efficacy of uv irradiation as an alternative...

EFFICACY OF UV IRRADIATION AS AN ALTERNATIVE NON-THERMAL

PASTEURIZATION METHOD TO PRODUCE MINIMALLY PROCESSED JUICE FROM

CONCORD, NIAGARA AND RIESLING GRAPES

A Project Paper

Presented to the Faculty of the Graduate School

of Cornell University

In Partial Fulfillment of the Requirements for the Degree of

Master of Professional Studies in Agriculture and Life Sciences

Field of Food Science and Technology

by

Vanessa Paola Moncayo Herrera

May 2015

ABSTRACT

The use of UV light as a safe alternative to thermal pasteurization was approved by

FDA in 2000. This study evaluates the efficacy of UV treatment to produce safe grape

juice from three varieties (Concord, Niagara and Riesling) through microbiological

validations and shelf-life studies. Grape juices were inoculated with approximately 107

CFU per mL of E.coli ATCC 25922, a surrogate for E. coli O157:H7, and exposed to a

UV dosage of 14 mJ·cm-2 using CiderSure 3500, a common commercial UV pasteurizer.

Regardless of the grape variety, reductions greater than 5 log10 were achieved. Results

from shelf-life studies showed that UV treated grape juices have a shelf-life of one to

two weeks under refrigerated conditions (7°C).

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BIOGRAPHICAL SKETCH

Vanessa Moncayo was born in July 1988 in New Jersey and moved to Quito, Ecuador.

She graduated with a B.S in Food Engineering in 2013 from San Francisco de Quito

University. In 2014, she obtained the “Universities of Excellence Scholarship” provided

by the Ecuadorian government which let her pursue her Master in Professional Studies

(MPS) degree at Cornell University. Under the advice of Dr. Olga Padilla-Zakour,

Vanessa studied the application of UV light as a non-thermal pasteurization treatment

for grape juices. In addition, Vanessa served as a Quality Assurance intern in Cornell

Dairy Plant for two semesters. Through her time at Cornell University Vanessa received

the “2014-2015 Western NY IFT Scholarship” for outstanding achievement in Food

Science graduate studies, as well as the “2014-2015 Goya Foods Prize” for outstanding

graduate student in the field of Food Science & Technology working in the area of fruits

and vegetables. Her interest in product development brought her to lead the 2014-2015

Ocean Spray Product Development team, which took the first place in the competition.

After graduating from Cornell University, Vanessa will return to Ecuador and will work

for the food industry in the area of product development.

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To my beloved family who inspires me to pursue my dreams <3

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ACKNOWLEDGMENTS

First, I would like to thank God for his pouring blessings over my life!

Thanks to my dear advisor Dr. Olga Padilla-Zakour for her support, kindness and

guidance as well as her encouragement and care throughout my time in Cornell. I

couldn’t be happier for having an advisor like her. Thanks to John Churey for his

unconditional help, for patiently answering all of my questions and making the lab in

Geneva exciting. To Herbert Cooley and Tom Gibson, thanks for their gentleness and

assistance in the pilot plant. Thanks to Jessie Usaga for her kindness and guidance in

this project. Thanks to Deanna Simmons and Tim Barnard for their daily support and

care and for sharing their Dairy Science knowledge with me. I will miss you so much!

Thanks to my wonderful family for being my pillar and believing in me. Thanks for the

unconditional love, care and prayers all the way from Ecuador.

To my awesome and fun lab mates Michelle Maldonado, Marcela Villareal, Marcela

Patino and Liz Buerman for making the lab such an enjoyable and happy place to be.

Thanks to Charles Lee, Michelle Maldonado and Kent Hsieh for being my family in

Ithaca and for all the unforgettable memories we had together: Michelle thanks for

sharing this experience with me, you have been the best roommate, friend and lab

mate! Kent thanks for making me laugh and for cooking the best Chinese food ever!

Charles, thanks for your love, care, support and for inspiring me to be better!

Thanks to the Ecuadorian Government, SENESCYT (Secretaria de Educacion Superior

Ciencia Tecnologia e Innovacion) for funding my graduate studies.

Finally, thanks to Cornell for making me feel at home during this time, I would never

forget this place and its lovely people!

