sample from the

experimental design point 6 was closely associated with desirable sensory attributes like

sponginess and fluffiness followed by sourness and fermented aroma. On the other hand,

design points 5, 1 and 2 were closely correlated with undesirable sensory attributes like

firmness, compactness and stickiness (Fig.4.4). From the PCA biplot it is clear that PCA

Fig.4.4 Principal Component Analysis (PCA) biplot of experimental design points

over sensory attributes of idli (refer Table 3.1 for design points)

is a powerful technique which can discriminate the samples and attributes within the data

matrix, depending upon their inter relationships.

4.3.6 Optimization of texture and sensory attributes

The optimization results indicated that the optimum ratio of rice to black gram dhal is

3:1.575 (w/w), with 14 h of fermentation time will provide the product with maximum

83

score for desirable textural parameters. On sensory analysis followed by RSM analysis of

idli prepared from various combinations of ingredients fermented at different durations

up to 14 h, the rice and dhal combination of 3:1.475 fermented to 10.2 h was found to be

the best accepted product. The results of both texture and sensory were combined to get

an optimized result which gave idli with the best instrumental texture quality as well as

sensory attributes. The impact making attributes of the idli chosen were shown in table

4.6. From the table it was found that the observed values and the predicted values showed

no significant difference (p > 0.05) and the model fits the design.

Table 4.6

Combined analysis of texture and sensory attributes

NS = No Significant difference, (p> 0.05)

3.4 CONCLUSION

On sensory analysis followed by RSM analysis of idli prepared from various

combinations of ingredients fermented at duration up to 14 h, rice and dhal combination

of 3:1.475 fermented to 10.2 h was found to be the best accepted product. On merging

TPA and sensory results (Chapter 3 and 4) an optimized ratio of 3:1.18 and fermentation

time of 12.02 h was evolved.

Independent

parameters

Dependent variables

Overall

Desirability

score

Rice:dhal

(w/w)

Fermentation

time (h)

Sensory /

Texture

Constraints

Imposed

Predicted

Values

Observed

values

3:1.18

12.02

Colour Maximum 10.11 10.60±0.36NS

0.714

Sponginess Maximum 11.70 11.31±0.67 NS

Stickiness Minimum 07.01 07.40±0.41 NS

Sourness Minimum 07.42 07.70±0.19 NS

Overall quality Maximum 12.14 11.85±0.86 NS

Hardness Minimum 25.15 24.83±1.07 NS

Springiness Springiness 0.892 00.91±0.06 NS

Resilience Maximum 0.641 00.62±0.03 NS

84

NUTRITIONAL COMPOSITION OF OPTIMIZED IDLI

5.1 INTRODUCTION

Adequate nutrition through food is necessary for human life. Essential micro and

macronutrients required for growth, metabolic regulations and physiological functions is

provided by foods. The World Health Organization (WHO) recognizes the importance of

breakfast in human diet. Nutritional value of idli has been reported in numerous

publications; however, there are few studies on optimized idli. In this study the

nutritional composition of optimized idli and its ingredients were studied without any

starter cultures. Total carbohydrates and fats were broken down by natural fermentation

process into oligosaccharides and fatty acids. Oligosaccharides have been known for its

prebiotic activity thereby it enhances the probiotic flora in the human gut.


5.2.1 Nutritional composition of the idli

Nutritional composition of the raw ingredients (idli rice - IR 20, black gram variety ADT

3) and optimized idli were determined. Nutrients like starch, amylose, total

carbohydrates, total sugars by Sadasivam and Manickam (2008), protein, fat and crude

fibre (Cunniff, 1995) were estimated.

5.2.2 Determination of fatty acids and alcohols

Fatty acids and alcohols were determined for the unfermented, fermented idli batter and

idli prepared after optimized fermentation time. One gram of the sample was weighed

and suspended into 10 ml of methylene chloride. The extraction of fatty acids and

alcohols was done using the method followed by Agrawal et al., (2000). The extracted

samples were analyzed for fatty acids and alcohols using Liquid Chromatography – Mass

Spectrophotometer (LC-MS) (Thermo Finnigan Surveyor and Thermo LCQ Deca XP

MAX). The experimental column used in LC-M was BDS HYPERSIL C18 and the

volume of sample injected was 10µL.

85

5.2.3 Determination of oligosaccharides

The determination of fatty acids and alcohols were done for the unfermented, fermented

idli batter and idli prepared after optimized fermentation time. The extraction of

oligosaccharides was performed as per Carlsson et al., (1992). The extracted samples

were analyzed using LC-MS (Thermo Finnigan Surveyor and Thermo LCQ Deca XP

MAX). The experimental column used in LC-MS was BDS HYPERSIL C18 and the

volume of sample injected was 10µL.


The results are discussed under the following heads:

5.4.1 Nutritional composition of idli

5.4.2 Fatty acids and alcohols in optimized idli

5.4.3 Disaccharides and oligosaccharides in optimized idli

5.3.1 Nutritional composition of idli

Proximate analysis of idli showed 81.60 g% total carbohydrates, in which starch was 75.0

g % (Amylose - 31.00, Amylopectin - 44.00). Protein content of rice and black gram were

6.46 g %, and 24.16, and optimized idli was found to be 10.21 g%. The fat and crude

fibre concentrations in optimized idli were 00.10 ± 0.01 and 00.28 ± 0.01 g% respectively

(Table 5.1). The carbohydrate level was comparatively high in optimized idli than

protein, fat and crude fibre.

Presence of amylose and amylopectin considerably influences rice starch digestion in the

gastrointestinal tract, influencing faecal excretion and constitution, postprandial blood

glucose response and total cholesterol. Amylose content is normally used to evaluate

some properties of product consumption such as cohesion and softness and also aid the

control of biologically relevant parameters such as blood glucose and triglyceride

concentration (Denardin et al, 2007). Amylose and amylopectin are fermented in the

gastro-intestinal tract by 72% of the human colonic bacteroid strains (Salyers et al,

1977a, b). This study shows that the amylose and amylopectin in idli will help in the

growth of gut microflora supporting the starch polysaccharide as a prebiotic. The good

86

amount of starch in idli is attributed by its raw ingredients. Starch were broken down to

form reducing sugars and oligosaccharides which led to reduction in starch content in idli

compared to the raw ingredients.

Table 5.1

Proximate composition of optimized idli

Parameters

(g % ± SD)

Rice

(Variety IR 20)

Black gram

(Variety ADT3)

Idli

(3:1.18)

Starch 79.50 ± 2.90 52.00 ± 1.21 75.00 ± 2.84

Amylose 32.00 ± 1.60 17.00 ± 0.74 31.00 ± 1.42

Amylopectin 47.50 ± 2.37 35.00 ± 1.62 44.00 ± 2.08

Total carbohydrates 84.00 ± 3.52 65.80 ± 3.02 81.60 ± 3.42

Protein 06.46 ± 0.32 24.16 ± 1.20 10.21 ± 0.50

Fat 00.27 ± 0.13 00.87 ± 0.02 00.10 ± 0.01

Crude fibre 00.20 ± 0.01 00.70 ± 0.03 00.28 ± 0.01

The protein content of idli prepared from combination of different starter culture namely

Pediococcus pentosacens, Enterococcus faecium MTCC 5153, Ent. faecium IB2 with

Candida versatilis were 3.3, 3.2 and 3.2 respectively (Sridevi et al, 2010). In a study

done by Nazni and Shalini (2010) the protein content of the developed idli prepared from

pearl millet was found to be 9.16g and the corresponding standard idli had 7.0 g whereas

the protein content of the optimized idli in the current study was high (10.21 g %) which

is found to be nutritionally rich even without addition of starter culture or millets. The

major contribution of protein to the idli was attributed by the variety of black gram used

when compared to rice.

Decrease in fat content of idli was noted when compared to raw ingredients which may

be due to the degradation of fats into fatty acids during fermentation process by

microorganisms.