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TABLE OF CONTENTS

ABSTRACT

BIOGRAPHICAL SKETCH .............................................................................................. iii

ACKNOWLEDGMENTS ................................................................................................. v

LIST OF FIGURES ........................................................................................................ viii

LIST OF TABLES .......................................................................................................... viii

INTRODUCTION ............................................................................................................. 1

Importance of Grape Production in United States ....................................................... 1 Juice Processing.......................................................................................................... 2 UV irradiation ............................................................................................................... 3 UV Disinfection System ............................................................................................... 5 CiderSure 3500 ........................................................................................................... 6 Objectives .................................................................................................................... 8 General Objective ........................................................................................................ 8 Specific Objectives ...................................................................................................... 9

MATERIALS AND METHODS ........................................................................................ 9

Grape Juices ............................................................................................................... 9 Physicochemical measurements ............................................................................... 10 UV Treatment ............................................................................................................ 10 Microbiological Validation: UV light treatment ............................................................ 11 Shelf Life Study ......................................................................................................... 12 Statistical Analyses .................................................................................................... 12

RESULTS AND DISCUSSION ...................................................................................... 13

Shelf-life Study .......................................................................................................... 13 Validation Study ......................................................................................................... 18

CONCLUSIONS ............................................................................................................ 21

FUTURE WORK ........................................................................................................... 21

APPENDIX .................................................................................................................... 22

Raw Juice Microbiological Data ................................................................................. 22 Shelf-life Study Data .................................................................................................. 23 Microbiological Validation Data .................................................................................. 26

REFERENCES .............................................................................................................. 28

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LIST OF FIGURES

Figure 1. CiderSure 3500 Diagram ............................................................................... 6

Figure 2. Yeast & Mold (PDA) counts of refrigerated UV-processed grape juices ...... 16

Figure 3. Total aerobes (PCA) counts of refrigerated UV-processed grape juices ...... 17

Figure 4. Average log-reductions of E. coli ATCC 25922 achieved in inoculated grape

juices after exposure to UV treatment .......................................................... 20

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LIST OF TABLES Table 1. Physico-chemical characterization of grape juices for shelf-life studies .......... 13

Table 2. Microbiological counts of grape juices before and after UV treatment ............. 15

Table 3. Pysico-chemical characterization of grape juices used for microbiological

validation of UV treatment ............................................................................... 18

Table 4. Efficacy of UV treatment reducing E. coli ATCC25922 in inoculated juices ... 19

1

INTRODUCTION

Importance of Grape Production in United States

Grape is a high value fruit crop in the United States. In 2014, there were 1,049,600

acres of grape bearing land in the United States, with New York State accounting for

37,000 acres. The total production of grapes in the United States was 7,769,630 tons,

of which 188,000 tons were produced in the State of New York. The utilized production

of grapes in the country in 2014 was about 7,757,480 tons. Only 13% of the total

utilized production of grapes were destined to fresh consumption, while 87% (6,744,560

tons) were destined for processing. Processed grape utilization has an average value

per ton of $629 which means that in the United States the processed grapes utilization

value was $4,244,132,000 dollars in 2014 (USDA, 2015).

The grape utilization for juice processing increased from 346,950 tons in 2012 to

549,920 in 2014, with an average price of $206 per ton of juice produced.

Concord and Niagara grapes represent an important part of the grapes used for used

processing purposes in the US. Concord grape processed utilization rose by 62%, from

310,140 tons in 2012 to 505,290 tons in 2014, while Niagara grapes processed

utilization experienced a rise of 40% from 50,150 tons in 2012 to 70,370 in 2014

(USDA, 2015).

Concord, Riesling and Niagara grapes are cultivated in the State of New York.

Regarding wine and juice grape production, New York State Department of Agriculture

and Markets reports that the state ranks number three behind California and

Washington State. Grapes used for juice production in New York State accounted for 62

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percent of the total grapes consumed, being 36 percent destined to wine production and

only 2 percent for fresh market. The four main grape producing zones in New York

State are: Lake Erie area, the Finger Lakes area, the Hudson Valley and the eastern

end of Long Island.

Juice Processing

Pasteurization of juice is fundamental to guarantee consumers’ safety. Due to history

of fruit and vegetable juice foodborne illness outbreaks, FDA has established the Juice

Hazard Analysis & Critical Control Points (HACCP) regulation. The regulation states

that a 5-log pathogen reduction must be accomplished for the microbe identified as the

"pertinent microorganism," which is the most resistant microorganism of public health

significance that is likely to occur in the specific juice (FDA, 2004).

Traditionally juices are processed with the application of a heat treatment as a way to

reduce pathogens and spoilage microorganisms. High temperature short time (HTST)

process is the most common method used for juice pasteurization, being aseptic

processing another common heat treatment used for pasteurization. Thermal treatment

is the most efficient and widely used method for pasteurization used in the juice

industry. However, it also brings along undesirable side effects in the product, mainly

loss of sensory attributes (Ortega-Rivas, 2012).

Consumers’ demand for fresher products with better nutritional properties had increased

in the last years. Customers are looking for authentic taste, safer and healthier

products, and natural fresh foods, as well as “green” foods that can be produced in a

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more environmentally friendly way with sustainable methods and smaller carbon

footprints (Koutchma, 2009).

These consumers’ demands have incentivized the exploration of non-thermal methods,

such as ultraviolet (UV) irradiation, in order to find balance between microbiological

safety and premium sensory quality of processed foods (Ortega-Rivas, 2012). Special

attention has been given to UV application in fresh fruit juices, since FDA approved in

2000 the use of UV-light as a safe alternative treatment to thermal pasteurization of

these products. (Koutchma, 2008). UV has been well studied and established for

treatment of water, air and surface decontamination, yet for liquid foods is still limited

and further studies need to be completed. Liquid foods such as juices present a variety

of optical, as well as physical properties and varied chemical compositions, factors

which influence UV light transmittance, dose, momentum transfer, and as a

consequence microbial inactivation (Koutchma, 2009). UV irradiation has experienced

a rapid acceptance by the juice industry. It is a convenient choice for producers due to

its low capital investment cost, either as a process or when introducing a continuous

inline UV system, compared to other pasteurization methods (Datta & Tomasula, 2015).

Moreover, UV pasteurization is considered a highly efficient process, as well as low

maintenance and environmental friendly (Ortega-Rivas, 2012).

UV irradiation

Ultraviolet processing for disinfection purposes consist of the application of radiation

from the ultraviolet region. The usual wavelength for UV processing is somewhere from

100 to 400 nm. This range can be divided into UV-A (315 to 400 nm) accountable for

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tanning in human skin; UV-B (280 to 315 nm) responsible for causing skin burning and

ultimately could lead to skin cancer; UV-C (200 to 280 nm) “germicidal range” that

successfully inactivates bacteria and viruses; and the vacuum UV range (100 to 200

nm) which can be absorbed by most substances and therefore can be conducted

through vacuum. When exposed to UV treatment, DNA molecules absorb UV light

producing crosslinking between pyrimidine nucleoside bases thymine and cytosine in

the DNA strand. Due to the mutated base, establishment of the hydrogen bonds with

the purine bases on the opposite strand is impaired. Consequently, DNA transcription

and replication is blocked, compromising cellular functions and leading to death of the

cells, therefore the germicidal effect. Amount of crosslinking is proportionate to the

amount of UV exposure. A minimal dose of 400 J/m2 is necessary for microbial

inactivation to take place (FDA, 2013).

Irradiation effects on microorganisms are subjected to several factors such as: species,

strain, culture and growth phase. Moreover, the kind and composition of the specific

food to be irradiated has a significant influence on these effects. The use of UV light

with germicidal effects has been applied in three particular areas: air disinfection, liquid

sterilization and inhibition of surface microorganisms. In the food industry specific UV-C

irradiation applications include: disinfection of air and water, disinfection of surfaces of

fresh products such as meat, vegetable, poultry, fish, eggs; and pasteurization of

various liquid foods such as milk, fruit juice or cider (Falguera et al. 2011).

5

UV Disinfection System

An UV system consists of a reaction chamber for UV light treatment in the form of

concentric tubing or other designed tubes, an UV-C lamp, containers for the liquids

(juice), plastic tubing, refrigeration system and pumps. Inside the concentric tube

system there is an UV lamp surrounded by a quartz jacket. The liquid product travels

through the annular part of the tube to achieve the required germicidal effect. Usually,

thin films of liquid product are used in order to increase an effective penetration of UV

light into the product, using the laminar flow of liquids. The use of more than one

concentric tubing system increases the germicidal effect on the product without the

necessity to recirculate it through the system. Turbulent flow of the liquid product

promotes improved penetration of UV light as well, guarantying that the whole product

received the identical UV dose. In order to achieve a Log reduction of pathogens of 5 or

greater, the product should be exposed to a treatment dose of at least 400 J/m2 of UV

radiation (Datta & Tomasula, 2015).

Liquid products that can be treated with UV irradiation include: water, viscous sugar

syrup, fruit or vegetable juices, industrial effluents and others. The type of UV lamp

used for the process determines the type of UV technology, which can be classified as

low pressure and medium pressure. Low pressure lamps have a monochromatic UV

output (limited at 254 nm), while medium pressure lamps have a polychromatic output

(185 to 400 nm). The use of low pressure systems are usually more appropriate for

small, intermittent flow application. Medium-pressure systems represent a better fit for

higher flow rates (Ortega-Rivas, 2012).