87

5.3.2 Fatty acids and alcohols in optimized idli

Fatty acids and alcohols were analyzed in unfermented batter (Fig.5.1), Fermented batter

(Fig.5.2), and idli (Fig.5.3) using LC-MS. Pentacontanoic acid, Hexadecanoic acid,

Pentadecanoic acid, Nonadecanoic acid, Hexacosane, Nonacosane, Nonacosanol, 9-

Decanal, Decyl decanoate were present in unfermented batter, in which Relative

Abundance (RA) of Pentacontanoic acid was maximum (38 %). In fermented batter

Pentacontanoic acid, Decanoic acid, Octadecanoic acid, Hexadecanoic acid,

Pentadecanoic acid, Nonadecanoic acid, Hexacosane, Nonacosane, Nonacosanol, 9-

Decanal, Decyl decanoate, Propanol and 2-Pentanone were present. Fatty acids and

alcohol profile of idli was similar to fermented batter but Pentadecanoic acid and

Nonacosanol were absent in final idli. The relative abundance (RA) of Fatty acids and

alcohols in unfermented batter, fermented batter and idli is given in Table 5.2.

Table 5.2

List of fatty acids and alcohols

Unfermented batter Fermented batter Idli

Acids RA

(%)

Acids RA

(%)

Acids RA

(%)

Pentacontanoic acid 38 Pentacontanoic acid 23 - -

- - Decanoic acid 12 Decanoic acid 58

- - Octadecanoic acid 10 Octadecanoic acid 20

Hexadecanoic acid 11 Hexadecanoic acid 100 Hexadecanoic acid 100

Pentadecanoic acid 21 Pentadecanoic acid 8 Pentadecanoic acid -

Nonadecanoic acid 19 Nonadecanoic acid 19 Nonadecanoic acid 19

Hexacosane 11 Hexacosane 11 Hexacosane 10

Nonacosane 12 Nonacosane 19 Nonacosane 19

Nonacosanol 18 Nonacosanol 26 - -

9-Decanal 6 9-Decanal 8 9-Decanal 12

Decyl decanoate 8 Decyl decanoate 20 Decyl decanoate 20

- - Propanol 10 Propanol 10

- - 2-Pentanone 10 2-Pentanone 10

88

Fig. 5.1 Typical chromatogram and mass spectra showing fatty acids in

unfermented batter

89

Fig. 5.2 Typical chromatogram and mass spectra showing fatty acids and alcohols in

fermented batter

90

Fig. 5.3 Typical chromatogram and mass spectra showing fatty acids in optimized

idli

Mahadevappa and Raina (1978), reported that among the five varieties of legumes

namely cow pea, field gram, red gram, horse gram and black gram, the major saturated

fatty acid was palmitic acid which constitutes 15-25% in the neutral lipids, 20-40%

in the glycolipids, and 26-30% in the phospholipids. It was also found that in the

91

two black gram (P. mungo T9 and Khargan 3) varieties, the fatty acid profile is

characterized by exceptionally high levels of linolenic acid in all lipid classes: 60%

in the neutral lipids, 50% in the glycolipids, and 33% in the phospholipids,

accompanied in all categories by about 10% of linoleic acid and 15-20% of oleic acid.

High levels of the two unsaturated essential fatty acids could have nutritional

implications. In the present study, Hexadecanoic acid which is known as palmitic acid

was found to be 100% in relative abundance in idli when compared to unfermented

batter. Octadecanoic acid which is called as stearic acid was absent in unfermented batter

but appear after fermentation in fermented batter and as well with a relative abundance of

10 – 20 %. Stearic acid is a long chain fatty acid consisting of 18 carbon atoms without

double bonds. Ahrens et al. (1957), Keys et al., (1965), Hegsted et al. (1965 and 1993),

and Yu et al (1995) found that saturated fatty acids with chain lengths more than 10

carbon atoms generally raised blood cholesterol levels whereas polyunsaturated fatty

acids – PUFA (primarily linoleic acid) lowered blood cholesterol levels; and

monounsaturated fatty acids had either a neutral or mildly hypo-cholesterolemic effect on

blood cholesterol levels. These investigators also found that the stearic acid, a saturated

fatty acid did not increase blood total or low density lipoprotein (LDL) cholesterol levels

(bad cholesterol). Study by Yu et al. (1995), reported that adults were fed controlled,

whole-food diets, to evaluate the effect of stearic acid on blood lipid levels revealed that

stearic acid, showed no effect on LDL, and high density lipoprotein (HDL). A meta-

analysis done by Mensink (2003) consisting of 35 controlled trials showed that when

stearic acid replaced carbohydrate in the diet it had a neutral effect on blood lipid and

lipoprotein levels.

In foods like chocolate and lean red meats it was reported that their in-take does not

increase the risk of cardiovascular disease because of high levels of stearic acid part in

their saturated fatty acid. Similarly lean red meat (beef) and lean white meat (chicken,

fish) are equally effective in reducing total and LDL cholesterol in adults fed lipid-

lowering diets (Ding et al., 2006, Davidson et al., 1999, Hunninghake et al., 2000, Scott

et al., 1994 and Melanson et al., 2003) may be attributed in part to red meat‘s higher

content of stearic acid compared to that in chicken or fish. The flavour characteristic

known to be prevalent in idli batter appear from the combination of raw materials (rice

92

and black gram) and microbial starter cultures (natural inoculum) which helps in

fermentation. Buttery et al., (1988) reported that ketones composed of ethanone,

pentanone and butanones are found in rice. In the present study as the fermentation

begins, it leads to the formation of 2-pentanone which is found to appear in fermented

batter and not in unfermented batter. Polyunsaturated fatty acids play a primary role in

the development of ketones and this source has been attributed to black gram dhal

(Steinkraus et al. 1967). Microorganisms during fermentation lead to acidification of the

raw material producing organic acids, mainly lactic acid. Also, their production of acetic

acid, ethanol, aroma compounds, bacteriocin, exopolysaccharides and several enzymes

improve shelf life, microbial safety, texture, and play a role increasing the pleasant

sensory profile of the end product (Leroy and De Vuyst 2004). This finding supports the

current study that the fermentation of idli batter helped in the formation of acetic acid,

Dodecanol, Propanol and phenyl ethyl alcohol that improved the texture and sensory

profile of the optimized idli.

5.4.3 Disaccharides and oligosaccharides in optimized idli

Table 5.3 shows the list of disaccharides and oligosaccharides present in unfermented

batter, fermented batter and in idli. Trehalose, maltose, melezitose, maltotriose,

maltotetrose, maltopentose and maltohexose that were absent in unfermented batter

appeared in fermented batter and idli which is due to the breakdown of polysaccharides

into oligosaccharides and disaccharides during the process of fermentation. Typical

chromatograms and mass spectra showing disaccharides and oligosaccharides for

unfermented batter (Fig.5.4), fermented batter (Fig.5.5) and idli (Fig.5.6) are shown

below.

Crittenden & Playne, (1996) proved in their study that oligosaccharides in doses of <15

g/day increase bifidobacteria numbers in the colon. Authors suggest that a daily intake of

10 g of galacto-oligosaccharides is sufficient to cause a bifidogenic effect. Seeds of

legumes, lentils, and mustard are rich source of raffinose oligosaccharides (Johansen et

al., 1996; Sánchez-Mata et al., 1998). Hate et al (1983) reported that clinical data of

Japanese researchers suggest a regular addition of fructooligosaccharides to diet lowers

93

total cholesterol and triglyceride in blood which is proved by Losada and Olleros (2002)

that fructooligosaccharides increase production of volatile fatty acids by the action of gut

microflora on oligosaccharides have effect on cholesterol in the liver.

Table 5.3

List of Disaccharides and Oligosaccharides

Compound Non-Fermented batter Fermented batter Idli

Saccharose + + +

Trehalose - + +

Maltose - + +

Melezitose - + +

Raffinose + + +

Maltotriose - + +

Stachyose + + +

Maltotetrose - + +

Verbascose + + +

Maltopentose - + +

Maltohexose - + -

Cereal grains consist of at least two types of oligosaccharides such as galactosyl

derivatives and fructosyl derivatives. Galactosyl derivatives include sucrose, stachyose

and raffinose and fructosyl derivatives include sucrose and fructo-oligosaccharides

(Henry and Saini, 1989). Table 5.3 shows that the presence of raffinose in unfermented,

fermented batter and idli was attributed by the raw ingredient black gram dhal. This

finding was supported by the Voragen (1998) who indicated that raffinose and stachyose

in soya bean and other pulses and leguminous seeds are examples of naturally occurring

non-digestible oligosaccharides.