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CiderSure 3500

The CiderSure 3500 is one of the most common commercial UV pasteurizers. This

apparatus passes fluid as a thin film on the UV exposed lamp, resulting in complete

penetration of UV light into the fluid. This reactor has eight lamps (Datta & Tomasula,

2015), and its flow rate is controlled by a computer interface that reads the UV

transmission using UV sensors (Koutchma et. al 2009).

Figure 1. CiderSure 3500 diagram

Validation procedure of new technology, such as UV irradiation includes validation of

microbiological safety. For performing microbiological validation studies, a target

pathogen of concern “pertinent pathogen” must be identified. The pertinent pathogen to

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be used in the challenge study should be selected based on literature review or

discussion with experts (Koutchma et. al, 2009).

The validation process consists of inoculating fruit juices with high levels of the target

microorganisms and expose juices to the UV treatment. By comparing the microbial

population before and after the treatment the log reduction can be calculated and

therefore the effectiveness of UV as a pasteurizing method can be determined (FDA,

2013)

Several studies have been done to validate UV treatment using CiderSure 3500 with

turbulent flow as a 5-log reduction method to pasteurize apple cider. Basaran et. al

(2004) used the CiderSure 3500 to examine the effect of eight different apple cultivars

upon UV inactivation of three strains of E. coli O157:H7. Strains used for this study

were ATCC 43889, ATCC 43895 and 933. The study found that all varieties of apple

juice reached a Log-reduction higher than 5. Another study evaluated the efficacy of

UV irradiation on the inactivation of Cryptosporidium parvum oocysts in fresh apple

cider using a CiderSure 3500A apparatus. Results found a greater reduction than 5-log

obtained by exposing contaminated apple cider to 14.32 mJ/cm2 for 1.2 to 1.9 seconds

(Hanes et. al, 2002). Furthermore, Dong et. al (2010) studied the reduction of patulin

mycotoxin in fresh apple cider by treating it with UV irradiation, with the CiderSure 3500

apparatus. Results showed that an UV exposure of 14.2 to 99.4 mJ.cm2 significantly

reduced the levels of patulin. Patulin levels decreased by 9.4 to 43.4% (depending on

the range of UV dose) after less than 15 s of UV exposure. Quintero-Ramos et. al

(2004) examined the effects of UV light dose (1800 to 20331 µJ/cm2) on the inactivation

of E. coli ATCC 25922 on apple cider. Results found that doses of 6500 µJ/cm2 or

8

higher resulted in the achievement of a greater than 5-log reduction of E. coli. Usaga

et. al (2014) performed validation studies of CiderSure 3500’s quartz tubes by treating

apple cider inoculated with Escherichia coli ATCC25922. An average of 7.0 ± 0.7 log

reductions of E. coli were obtained, being 5.01 log reduction the minimum value

achieved.

Furthermore, Matak et. al (2005) used CiderSure 3500 to study the effects of UV

exposure on the inactivation of Listeria monocytogenes on fresh goat milk. Results

showed that a greater than 5-log reduction can be achieved when milk received a

cumulative UV dose of 15.8 ±1.6 mJ/ cm2

Objectives

Several studies have been conducted to evaluate the efficacy of CiderSure 3500. Most

of these studies have proven the ability of CiderSure 3500 to obtain a log-reduction of at

least 5-log of pertinent pathogens in apple cider. Furthermore, these studies have

focused mainly on the validation of the process and the quality of treated apple cider.

Very limited information can be found regarding the application of UV treatment using

CiderSure 3500 in other juices than apple cider. Additionally, not many studies have

focused in the evaluation of UV treated juices’ shelf-life.

General Objective

The objective of this study is to apply UV irradiation technology using the CiderSure

3500 to produce non-thermal, minimally processed, high quality grape juices from

Concord, Niagara and Riesling varieties.

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Specific Objectives

To perform the shelf-life study of UV treated grape juices from Concord, Niagara

and Riesling varieties under refrigerated conditions.

To execute microbiological validation of UV light treatment using grape juices

inoculated with E. coli ATCC 25922 at 107 CFU/mL.

MATERIALS AND METHODS

Grape Juices

Three different varieties of grapes: Niagara, Riesling and Concord were used for this

study. All grapes were obtained from a grape yard located in Geneva, NY. Niagara and

Riesling grapes were stored at 0°C and thawed at 7°C for a period of seven days before

processing. Concord grapes were harvested and kept in refrigeration at 7°C for 7 days

before processing. Previous trial using frozen Concord grapes resulted in a purple

colored juice that was not able to be UV treated. Grapes were cold pressed on a

custom made hydraulic press rack and frame, pressing process was performed in 10 kg

batches.

Riesling juice was 17.8° Brix and had a pH value of 3.47. Niagara juice was 16.2 °Brix

and had a pH value of 3.47. Concord juice was 13.7 °Brix and had a pH value of 3.25.

Juice samples were packed into 125 mL (4 oz) Nalgene™ PET Sterile Square Media

Bottles with HDPE Closure (Thermo Scientific, Lima, Ohio).

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Physicochemical measurements

Grape juice samples were subjected to chemical and physical measurements in

triplicate. pH, titratable acidity (TA), soluble solids (°Brix), turbidity, absorption

coefficient and color (L, a, b) were measured. Accument Basic AB15 pH meter (Fisher

Scientific, Hampton, New Hampshire) was used to measure pH values. TA was

measured by the use of G20 Compact Titrator from Mettler Toledo. Five mL of juice

were sampled and diluted in 35 mL of distilled water. Results were reported as malic

acid percentage (w/v). An Auto ABBE Refractometer Leica 10504 (Leica Inc., Buffalo,

NY) was used to determine total soluble solids of juice, results were reported as °Brix.

Turbidity was measured using a Hach 2100P turbidimeter 4500-00 (Hach Co.,

Loveland, CO) and results were expressed as Nephelometric Turbidity Units (NTU).

Color measurement was performed in a Hunter UltraScan VIS spectrophotometer

(Hunter Lab Assoc., Reston, VA) and results were reported as L, a and b values.

Absorption coefficient (α) was calculated by following the protocol described by

Koutchma et al. (2004). Juice absorption was measured at 254 nm using a UV-1800

spectrophotometer (Shimadzu Scientific Instruments, Columbia, MD). Samples were

subjected to a 10-fold dilution in distilled water and positioned into demountable fused

quartz cuvettes of 0.1, 0.2, 0.5 and 1.0 mm path length (NSG Precision Cells, INC.,

Farmingdale, NY).

UV Treatment

Grape juices UV treatments were performed in the Cider Sure model 3500 UV juice

processing machine (FPE Inc., Rochester, NY) at a wavelength of 254 nm. This

11

machine adjusts the flow rate of the juice and provides a UV dosage of 14 mJ·cm-2.

After UV treatment, juice was manually packed in 125 mL (4 oz) PET Sterile Bottles and

stored at 7°C in a refrigeration chamber. Three samples of each juice were taken every

week for conducting microbiological testing (total plate count, mold & yeast) for the shelf

life study.

Microbiological Validation: UV light treatment

With a sterile loop a single colony of E. coli ATCC 25922 was picked from a petri dish

and inoculated into a culture tube containing 5 ml of TSB (Tryptic soy broth). The

culture was incubated for 5-6 hours at 35-37 °C and 200-250 rpm. One mL of the

culture was transferred into a 500 ml Erlenmeyer flask containing 100 mL of sterile

tryptic soy broth and was incubated for 16-18 hours at 35-37 ºC and 200-250rpm.

Samples of approximately 1.8 L of every variety of grapes were inoculated with 20 ml of

the E. coli ATCC 25922 solution, which is equivalent to an initial population of 107

CFU·ml-1. Juices were sampled and tested previous and after UV processing. Samples

were plated in duplicate, seven serial dilutions in 9 ml of sterile 0.1% peptone water

were made. One mL of each dilution was plated in the petri dishes and later pour-

plated with Trypticase soy agar and taken to incubation for 20 ± 2 h at 35 ± 2 °C. The

log reduction of E. coli ATCC25922 was calculated and reported as the difference

between the log-transformed counts before and after the exposure to UV treatment.

12

Shelf Life Study

Microbiological tests: total plate count, and molds and yeast count were performed

every seven days. Plating with plate count Agar (PCA), Difco, Becton Dickinson

(Sparks, MD) was performed to determine total aerobic microbes population. Plating

with acidified (3.5 pH) Potato Dextrose Agar (PDA), Difco, Becton Dickinson (Sparks,

MD) was performed to determine yeast and mold population. Three bottles of each

juice and treatment were taken for microbiological analysis. One mL of juice sample

was subjected to serial dilutions in 1% sterile peptone water and placed into Petri

dishes. Agar was poured and mixed thoroughly, a duplicate of each dilution was made.

Petri dishes were incubated for a period of 48 h at a temperature of 30°C. Results were

reported as log10 CFU/mL.

Statistical Analyses

Log-reductions among grape varieties were statistically analyzed by analysis of

variance. Statistical significance of difference between sample means were made using

Tukey’s HSD (honestly significant difference) test at significance levels of α=0.05 using

JMP Pro 10, SAS software.