94

Fig. 5.4 Typical chromatogram and mass spectra showing Disaccharides and

oligosaccharides in unfermented batter

95


oligosaccharides in fermented batter

96


oligosaccharides in optimized idli

97

Results showed that there was reduction in the abundance of disaccharides and

oligosaccharides namely saccharose, trehalose, melezitose, maltotriose, maltopentose and

raffinose in idli compared to fermented batter. Onigbinde and Akinyele (1983) also had

proposed that decrease in the levels of raffinose, stachyose, and verbascose during

cooking might be attributed to heat hydrolysis to disaccharides and monosaccharides or

to the formation of other compounds. Basha (1992) showed that the rate of

oligosaccharide breakdown increased with increasing acid concentration. This rope with

the current study which shows that steaming of fermented batter to get idli may decrease

the level of abundance of oligosaccharides in idli when compared to fermented batter.

The acidic medium is caused by the action of microorganisms during fermentation

process (Sridevi et al, 2010).

The isomers of trehalose showed an increase in bifidobacteria population similar to

fructooligosaccharides giving high prebiotic index in the in-vitro fermentation (Sanz et

al, 2005). Carbohydrates can also act as prebiotics for selected bacterial group within the

gut reducing the pathogen population by increasing immunity (Gibson, 1998). Presence

of disaccharides and oligosaccharides in idli will possibly help to improve the health by

improving the gut microflora.

5.4 CONCLUSION

The fatty acids namely Decanoic acid, Octadecanoic acid and Hexadecanoic acid were of

high relative abundance in idli compared to unfermented batter. Regarding the

oligosaccharide profile, the sugars namely trehalose, maltose, melezitose, maltotriose,

maltotetrose and maltopentose were formed during fermentation. The process of

fermentation has led to the increase in nutrient content of the idli.

98

IMPROVING THE SHELF LIFE OF READY TO COOK IDLI

BATTER

6.1 INTRODUCTION

Ready to cook idli batter which was optimized to give desired quality parameters in the

earlier chapters (3 and 4) could only be successfully commercialized as a viable product

only its shelf-life is increased substantially from approximately one day to at least several

days.Idli, unlike other ready to cook food products rapidly gets over fermented as it is a

live actively growing bacterial medium, although common spoilage problems are less.

This is a challenge in terms of its preservation and shelf life. Ready to cook idli batter is

already available in the market as a packaged product. For several years prepared by local

vendors as a perishable product sold on daily basis or stored and sold under refrigerated

conditions. For the first time we have hypothesized that modification of gaseous

environment in the packaged form could regulate the fermentation flora in the medium

leading to longer shelf life. Second part of the hypothesis is that regulating the gaseous

exchange with the external environment could support the modified atmosphere in the

packaged product to work long.

MAP helps to preserve foods by reducing microbial spoilage thereby increasing

storability. MAP is done to maintain the freshness of the produce when purchased.

Success of MAP packaged foods depends on the quality of raw material and hygienic

practices followed during preparation and packaging, the gas mixture used for packaging

and the packaging material. The gases used in MAP are CO2, O2 and N2. Researchers

have successfully applied MAP to perishable foods like fruits, vegetables, flesh foods and

certain dairy products.


6.2.1 Materials

1. Modified Atmosphere Packaging machine (VAC Star-Swiss)

2. Head space analyzer (Dansensor, Italy)

3. Gas mixer (Dansensor, Italy)

4. Packaging materials- LDPE, PP, HM

99

6.2.2 Methods

6.2.2.1 Preparation of batter

The selected IR20 idli rice and ADT3 variety black gram dhal were taken in the

optimized ratio of 3:1.18. The quantity required varied for each set of experiment.

Ingredients were soaked and ground and were immediately packaged in the packaging

materials Fig.6.1 shows the research design of this chapter.

6.2.2.2 Selection of packaging materials

Three packaging materials namely low density poly ethylene (LDPE), Poly propylene

(PP), High Molecular (HM) were used for packing the idli batter. The thickness of the

packaging materials is given in Table 6.1. Dimension of the packaging material was 6×10

inches. 100g of the batter was filled in each pack.

Table 6.1

Thickness of packaging materials

Packaging materials Thickness (mm)

LDPE 0.009

LDPE 0.012

LDPE 0.014

PP 0.003

PP 0.005

HM 0.002

HM 0.006

6.2.2.3 MAP of idli batter

MAP was done using Modified Atmosphere Packaging machine (VAC Star-Swiss). MAP

machine consists of three gas cylinders viz., oxygen, carbon dioxide and nitrogen, each of

which is connected to a gas mixer provided with a separate cylinder where the required

combination of gases can be set and stored temporarily in buffer tank. Gas analyzer is

another important component of the MAP machine which helps to check if the gas is

mixed in the expected combination and the same is used for determining gas in the head

100

space of the packaged sample as and when required. Plate 6.1 shows the MAP machine.

The batter in each packet was packaged with modified air of required combination.

6.2.3 Respiration dynamics of the idli batter

Respiration dynamics was carried out to find the percentage of oxygen utilized and

percentage of carbon dioxide released during fermentation of batter. Respirometer as

designed by Bosco (1997) was used. Plate 6.2 shows the picture of respiration dynamics

done for the idli batter using respirometer connected to gas analyzer. The respirometer

consists of a glass jar without spout of capacity 250 mL resting on a flat MS plate and

covered with another MS plate. Both the plates had hole at each corner through which

bolt were inserted. By tightening the nuts of these bolts, the glass jar could be closed with

the cover plate. The joint between the glass jar and the cover plate was made air tight by

providing a neoprene rubber gasket. The cover plate had one hole at the centre where the

gas septum had been fixed for sampling the gas. Gas tightness of Respirometer was

verified by the respirometer ability to hold 50 mm vacuum for 15 minutes as done by

Plate 6.1 Modified Atmosphere Packaging (MAP) machine

101

Brown (1922). For the experiment, 100g of fresh ground batter was taken in 250 ml

beaker. Atmospheric air was maintained inside the beaker. The Respirometer was

connected to the gas analyzer to monitor the change in gas environment every half an

hour. The experiment was conducted for 12.02h (optimized fermentation time).

Plate 6.2 Respirometer connected to gas analyzer

102

6.2.4 EXPERIMENT I

Experiment I was carried out to find suitable packaging material for idli batter. The study

was designed for 3 days (Sridevi et al., 2010), hence a total of 126 packets (7 packaging

materials × 6 gas treatments × 3 days) were required. Based on the optimized ratio, batter

was prepared. In each packaging material 100g of batter was packaged with gas treatment

of 0% CO2, 5% CO2, 10% CO2, 15% CO2 and vacuum packaging and sealed. The

package in which no treatment was done served as the control. The packaged batters were

stored in room temperature (30 C). Each day 42 packets representing 7 packaging

material and 5 gas treatments were analyzed for the gas mixture using gas analyzer.

6.2.5 EXPERIMENT II

In experiment II, the idli batter was packaged and sealed with 12 gas treatments and three

controls were used. Batter placed in vessel served as control I, batter packaged and sealed

with ordinary sealing machine served as control II, the batter packaged in packaging

material but not sealed served as control III. The gas treatments are shown in Table 6.2.

The study was done using selected 3 packaging material. Hence a total of 215 samples

were required. The MA packaged batter and control packs were stored in room

temperature (30 C). Each day 43 samples stored in three different packaging materials

with 12 gas treatments including 3 controls were analyzed for the gas concentrations (%)

followed by sensory analysis of the idli cooked from packaged batter. Overall quality

based on the colour, texture, fermented aroma of the idli was assessed.