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RESULTS AND DISCUSSION

Shelf-life Study

Concord juice had a light brown color, pH of 3.26 and soluble solids content of

13.69°Brix. Niagara and Riesling juices had higher pH of 3.47. Niagara and Riesling

juices had a light amber color, soluble solids content of 16.17 and 17.81°Brix. Concord

was the juice with higher turbidity with a value of 607 NTU. Values of absorption

coefficient and acidity were not significantly different among the varieties (α≤ 0.05).

Table 1. Physico-chemical characterization of grapes juices used for shelf-life studies

under refrigerated conditions (7°C)

Grape Variety

pH Soluble Solids (°Brix)

Titratable Acidity (% w/v malic acid)

Turbidity(NTU)

Color Components

Absorption Coefficient (mm-1)

L a b

Concord

3.26 ± 0.06 b

13.7 ± 0.60 b

0.64 ± 0.27 a

607 ± 75 a

28.13 ± 0.30 b

-0.03 ± 0.01 c

0.15 ± 0.07 c

0.175 ± 0.002 a

Niagara

3.47 ± 0.07 a

16.2 ± 1.2 a

0.370 ± 0.004 a

428 ± 18 b

28.44 ± 0.25 b

1.32 ± 0.02 b

2.44 ± 0.26 b

0.152 ± 0.012 a

Riesling

3.47 ± 0.01 a

17.81 ± 0.08 a

0.44 ± 0.04 a

330.33 ± 27 b

29.64 ± 0.21 a

1.44 ± 0.09 a

4.78 ± 0.28 a

0.158 ± 0.010 a

Means ± SD of 3 analytical replicates. Same letters indicate no significant difference at

95% confidence level.

14

Microbiological quality of raw juice was similar between Niagara and Riesling varieties

(α≤ 0.05) with total aerobes counts (PCA) of 55000 CFU/mL (4.73 log10) and 56500

CFU/mL (4.74 log10), and mold & yeast counts (PDA) of 20000 (4.16 log10) and 13033

CFU/mL (4.05 log10) respectively. Concord juice had poorer microbiological quality with

total aerobes counts (PCA) of 247000 CFU/mL (5.38 log10) and mold & yeast counts

(PDA) of 297160 CFU/mL (5.45 log10). UV irradiation decreased raw grape juice total

aerobe counts by 1.53 log10 for Concord, 1.22 log10 for Niagara and 1.25 log10 for

Riesling. Mold and yeast counts were reduced by 1.33 log10 for Concord, 0.65 log10 for

Niagara and 2.24 log10 for Riesling. Tandon et. al (2003)achieved higher reductions

(1.9 for total aerobes and 1.6 log10 for yeast & mold) when treating raw apple cider of

better microbiological quality.

Concord grape juice showed a shelf-life of 1 week under refrigerated conditions (7°C)

while Niagara and Riesling juices showed a shelf-life of 2 weeks under the same

conditions. Similar results of 1-2 weeks of shelf-life were reported by Tandon and

coworkers for UV treated apple cider (Tandon et. al, 2003).

For the three varieties of juice the end of shelf-life was determined by the appearance of

visual mold inside the bottles. These results correlate with previous studies done by

Choi who observed end of shelf-life in apple cider by mold and yeast spoilage (Choi &

Nielsen, 2005).

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Table 2. Microbial counts of grape juices from Concord, Niagara and Riesling varieties

before and after UV treatment with CiderSure 3500 UV juice processing machine.

Variety

Raw Juice Counts before UV treatment

(log10 CFU/mL)

Juice Counts after UV treatment (log10 CFU/mL)

Shelf-life

Total plate counts

Mold & yeast

Total plate counts Mold & yeast

Concord 5.38 5.45 3.85 4.12 7 days*

Niagara 4.73 4.16 3.51 3.51 15

days*

Riesling 4.74 4.05 3.49 2.69 15

days*

*end of shelf-life was determined by presence of visual mold.

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Figure 2. PDA plate counts during refrigerated storage (7°C) of UV processed grape juice packed in sterile PET bottles. * indicates end of shelf-life due to presence of visual mold inside the bottle.

17

Figure 3. PCA plate counts during refrigerated storage (7°C) of UV processed grape juices packed in sterile PET bottles. * indicates end of shelf-life due to presence of visual mold inside the bottle.

18

Validation Study

Concord juices used for shelf-life and validation studies were from the same production

batch. Juices from Niagara and Riesling varieties used for the validation study were

different from those used for shelf-life study, therefore their physico-chemical

characteristics are different.

Concord juice had a pH of 3.26 and a soluble solid content of 13.69°Brix. Niagara juice

had a 3.23 pH and 13.45°Brix soluble solids. Riesling juice had a pH value of 3.01 and

17.78°Brix soluble solids. The highest turbidity observed was from Concord at 607

NTU. Acidity was the only physical-chemical characteristic that was not significantly

different among all the grapes varieties (α≤ 0.05).