103

Table 6.2

Gas treatment used in experiment II

Treatments CO2 (%) O2 (%) N2 (%)

1 00 15.0 85.0

2 05 15.0 80.0

3 10 15.0 75.0

4 15 15.0 70.0

5 00 17.5 82.5

6 05 17.5 77.5

7 10 17.5 72.5

8 15 17.5 67.5

9 00 20.0 80.0

10 05 20.0 75.0

11 10 20.0 70.0

12 15 20.0 65.0

13 Control I Batter in vessel

14 Control II Batter in unsealed package

15 Control III Batter packaged with ambient air

6.2.6 EXPERIMENT III

In experiment III, selected one packaging material and 8 gas treatments and control were

used. Gas treatments are shown in Table 6.3. In this experiment the batter packages were

left to check the extended shelf life of the batter.

Table 6.3

Gas treatment used in experiment III

Treatments CO2 (%) O2 (%) N2 (%)

1 0 15.0 85.0

2 0 12.5 87.5

3 0 10.0 90.0

4 0 07.5 92.5

5 5 15.0 80.0

6 5 12.5 82.5

7 5 10.0 85.0

8 5 07.5 87.5

104


6.3.1 Respiration dynamics

Respiration is usually the measure oxygen uptake or the production of CO2, producing

heat and water vapour. The results of respiration dynamics give an idea to flush the

package with required atmosphere so that steady state conditions are reached

immediately (Zagory and Kader, 1988). The O2 consumption and CO2 evolution differ

based on the composition such as fatty acids, sugars or organic acids of the respiring

sample (Dilley et al, 1990 and Platenius, 1942).

Fig.6.1 Change in gas concentration during its fermentation time

Fig.6.1 showed the O2% consumed and CO2 % evolved during the fermentation of idli

batter. As fermentation began, the O2% declined from 21% to 13.9%. The increase in

CO2% began after 2 h and gradually increased from 0% to 12.9%. The results showed

that 100g of idli batter consumed 7.1% O2 and produced 12.9% of carbon dioxide. Based

on the results of respiration dynamics MAP of ready to cook idli batter was done with

different gas treatments and the results are discussed below.

105

6.3.2 EXPERIMENT I

Table 6.4 shows the changes in atmosphere of the packaged idli batter. In treatment1

where the package was packed with lack of oxygen and carbon dioxide (0% O2 and 0%

CO2) showed a gradual increase in CO2 over three days of storage. This increase in CO2

is a result of fermentation of idli batter inside the package. The O2 (%) remained zero in

the LDPE packages but HM and PP showed increase in O2, which meant that the

packaging material permitted permeability of air. Fig.6.2 shows the changes in gas

mixture among different packaging material over three days of storage.

In treatment 2 where the package was flushed with 5% CO2, it was found that there was

increase in CO2 % from 5% to a maximum of 14.4 % CO2 in LDPE packaging material

during the second day of storage. In the packaging material PP (0.003mm) there was

decrease in CO2 to 0.8% on the third day. The O2 concentration in PP (0.003mm) and

HM (0.002 mm) were not maintained inside the package. Fig.6.3 shows the changes in

gas mixture among different packaging material over three days of storage.

In treatment 3 where the 10% CO2 was flushed in the package, LDPE of higher thickness

showed fermentation effect on the batter with increase in CO2, whereas in LDPE of lower

thickness, PP and HM the change in gas system was not gradual.

In treatment 4, the package was flushed with 15% CO2, increased in LDPE of medium

and lower thickness and the concentration of CO2 varied in other packaging materials

over the storage period. Fig.6.4 shows the changes in gas mixture among different

packaging materials.

Treatment 5 was vacuum packaging and over the storage period the gas concentrations

were not analyzed as the pressure was too low to detect the gas in the head space.

Treatment 6 was control with lack of gas treatments but package had ambient gas

composition. The atmospheric air in package favoured fermentation of batter which led to

decrease in O2 concentration.

From the results of experiment I it was inferred that gas permeability differed with

different packaging material. The O2 permeability was less than that of CO2 in LDPE of

varying thickness helped to maintain the atmosphere within the package compared to

other packaging materials. This result is supported by the study done by Bosco (1997),

106

who reported that, the O2 permeability of LDPE and PP was less than that of CO2 and the

variation in permeability of a film is due to the fact that the film were purchased from

the retail market at different places and might be from different batches of production

Table 6.4

Change in gas mixture over storage period

Packaging

material

Day 1 Day 2 Day 3

CO2 (%) O2 (%) CO2 (%) O2 (%) CO2 (%) O2 (%)

LDPE (0.14 mm)

Treatment 1 0.114 0 11 0 11.1 0.017

Treatment 2 5.6 0.009 6.3 1.07 10.9 0.009

Treatment 3 10.5 0.1 13.8 0 15.5 0

Treatment 4 14.2 0.008 12.4 0 8.9 19.4

Treatment 5 - - - - - -

Treatment 6 0 21 2.1 14.8 4.2 7.15

LDPE (0.12 mm)

Treatment 1 0.114 0 10.3 0 10 0.265

Treatment 2 5.6 0.009 10.6 5.4 10.8 5.2

Treatment 3 10.5 0.1 12.6 0 15.4 0.09

Treatment 4 14.2 0.008 14.9 0.011 14.9 0

Treatment 5 - - - - - -

Treatment 6 0 21 4.1 7.56 3.1 12.6

LDPE (0.009 mm)

Treatment 1 0.114 0 10.3 0 12.8 0

Treatment 2 5.6 0.009 14.4 0.484 15 1.2

Treatment 3 10.5 0.1 12.9 0 5.2 0.036

Treatment 4 14.2 0.008 10.5 0.095 12.6 0.015

Treatment 5 - - - - - -

Treatment 6 0 21 3.3 8.91 0.3 19.8

PP (Thin)

Treatment 1 0.114 0 9.9 0.112 12.7 0.112

Treatment 2 5.6 0.009 13.5 19.5 0.8 19.5

Treatment 3 10.5 0.1 11.3 19.1 1.2 19.1

Treatment 4 14.2 0.008 13.4 0.908 15.2 0.908

Treatment 5 - - - - - -

Treatment 6 0 21 0 20.3 0.3 19.8

107

PP (Thick)

Treatment 1 0.114 0 5.1 0.549 10.2 0.539

Treatment 2 5.6 0.009 10.8 0.001 15 0.001

Treatment 3 10.5 0.1 14.3 0.032 15 0

Treatment 4 14.2 0.008 15.2 0.001 14.6 0.149

Treatment 5 - - - - - -

Treatment 6 0 21 8.2 6.2 0 0.3

HM (Thin)

Treatment 1 0.114 0 3.4 3.18 11.6 9.5

Treatment 2 5.6 0.009 2.8 0.04 5.9 19.2

Treatment 3 10.5 0.1 0 20.4 0.8 18.9

Treatment 4 14.2 0.008 0.7 19.6 1 19.3

Treatment 5 - - - - - -

Treatment 6 0 21 0.4 19.5 0 20.3

HM (Thick)

Treatment 1 0.114 0 3.4 4 19.7 9.7

Treatment 2 5.6 0.009 6 0.5 7.3 0.6

Treatment 3 10.5 0.1 0.5 19.3 2.8 17.1

Treatment 4 14.2 0.008 0.1 20.3 4.1 9.39

Treatment 5 - - - - - -

Treatment 6 0 21 0.3 19.7 0.1 20.2

At low oxygen levels, anaerobic respiration can occur, resulting in production of

substances that contribute to off-flavours and odours (Lee et al, 1995 and Zagory 1995).

Hence the idli prepared from the batter were subjected to sensory analysis only for its

texture. Idli made from the batter packaged in different packaging material scored very

low rating which might be due to deterioration of the batter. The experiment was

repeated with combination of both O2 and CO2 in LDPE of varying thickness.