Table 3. Physico-chemical characterization of grapes juices used for validation of UV

treatment with CiderSure 3500 UV juice processing machine for E. coli ATCC 25922

Grape Variety

pH Soluble Solids (°Brix)

Titratable Acidity (%w/v malic acid)

Turbidity (NTU)

Color Components Absorption Coefficient (mm-1)

L a b

Concord

3.26 ± 0.06 a

13.69 ± 0.60 b

0.64 ± 0.27 a

607 ± 75 a

28.13 ± 0.30 c

-0.03 ± 0.01 c

0.15 ± 0.07 a

0.175 ± 0.002 a

Niagara

3.23 ± 0.04 a

13.45 ± 0.22 b

0.640 ± 0.004 a

156 ± 11 b

32.38 ± 0.56 b

2.67 ± 0.27 a

18.02 ± 1.02 b

0.099 ± 0.002 c

Riesling

3.01 ± 0.04 b

17.78 ± 0.19 a

0.67 ± 0.21 a

185 ± 12 b

33.84 ± 0.54 a

1.37 ± 0.40 b

18.78 ± 1.00 b

0.140 ± 0.004 b

Means ± SD of 3 analytical replicates. Same letters indicate no significant difference at 95% confidence level.

19

UV treatment significantly reduced E.coli ATCC 25922 in grape juices from Concord,

Niagara and Riesling varieties (α≤ 0.05), the average log reduction observed was

6.44±0.36. Log reduction was significantly different between the three varieties. The

lowest achieved reduction was 6.07 log10 obtained for Concord grape juice (Figure 3).

Table 4. Efficacy of UV treatment at 14 mJ·cm-2 reducing E. coli ATCC 25922 in

inoculated grapes juices from Concord, Niagara and Riesling varieties

Juice Variety Population Before UV exposure

log10 (CFU/mL) Population After UV exposure

log10 (CFU/mL)

Concord 7.72 1.64

Riesling 7.36 0.89

Niagara 7.62 0.83

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Figure 4. Average log10 reductions of E. coli ATCC 25922 achieved in inoculated grape

juices of Concord, Niagara and Riesling varieties after exposure to UV treatment at 14

mJ·cm-2. Same letters indicate no significant difference at 95% confidence level.

Regardless the variety of grape, a reduction greater than 5 log10 was achieved for the

studied juices. These results correlate with previous studies done by Basaran et. al

(2004) and Usaga et. al (2014) where log reductions higher than 5 were achieved when

treating apple cider with UV irradiation, under turbulent flow, at a dosage of 14 mJ·cm-2.

21

CONCLUSIONS Application of UV irradiation with CiderSure 3500 at 14 mJ·cm-2 under turbulent flow on

grape juices from Concord (cold pressed), Niagara and Riesling varieties achieved a

reduction of at least 5-log of E. coli ATCC 25922, representing an effective alternative to

thermal pasteurization treatment. UV irradiation produced quality grape juices with a

shelf-life between 7 and 15 days under refrigerated conditions (7°C). The end of shelf-

life for all the grape juices was determined by the presence of visual mold.

FUTURE WORK

Further studies should be done regarding the effects of UV treatment application with

CiderSure 3500 in grape juices. Different strains of Escherichia coli should be used for

the microbiological validation in order to determine which strain is more resistant to the

process. Moreover, more varieties of grapes could be evaluated to determine how the

physical-chemical properties of grape varieties affect the efficiency of the treatment.

Quality of UV treated grape juice could be evaluated by analyzing chemical and sensory

changes in the UV treated refrigerated samples through the shelf-life time.

Finally, the effect of the combination of UV treatment with other non-thermal treatments

should be studied in order to develop a process that allows the production of high

quality grape juice with longer shelf-life.

22

APPENDIX

Raw Juice Microbiological Data

CONCORD

Total Aerobes Count (PCA)

Rep Dilution Count

1 Count

2 Average Log Total 1 3 196 133 164.5 2.2162 5.22 2 3 348 280 314 2.4969 5.5 3 3 255 272 263.5 2.4208 5.42

Yeast & Mold Count (PDA)

Rep Dilution Count

1 Count

2 Average Log Total 1 3 174 179 176.5 2.2467 5.25 2 3 400 424 412 2.6149 5.61 3 3 346 260 303 2.4814 5.48

NIAGARA


Rep Dilution Count

1 Count

2 Average Log Total 1 3 65 49 57 1.7559 4.76 2 3 73 71 72 1.8573 4.86 3 3 38 36 37 1.5682 4.57


Rep Dilution Count

1 Count

2 Average Log Total 1 3 20 22 21 1.3222 4.32 2 3 43 27 35 1.5441 4.54 3 3 4 4 4 0.6021 3.6

23

RIESLING Total Aerobes Count (PCA)