108

Fig. 6.2.a Treatment 1 (0% CO2) showing change in CO2 level (%) among different

packaging material

Fig. 6.2.b Treatment 1 (0% CO2) showing change in O2 level (%) among different

packaging material

109


packaging material


packaging material

110


packaging material


packaging material

111

6.3.3 Experiment II

Table 6.5 to 6.8 shows the changes in gas concentrations in the packaging materials with

idli batter. The 12 treatments showed the rate of fermentation of batter in different MAP

system in different packaging material at room temperature (30 C). Treatment 1 to 12

showed increase in concentration of CO2% within 48h of packaging which is due to the

evolution of CO2 during fermentation of the batter.

Treatment 1 showed gradual increase in fermentation rate of the batter for five days of

storage period compared to other treatments. The percentage of O2 decreased gradually

from 15% to 1.75% (LDPE 0.12mm). Fig.6.5 showed the changes in concentration of

CO2 and O2 among LDPE of varying thickness. The batter in treatments 5 to 12 which

were flushed with 17.5% to 20% O2 led to complete consumption of O2 in LDPE of 0.014

and 0.012mm by the batter supporting fermentation and also whey separation. During

storage of batter whey separation persisted (Nisha et al, 2005). The reason stated by

Nisha et al was that idli batter is foam in which gas molecules are entrapped in a solid-

liquid phase. The batter collapse and whey separates when the high energy interface takes

place during air-water interface. Fig.6.5 to 6.14 shows the depletion of O2 curve. LDPE

of 0.009mm did not support the MAP system showing variations in gas concentration

over the period of batter storage.

The gas combination was not analyzed for control I and II as they were exposed to the

atmospheric air. The O2 (%) concentration in control III was zero per cent and that of

CO2 decreased from 11% (2nd

day) to 5.7 % (5th

day) during storage. It showed that the

oxygen was consumed for the fermentation process and the carbon dioxide evolved was

decreased due to its permeability through the packaging material.

112

Table 6.5

Concentration of gases in LDPE (0.014mm) during the storage period

Treat-

ments

Gas combinations

Day 0 Day 1 Day 2 Day 3 Day 4 Day 5

CO2 (%) O2 (%) CO2 (%) O2 (%) CO2 (%) O2 (%) CO2 (%) O2 (%) CO2 (%) O2 (%) CO2 (%) O2 (%)

1 00 15.0 08.1 9.40 10.4 02.2 00 0.00 6.2 1.500 6.2 0.000

2 05 15.0 07.0 7.31 03.3 13.6 6.8 0.44 5.9 0.453 6.2 7.000

3 10 15.0 05.4 11.2 02.6 14.7 1.2 18.8 8.3 2.740 6.0 3.100

4 15 15.0 02.5 16.7 05.4 0.707 4.4 4.09 4.7 0.424 5.5 0.600

5 00 17.5 04.3 6.38 08.0 0.087 6.9 0.94 4.3 2.660 9.6 0.850

6 05 17.5 09.6 0.72 04.0 04.59 00 0.00 5.9 0.085 6.4 0.002

7 10 17.5 12.2 0.23 13.7 0.077 6.1 0.40 6.6 0.000 6.1 0.800

8 15 17.5 10.1 1.26 05.3 0.730 6.1 0.19 4.6 0.172 5.7 0.70

9 00 20.0 22.1 0.001 08.1 0.024 6.3 0.16 5.4 0.076 5.8 0.137

10 05 20.0 16.7 0.12 08.1 0.045 4.9 0.09 4.9 0.134 5.0 0.142

11 10 20.0 16.5 4.11 10.3 0.205 8.5 1.13 2.8 9.460 7.1 0.873

12 15 20.0 14.9 3.03 07.1 02.06 7.5 0.14 6.0 0.361 5.8 0.197

113

Table 6.6


Treat-

ments

Gas combinations



1 00 15.0 07.2 07.05 09.3 3.524 10.1 2.650 11.7 1.95 11.9 01.75

2 05 15.0 07.6 04.72 03.0 9.780 05.4 0.601 05.7 0.71 04.0 00.29

3 10 15.0 11.0 07.85 09.6 0.759 08.2 0.534 08.2 3.16 05.5 00.09

4 15 15.0 05.7 12.40 05.5 0.486 04.8 0.291 03.9 0.26 00.0 00.00

5 00 17.5 12.4 00.54 08.3 0.206 00.4 20.10 08.4 0.113 05.8 11.10

6 05 17.5 15.4 02.10 08.7 1.450 08.1 0.622 07.2 0.044 00.2 20.80

7 10 17.5 06.9 03.79 06.2 0.246 08.8 8.470 05.4 0.197 04.9 00.22

8 15 17.5 16.2 0.268 08.8 0.071 07.2 0.453 04.9 0.194 09.2 01.42

9 00 20.0 19.3 0.161 05.7 0.164 05.8 0.017 05.4 0.367 05.8 00.03

10 05 20.0 05.3 14.50 15.7 0.000 07.0 0.000 05.1 0.161 07.2 00.36

11 10 20.0 05.0 13.60 08.0 5.150 04.3 0.238 07.5 0.252 06.6 00.37

12 15 20.0 15.2 03.14 06.6 8.910 09.3 0.152 04.9 0.185 09.1 00.24

114

Table 6.7


Treat-

ments

Gas combinations



1 00 15.0 10.2 09.45 09.0 0.08 1.7 18.1 7.2 08.69 05.6 00.16

2 05 15.0 01.1 18.90 08.9 2.54 4.9 0.12 8.9 00.79 09.3 00.12

3 10 15.0 08.3 05.49 04.0 1.87 6.0 6.61 4.8 00.34 07.7 00.09

4 15 15.0 16.5 00.43 05.4 9.69 0.2 20.5 9.3 03.35 04.6 014.3

5 00 17.5 17.3 00.24 09.3 0.16 1.0 20.2 5.4 00.20 06.6 00.29

6 05 17.5 18.7 00.31 06.2 0.42 7.8 1.21 2.4 18.40 08.5 01.79

7 10 17.5 07.8 05.29 04.5 1.96 8.9 1.03 5.4 11.90 06.1 06.20

8 15 17.5 13.5 00.69 08.9 0.06 5.3 11.3 14 01.61 10.0 00.39

9 00 20.0 10.9 01.26 11.3 0.91 4.6 0.19 10.8 00.04 05.7 00.09

10 05 20.0 11.2 06.71 12.5 1.22 5.9 0.17 7.3 00.52 10.5 01.65

11 10 20.0 17.9 00.12 09.5 0.29 10.4 0.65 8.0 00.04 04.4 13.20

12 15 20.0 10.0 00.27 05.4 0.77 3.8 2.37 11.2 02.19 07.7 00.09

115

Fig 6.5.a Treatment 1 (0% CO2 and 15% O2) showing percentage of CO2 (%)

Fig.6.5. b Treatment 1 (0% CO2 and 15% O2) showing percentage of O2 (%)

Storage period

Storage period

116

Fig 6.6.a Treatment 2 (5% CO2 and 15% O2) showing percentage of CO2 (%)

Fig 6.6.b Treatment 2 (5% CO2 and 15% O2) showing percentage of O2 (%)

Storage period

Storage period

117

Fig. 6.7.a Treatment 3 (10% CO2 and 15% O2) showing percentage of CO2 (%)

Fig. 6.7.b Treatment 3 (10% CO2 and 15% O2) showing percentage of O2 (%)

Storage period

Storage period

118



Storage period

Storage period

119

Fig. 6.9.a Treatment 5 (0% CO2 and 17.5% O2) showing percentage of C O2 (%)

Fig. 6.9.b Treatment 5 (0% CO2 and 17.5% O2) showing percentage of O2 (%)

Storage period

Storage period

120

Fig. 6.10.a Treatment 8 (15% CO2 and 17.5% O2) showing percentage of CO2 (%)

Fig. 6.10.b Treatment 8 (15% CO2 and 17.5% O2) showing percentage of O2 (%)

Storage period

Storage period

121



Storage period

Storage period

122



Storage period

Storage period

123



Storage period

Storage period

124



Storage period

Storage period

125

Table 6.8


(0.014mm)

Treatments Sensory scores

Day 1 Day 2 Day 3 Day 4 Day 5 1 8.1 9.1 7.1 1 1

2 7.5 8.5 5.1 5.1 5.2

3 5.2 8.5 1 1 1

4 9.3 8.3 1 1 5.4

5 8.5 7.3 7.2 7.7 1

6 8.5 7.7 6.2 7.0 1

7 8.1 5.7 1 1 1

8 6.4 7.2 1 1 1

9 8.8 7.7 6.1 1 1

10 8.3 8.2 7.3 7.1 3.5

11 8.1 8.0 4.3 1 3.7

12 8.0 8.0 7.3 1 3.0

Control I 6.7 - - - -

Control II 8.0 5.2 - - -

Control III 8.2 7.4 - - -

Table 6.9


(0.012mm)


Day 1 Day 2 Day 3 Day 4 Day 5 1 3.0 7.3 8.2 8.3 9.0

2 4.0 7.1 5.4 5.6 5.0

3 6.2 7.4 7.9 6.9 6.2

4 6.3 7.2 6.4 6.8 5.1

5 6.1 6.5 5.2 6.8 5.7

6 6.3 8.3 8.9 8.5 7.3

7 8.2 8.5 6.8 6.4 5.1

8 6.3 7.2 7.7 5.9 6.3

9 8.2 6.3 6.4 5.2 6.2

10 8.5 7.3 5.9 6.0 6.1

11 8.5 4.2 5.4 6.7 6.6

12 8.2 6.0 4.0 5.2 5.3

Control I 6.8 - - - -

Control II 7.4 4.7 - - -


Table 6.10

126

Sensory scores of the product made from batter packaged in LDPE (0.009mm)


Day 1 Day 2 Day 3 Day 4 Day 5 1 7.5 6.4 1.5 1.6 3.8

2 8.1 5.3 1.5 1.8 3.7

3 5.4 5.9 1.7 1.9 2.7

4 8.2 4.5 1.3 1.4 4.3

5 8.0 6.1 1.4 1.7 2.7

6 8.3 6.2 4.0 1.6 1.6

7 8.5 6.3 6.2 1.5 2.7

8 8.2 8.1 1.7 1.8 1.8

9 5.3 8.3 6.5 5.2 3.2

10 7.8 7.4 5.7 4.3 2.9

11 5.2 8.1 5.3 2.5 3.2

12 5.0 6.3 5.2 2.0 1.6

Control I 6.8 - - - -

Control II 7.3 5.0 - - -


Table 6.8 to 6.10 showed the sensory scores of idli made from batter treated with

different gas combinations in different packaging material. The sensory score represented

the overall quality of the idli. Sensory scores of idli prepared on the second day of storage

showed high acceptability which might be due to the reason that the batter had been

fermented and gave idli of high acceptability. The scores ranged from 4.2 to 9.1

(treatment 11 in LDPE -0.012 mm and treatment 1 in LDPE- 0.014 mm). The sensory

scores on the third, fourth and fifth day showed poor acceptability of the product except

for treatments in LDPE 0.012 which increased during the storage period. The highest

score obtained was 9 for treatment 1 (Fig.6.15) followed by 7.3 for treatment 6 (Fig.6.16)

on the fifth day of storage.

The batter in control I was discarded due to over fermentation after 24 h followed by

fungal contamination. The batter in control samples were evaluated for sensory for a

maximum two days whereas the batter in packages was used for idli preparation and

evaluated for sensory on all storage days in spite of its poor scores. Thou there was whey

separation which made idli harder, the packaged batter used for idli preparation when

compared to control.

127

The results of experiment II discussed from gas concentration in different treatments and

different packaging material showed that LDPE of medium thickness (0.012 mm) may

support to maintain the MAP system inside the packaged atmosphere when compared to

LDPE of other thickness . The gas treatment of 0% CO2 with 15% O2 and 5% CO2 with

15% O2 were found to extend the shelf-life of the batter compared to other gas treated

samples and control samples.

Fig. 6.15 Comparison of sensory scores of idli made from

treatment 1 (0% CO2 and 15% O2)

128

Fig. 6.16 Comparison of sensory scores of idli made from

treatment 6 (5% CO2 and 15% O2)

6.3.4 Experiment III

The observations of experiment III are shown in Table 6.11. It was found that the

percentage of carbon dioxide increased in all treatments except for 8 which showed very

low CO2% and low O2%. The consumption of O2 percentage was high showing complete

decrease of O2 percentage in the package. During fermentation of batter oxygen is

consumed and when the fall is below 1% may lead to anaerobic respiration (Lee et al,

1995 and Zagory 1995). In the table 6.11, on the seventh day of storage, all treatments

showed poor concentrations of O2% except treatment 1 which showed 1.4% O2. Initial

pH of the fresh batter 6.41 and change in pH of the batter in different treatments over

seven days of storage showed decrease in pH. The change in pH is associated with the

development of Streptococcus faecalis producing both lactic acid, which lowers the pH

and carbon dioxide which leavens the batter (Balasubramanian and Viswanathan, 2007a).

The control sample was discarded on the third day due to fungal contamination.

129

Table 6.11

Comparison of gas mixture on the first day and seventh day of storage

Treatments Day 0 Day 7 CO2 (%) O2 (%) pH CO2 (%) O2 (%) pH

1 0 15.0 6.41 11.3 1.4 4.32

2 0 12.5 6.41 12.6 0.4 4.10

3 0 10.0 6.41 10.3 0.7 4.31

4 0 07.5 6.41 12.4 0.9 4.31

5 5 15.0 6.41 12.9 0.0 4.28

6 5 12.5 6.41 14.6 0.5 4.00

7 5 10.0 6.41 13.1 0.6 4.10

8 5 07.5 6.41 3.4 0.0 4.22

Control Ambient atmosphere 6.41 - - -

Table 6.12

TPA parameters of idli made from MAP batter

Treatments Hardness (N) Adhesiveness (N s) Springiness Cohesiveness Chewiness Resilience

1 17.020±4.68 -07.257±5.58 0.874±0.07 0.671±0.02 1024.01±333.8 0.386±0.02

2 21.455±1.22 -09.924±5.52 0.814±0.05 0.622±0.04 1106.65±95.3 0.337±0.04

3 21.705±2.72 -09.907±3.39 0.829±0.02 0.645±0.00 1181.11±116.7 0.364±0.02

4 19.500±2.63 -15.461±13.27 0.852±0.11 0.663±0.09 1112.96±155.5S 0.369±0.06

5 27.315±2.55 -10.757±05.48 0.870±0.01 0.686±0.07 1045.67±35.7 0.383±0.03

6 28.955±0.45 -12.552±02.95 0.843±0.04 0.624±0.05 1229.40±131.8 0.356±0.05

7 28.571±0.21 -09.417±06.58 0.858±0.05 0.666±0.03 1339.51±34.7 0.377±0.03

8 27.152±0.52 -14.790±00.09 0.904±0.06 0.720±0.00 1761.41±9.2 0.336±0.01

Control - - - - - -

The texture of idli prepared from the treated batter was analyzed and Table 6.12 shows

the TPA values of the idli. The hardness of the idli ranged between a minimum of 17.02

N (treatment 1) to a maximum hardness of 28.95 N (treatment 6). The hardness of idli

was low for the treatments 1 to 4 when compared to other treatments which were due to

the whey separation seen in treatment 5 to 8. The maximum springiness was found for the

idli made from the treatment 8 followed by idli made from treatment 1 and 5.

130

Cohesiveness was maximum for the idli made from the treatment 8 followed by 2 and 6.

Resilience was maximum for the idli made of treatment 1 (0.386) followed by treatment

7 (0.377). The texture profile values when compared with the optimized value show that

idli made from treatments 1 to 4 were soft compared to idli made from other treatments.