Rep Dilution Count

1 Count

2 Average Log Total 1 3 33 48 40.5 1.6075 4.61 2 3 66 83 74.5 1.8722 4.87 3 3 55 54 54.5 1.7364 4.74


Rep Dilution Count

1 Count

2 Average Log Total 1 2 136 38 87 1.9395 3.94 2 3 9 38 23.5 1.3711 4.37 3 2 18 120 69 1.8388 3.84

Shelf-life Study Data

CONCORD


Day Rep Dilution Count

1 Count

2 Average Log Total

1 1 1 722 784 753 2.87 3.88 2 1 684 710 697 2.84 3.84 3 1 672 704 688 2.84 3.84

7 1 3 3 4 3.5 0.54 3.54 2 3 9 8 8.5 0.93 3.93 3 3 3 12 7.5 0.88 3.87

24


Daye Rep Dilution Count

1 Count

2 Average Log Total

1 1 1 1240 1216 1228 3.09 4.09 2 1 1408 1460 1434 3.16 4.15 3 1 1268 1324 1296 3.11 4.11

7 1 2 60 53 56.5 1.75 3.75 2 2 154 147 150.5 2.18 4.18 3 2 83 82 82.5 1.92 3.92

NIAGARA Total Aerobes Count (PCA)


1 Count

2 Average Log Total

1 1 2 29 22 25.5 1.41 3.41

2 2 35 25 30 1.47 3.48 3 2 49 42 45.5 1.66 3.66

7 1 4 2 3 2.5 0.39 4.39

2 4 14 18 16 1.20 5.20 3 4 11 26 18.5 1.27 5.27

14 1 2 86 70 78 1.89 3.89

2 2 15 5 10 1.00 3.00 3 3 3 3 3 0.48 3.48



1 Count

2 Average Log Total

1 1 2 27 22 24.5 1.39 3.39 2 2 14 11 12.5 1.09 3.091 3 2 122 108 115 2.06 4.06

7 1 4 2 2 2 0.30 4.30 2 4 1 1 1 0.00 4.00 3 4 1 1 1 0.00 4

14 1 2 34 29 31.5 1.49 3.49 2 2 6 16 11 1.04 3.04 3 2 10 17 13.5 1.13 3.13

25

RIESLING Total Aerobes Count (PCA)


1 Count

2 Average Log Total

1 1 1 222 91 156.5 2.19 3.19 2 1 334 392 363 2.56 3.56 3 1 603 462 532.5 2.73 3.73

7 1 4 1 1 1 0.00 4.00 2 4 10 10 10 1.00 5.00 3 4 5 8 6.5 0.816 4.81

14 1 2 16 19 17.5 1.245 3.24 2 2 12 13 12.5 1.09 3.09 3 2 46 35 40.5 1.61 3.61



1 Count

2 Average Log Total

1 1 1 9 11 10 1 2 2 1 88 12 50 1.69 2.69 3 2 10 17 13.5 1.13 3.13

7 1 3 4 3 3.5 0.54 3.54 2 3 1 1 1 0.00 3.00 3 3 1 1 1 0.00 3.00

14 1 2 8 15 11.5 1.06 3.06 2 2 34 20 27 1.43 3.43 3 2 9 1 5 0.69 2.69

26

Microbiological Validation Data

Concord juice inoculated with E. coli ATCC 25922

before UV treatment

Rep Dilution Count

1 Count


After UV treatment

Rep Dilution Count

1 Count

2 Average Log Total 1 0 39 36 37.5 1.57 1.57 2 0 37 69 53 1.72 1.72 3 0 33 51 42 1.62 1.62

Niagara juice inoculated with E.coli ATCC 25922

Before UV treatment

Rep Dilution Count

1 Count

2 Average Log Total 1 6 51 35 43 1.63 7.63 2 6 34 41 37.5 1.57 7.57 3 6 47 42 44.5 1.65 7.65

After UV treatment

Rep Dilution Count

1 Count

2 Average Log Total 1 0 11 14 12.5 1.09 1.09 2 0 4 5 4.5 0.65 0.65 3 0 7 4 5.5 0.74 0.74

27

Riesling juice inoculated with E.coli ATCC 25922

Before UV treatment

Rep Dilution Count

1 Count


After UV treatment

Rep Dilution Count

1 Count

2 Average Log Total 1 0 6 3 4.5 0.65 0.65 2 0 8 12 10 1.00 1.00 3 0 11 10 10.5 1.02 1.02

28

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