Table 6.13

Overall quality of idli

Treatments CO2 (%) O2 (%)

Overall quality

1

0

15

8.6 ± 0.84

2

0

12.5

7.0 ± 0.00

3

0

10

7.0 ± 1.34

4

0

7.5

7.4 ± 2.4

5

5

15

5.8 ± 0.49

6

5

12.5

6.4 ± 0.49

7

5

10

6.6 ± 0.70

8

5

7.5

4.0 ± 5.65

Control

Batter packaged with

ambient air

-

Table 6.13 shows the scores of overall quality of the idli made from MAP treated batter.

The maximum score was 8.6 (Treatment 1) followed by 7.4 (Treatment 4). The overall

comparison of the sensory scores show that treatments 1 (8.6), 2 (7.0) and 4 (7.4) had

high scores respectively when compared to treatments 5 to 8. Studies done by Day

(1996) and Zagory and Kader, (1988) showed that by modifying the atmospheric oxygen

level, particularly by lowering the oxygen concentration inside the package, the

respiration rate of the packaged produce is slowed down and the sensory shelf life can be

extended which cannot be applied to the current study. Idli batter being a live product

which produces 12.9% of CO2 during fermentation requires oxygen in order to maintain

aerobic condition and to sustain the aroma of the fermented batter and the final product

when the batter is steamed. Hence the study done by Song et al., (1998) Mattheis and

131

Fellman, (2000) supports the current study who reported that production of aromatic

compounds of many fruit, including apple, banana, pear, peaches, strawberries and

others, can be adversely affected by low O2 and elevated CO2 i.e., synthesis of aroma

compounds are generally suppressed. As mentioned in chapter 4, fermented aroma is one

the criteria of idli which will be considered for sensory analysis and hence the treatment

with high O2% may support the sensory quality of MAP packaged idli. The result of table

6.13 show that idli made from batter packaged with 0% to 5% CO2 and O2 ranging from

7.5% to 15% gave better results compared to all other treatments applied in the above

experiments.

6.4 CONCLUSION

From this study it can be concluded that ready to cook idli batter packaged in medium

thickness (0.012 mm) LDPE flushed with 0% CO2 and 7.5 to 15% O2 could increase the

shelf-life up to seven fold increase without compromising the sensory qualities at room

temperature.

132

EXECUTIVE SUMMARY AND CONCLUSION

Major objective of this work was to extend the shelf life of ready to cook idli batter using

modified atmosphere packaging and the sub-objectives were

1. To understand the presently followed practices for the preparation of idli.

2. To optimize the process of preparation of the product with respect to

ingredient ratios and fermentation time.

3. To improve the shelf-life of ready to cook idli batter by optimized process.

First chapter was conceptualized with an objective to understand the presently followed

practices for the preparation of idli. A survey based study was conducted in eight regions

through an oral interview scheduled which covered a sample size of 300. The results of

the survey indicated that at house hold level 68% of the selected population preferred

parboiled rice. Only 34 per cent used decorticated black gram whereas 49 per cent used

black gram with husk removed after soaking. Majority (99.7%) of the respondents used

3:1 ratio of rice and black gram dhal for preparing idli. Fermentation time varied between

5 h to 12 h at the selected households. Majority (71.3%) of them fermented the idli batter

for 11 to 12 h and 73% stored the idli batter in refrigerated condition. The results were

similar to the practices reported in literature such as variety of rice, type of black gram,

ratio of ingredients used for idli making, fermentation time and shelf –life of the batter.

Chapter 3 was aimed to optimize the process of preparation of the product with respect to

ingredient ratios and fermentation time based on the instrumental texture profile of the

idli using response surface methodology. Before framing the design using Central

Composite Rotatable Design, preliminary trails were conducted to choose the best suited

rice, variation of black gram and ratios of rice and black gram dhal. Five differently

processed rice and ADT3 variety dhal were used for the preliminary study. Results of the

preliminary study showed that IR20 parboiled rice and ADT3 variety black gram dhal

with husk removed after soaking were best suited for idli making. The rice and black

gram dhal were mixed at different ratios as per the CCRD. The independent parameters

for this study were ratios of rice to black gram dhal and fermentation time. The dependent

133

parameters were the texture attributes namely hardness, adhesiveness, springiness,

cohesiveness, chewiness and resilience.

The results obtained were subjected to regression analysis and ANOVA. Based on the

results certain constraints were imposed on the dependent parameters to get idli with

better texture properties and the predicted values were obtained for the dependent

parameters.

From the study it was concluded that the optimum ratio of rice to black gram dhal is

3:1.575 with an optimum fermentation time of 14 h where a desirable value of 0.8279

will be obtained for the product. The results were validated by preparing idli at the

optimized conditions. The results prove the designed model to be valid.

Chapter 4 focused on the objective to identify the optimum ratios of ingredients and

fermentation time with respect to sensory attributes using Response Surface Methodology

(RSM). The desirable sensory attributes were colour, fluffiness, sponginess and

fermented aroma. The undesirable parameters were compactness, stickiness, firmness and

sourness. The idli were prepared according to the framed design. The semi-trained panel

members evaluated the idli using a 15mm rating scale. Data were analyzed using RSM

and constraints were imposed on the experimental results as in Chapter 3. On sensory

analysis followed by RSM analysis of idli prepared from various combinations of

ingredients fermented at different duration up to 14 h, rice and dhal combination of

3:1.475 fermented to 10.2 h was found to be the best accepted product.

Principal Component Analysis was done to find the interrelationship between the sensory

attributes of the idli. The PCA analysis revealed that PC1 and PC2 accounted for 78% of

the total variance in the data matrix. It was clear that sensory attributes like sponginess

and fluffiness associated with each other strongly on the positive side of the PC1 axis

while firmness, compactness, stickiness were clustered together on the negative side of

the PC1 axis. The third cluster is formed by fermented aroma and sourness on the

positive side of PC2 axis. Sample from the experimental design point 6 was closely

associated with desirable sensory attributes like sponginess and fluffiness followed by

sourness and fermented aroma. On the other hand, design points 5, 1 and 2 were closely

correlated with undesirable sensory attributes like firmness, compactness and stickiness.

134

The texture and sensory data were analyzed together by imposing constraints on the

principal parameters of idli resulting in an optimized ratio of 3:1.18 with a fermentation

time of 12.02 h.

Chapter 5 dealt with the chemical components of nutritional importance in the optimized

product. The final product was low in fat indicating the break down into fatty acids

during fermentation. Analysis of fatty acid profile and oligosaccharide profile was done

using LCMS. The fatty acids namely Decanoic acid, Octadecanoic acid and

Hexadecanoic acid were of high relative abundance in idli compared to unfermented

batter. Regarding the oligosaccharide profile, the sugars namely trehalose, maltose,

melezitose, maltotriose, maltotetrose and maltopentose were formed during fermentation.

Results showed that the process of fermentation has led to the increase in nutrient content

of the idli.

Chapter 6 aimed to improve the shelf-life of the batter using modified atmosphere

packaging. Respiration dynamics was studied out to find the percentage of oxygen

utilized and percentage of carbon dioxide released during fermentation of batter. Three

packaging materials namely low density poly ethylene (LDPE), Poly propylene (PP),

High Molecular (HM) of varying thickness were used for packing the idli batter. Twenty

three gas combinations were used for MAP. The MAP packaged batter was stored at

30C and analyzed for gas mixture followed by texture and sensory analysis of the

product during the storage period. The results of the respiration dynamics of the idli

batter showed that the batter consumed 7% of O2 and evolved 12.6- 13% CO2 at 12.02 h

fermentation time. From this study it can be concluded that RTC idli batter packaged in

medium thickness LDPE flushed with 0% CO2 and 7.5 to 15% O2 could increase the

shelf-life up to seven fold increase without compromising the sensory qualities at 30C.

135

Practical implications / Recommendations

Based on the results and interpretations of this work following recommendations can be

made to further improve the commercial prospects of ready to cook idli batter.

1. A detailed survey on the consumer perception and acceptance as well as problems

associated with the currently available packaged ready to cook idli batter should

be done to estimate the true potential of commercial ready to cook idli batter.

2. Detailed study on shelf-life of Modified atmosphere packaged batter under

refrigerated conditions should be done.

3. In-depth instrumental analysis of flavour and aroma compounds needs to be done.

136

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Annexure-I

ORAL INTERVIEW SCHEDULE

1. Name :

2. Age :

3. Sex : a) Male b) Female

4. Address :

5. Educational qualification:

7. Occupation:

8. Monthly income:

9. Marital status: a) single b) married

10. Type of family: a) nuclear b) joint

11. Native place:

12. At what time do you take breakfast?

a) 7-8 am b) 8-9 am) 9-10 am

13. Do you skip breakfast?

a) Yes b) No

14. If yes, reasons to skip breakfast?

15. What are the food items you prefer for breakfast?

a) Idly b) Dosai c) Poori d) Chapatti e) Oats

16. What are the breakfast items you usually prepare?

17. How often do you consume idly?

a) Weekly b) Daily c) Monthly

18. How long years are you consuming Idli?

19. Do you like Idli?

a)Yes b) No

155

20. Do you prepare Idli at home?

a) Yes b) No

21. If no, from where do you get Idli?

a)Hotel b) Idli stall

22. Do you buy as Idli batter?

a) Yes b) No

23. Which is convenient to buy?

a) Batter b) Idli

24. How often do you buy Idli batter?

a) Daily b) Weekly c) Monthly

25. Where do you buy Idli batter?

a) Household b) Departmental store

26. What is the brand name?

27. Do you buy Idli batter in the same or different shop?

28. Do you store the purchased batter or buy only when necessary?

29. Do you enquire about the ingredients and quality of the Idli batter while buying?

a) Yes b) No

30. Do you like the quality of that Idli batter?

a) Yes b) No

31. Does the Idli prepared from such batter taste good?

a) Yes b) No

32. Do you prepare dosa from such batter?

a) Yes b) No

33. Do you check the manufacturing date while buying?

a) Yes b) No

156

34. Does the purchased Idli batter contain required amount of salt?

a)Yes b) No

35. What will be consistency of the purchased Idli batter?

a) Thick b) thin c) Normal

36. What will be the texture of the purchased Idli batter?

a) Smooth b) coarse

37. Why do you prefer to buy Idli batter rather than preparing at home?

a)Convenient b)Taste good c) Time saving d) Any other please specify

38. Do you buy Idli batter as cups measurement or in packet?

a) Cup b) Packet

39. What is the cost of one cup of batter?

40. What is the cost of one packet of batter?

41. How many Idli can be made from one cup or one packet of batter?

42. Do you think it is hygienic to buy as batter?

a)Yes b) No

43. What will be the colour of Idli prepared from purchased batter?

44. Do you grind Idli batter at home?

a) Yes b) No

45. How often do you grind for Idli?

a) Once in a week

b) Twice a week

c) Daily

d) Once in a month

46. In what proportion you take rice and dhal?

a) 3:1 b) 3:1.5 c) 3:2

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47. Which variety of rice and dhal you use?

48. Do you always use same variety of rice and dhal?

a) Yes b) No

49. Have you used with some other varieties of rice and dhal? Why?

a) Yes b) No

50. How many times do you wash the rice and dhal before soaking?

51. What is the quantity of water you use to soak the rice and dhal?

52. For how many hours do you soak?

53. When do you usually grind the rice and dhal?

a) Morning b) Afternoon c) Evening d) Night

54. Do you mix any additional ingredient along with dhal?

a) Yes b) No

55. What are the additional ingredients you use?

a) Rice flakes b) fenugreek c) Any other please specify

56. If yes, what is the proportion of the additional ingredient?

57. What is the purpose of the additional ingredient?

58. Which ingredient do you grind first?

a) Rice b) Dhal

59. Which equipment you use to grind?

a) Grinder

b) Mixie

c) Hand pound

60. Which do you think is the best equipment for grinding Idli batter?

61. Does the dhal that you use increase in volume while grinding?

a) Yes b) No

158

62. If it does not increase in volume what will be the impact on Idli?

63. How long will you grind rice and dhal?

64. Do you grind them together or separately?

65. Till what consistency do you grind rice and dhal?

a)Thick b)Thin c) Normal

66. What will be the texture of mixed batter?

a)Coarse b) smooth

67. What will be the consistency of Idli batter after mixing?

68. Do you add salt before or after fermentation?

69. How long do you leave the batter for fermentation?

70. Do you add curd or yeast to favor fermentation?

a) Yes b) No

71. What kind of vessel do you prefer to ferment the batter?

a) Plastic b) Ever silver c) Mud pot d) Any other

72. Do you mix the batter with hand or ladle?

73. Whom do you prefer to mix batter and so why?

74. Does your batter get fermented overnight?

a) Yes b) No

75. Does the batter volume increase after fermentation?

a) Yes b) No

76. Do you get any respective flavour from fermented batter?

a) Yes b) No

77. Usually what will be the colour of your Idli?

a) White

c) Light yellow

159

78. If the batter does not ferment do you get better Idli?

a) Yes b) No

79. How do you control fermentation to increase the shelf life of the batter?

80. Do you prepare dosa from the same batter?

a) Yes b) No

81. If the acidity increases, do you use that batter to prepare Idli?

a) Yes b) No

82. Which utensil do you prefer to prepare Idli?

a) Idli cooker b) Idli vessel

83. How many minutes do you steam?

84. How will you check if the Idli is cooked or not?

85. Do you give Idli as lunch for school going children?

a) Yes b) No

86. How many times do you take Idli per day when the batter is available?

87. Do you prepare Idli regularly or only when some is sick at home?

a) Yes b) No

88. Do you give Idli for the sick people?

a) Yes b) No

89. Why do you prefer Idli during convalescent period?

90. Is your consumption of Idli increased when compared to the past years?

91. What do you think is the main reason?

92. Why don‘t go buy Idli as batter to prepare Idli?

93. If it is a hygienically prepared, healthy batter will you be ready to buy?

a) Yes b) No

160

Annexure-II

Sensory analysis score card for Idli

Name: ___________ Date: ___________

-Taste the given samples and indicate intensity of perceived attributes by marking on the line at

appropriate place.

-Cleanse your palate with water in between samples.

COLOUR

---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ----

Low High

APPEARANCE

Fluffiness

---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ----

Low High

Compactness

---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ----

Low High

TEXTURE

Sponginess

---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ----

Low High

Firmness

---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ----

Low High

Stickiness

---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ----

Low High

AROMA

Fermented

---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ----

Low High

161

TASTE

Sour

---- | ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ----- . ---- | ----

Low High

OVERALL QUALITY

---- | ----- . ----- . ----- . ----- . ----- . ----- . --|-- . ----- . ----- . ----- . ----- . ----- . ---- | ----

Very Poor Fair Very Good

Comments:

Signature:

162

List of Publications

1. Transition in the Preparation and Consumption of Idli among the People of

Puducherry, Durgadevi, M and Prathapkumar H. Shetty, Indian Journal of

Nutrition and Dietetics (In Press).

2. Effect of Ingredients on Texture Profile of Fermented Food- Idli, Durgadevi, M

and Prathapkumar H. Shetty APCBEES Procedia Journal (In Press).

3. Effect of Ingredients on Sensory Profile of Idli using Response Surface

Methodology, Durgadevi, M and Prathapkumar H. Shetty, Journal of Food

Science and Technology (Under revision).

List of Proceedings

1. Presented a poster entitled ―Perception and consumption pattern of idli among the

people of Puducherry‖ in the International conference on Traditional foods (Dec

1-3, 2010) conducted at Pondicherry University.

2. Presented a poster entitled ―Process optimization of the texture and sensory

attributes of idli using response surface methodology (RSM)‖ in the National

conference on Agro Food Processing Technologies (Nov 3-4, 2011) conducted at

Pondicherry University.

3. Presented a poster entitled ―Effect on ingredients on the texture and sensory

attributes of an Indian fermented food, Idli‖ in the Fifth International Conference

on Fermented foods, health status and social well being: Challenges and

Opportunities (Dec 15-16, 2011) at CFTRI, Mysore.

modified atmosphere packaging of ready to cook …dspace.pondiuni.edu.in/jspui/bitstream/1/1685/1/m....

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