IMPACT OF THERMAL AND NON-THERMAL PROCESSING TECHNIQUES ON APPLE AND ...

170 Pages·2010·1.54 MB·English

IMPACT OF THERMAL AND NON-THERMAL PROCESSING TECHNIQUES ON
APPLE AND GRAPEFRUIT JUICE QUALITY

By

ZAREENA AZHU VALAPPIL

A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

2010
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© 2010 Zareena Azhu Valappil

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To my daughter Suha and my husband, Niyas

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ACKNOWLEDGMENTS
I would like to thank my advisor, Dr. Russell Rouseff, for his guidance and
unending support throughout the course of my research work. It would not have been
possible to conduct my research at the United States Department of Agriculture without
his help and encouragement. I would also like to thank my committee members: Dr. M.
Marshall, Dr. B. Ache, Dr. W. Yang and Dr. H. Zhang. I would also like to thank my
previous committee members, Dr. M. Balaban and Dr. S. Talcott, who have left
University of Florida. My specials thanks to Dr. Fan, Dr. Geveke and Dr. Zhang at
USDA for helping me successfully conduct my research at USDA.
I would also like to thank my lab mates Kim, Jen, Kym, Glen and Tim for their
constant help and support and for making my life easier and enjoyable at USDA. A
special thanks to Kim for all her help in the lab and participating in GCO and sensory
work. I also want to thank my Mom and Dad for their love and guidance throughout my
life. Finally, I would like to thank my husband Niyas and daughter Suha for supporting
and helping me achieve my goals. Lastly, I want to thank God for everything.
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TABLE OF CONTENTS

page
ACKNOWLEDGMENTS .................................................................................................. 4
LIST OF TABLES ............................................................................................................ 9
LIST OF FIGURES ........................................................................................................ 11
ABSTRACT ................................................................................................................... 13
CHAPTERS
1 INTRODUCTION .................................................................................................... 15
2 LITERATURE REVIEW .......................................................................................... 18
Flavor Perception .................................................................................................... 18
Fruit Flavors ............................................................................................................ 22
Apple Juice/Cider Aroma .................................................................................. 22
Grapefruit Juice Aroma .................................................................................... 25
Volatile Extraction ................................................................................................... 28
Gas Chromatography Olfactometry ........................................................................ 30
Processing .............................................................................................................. 31
Thermal Pasteurization .................................................................................... 32
Citrus juice thermal processing .................................................................. 33
Apple juice thermal processing .................................................................. 33
Effect of Thermal Pasteurization on Juice Flavor ............................................. 34
Non-Thermal Processing Methods ................................................................... 36
Pulsed electric field .................................................................................... 38
Radio frequency electric field ..................................................................... 45
Ultraviolet radiation .................................................................................... 46
3 COMPARISON OF THERMAL AND NON-THERMAL TECHNIQUES ON
APPLE CIDER STORAGE QUALITY UNDER EQUIVALENT PROCESS
CONDITIONS ......................................................................................................... 55
Introduction ............................................................................................................. 55
Materials and Methods............................................................................................ 56
Determination of Processing Conditions That Achieve 6-log Reduction of E.
coli K12 ......................................................................................................... 56
Ultraviolet process ..................................................................................... 56
Pulsed electric field process ....................................................................... 57
Thermal process ........................................................................................ 58
Shelf-Life of Processed Apple Cider ................................................................. 58
Processing and packaging ......................................................................... 58
Storage ...................................................................................................... 59
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Microbial tests ............................................................................................ 59
pH .............................................................................................................. 60
Brix ............................................................................................................. 60
Color .......................................................................................................... 60
Statistical Analysis ............................................................................................ 61
Results and Discussion........................................................................................... 61
Optimization of Equivalent Processing Conditions ........................................... 61
Effect of Thermal and Non-Thermal Processing on Microbial Stability During
Storage of Apple Cider .................................................................................. 63
Effect of Thermal and Non-Thermal Processing on Appearance of Apple
Cider During Storage .................................................................................... 65
Effect of Thermal and Non-thermal Processing on the pH and Brix of Apple
Cider During Storage .................................................................................... 65
Effect of Thermal and Non-Thermal Processing on Color of Apple Cider
During Storage .............................................................................................. 66
Conclusion .............................................................................................................. 68
4 IMPACT OF THERMAL AND NON-THERMAL PROCESSING
TECHNOLOGIES ON APPLE CIDER AROMA ...................................................... 74
Introduction ............................................................................................................. 74
Materials and Methods............................................................................................ 74
Apple Cider ....................................................................................................... 75
Apple Cider Processing .................................................................................... 75
Heat treatment ........................................................................................... 76
Ultraviolet treatment ................................................................................... 76
Pulsed electric field treatment .................................................................... 76
Packaging and Storage .................................................................................... 77
Microbial Stability ............................................................................................. 77
Volatile Extraction ............................................................................................. 78
Gas Chromatography-Mass Spectrometry Analysis ......................................... 78
Quantification of Apple Cider Volatiles ............................................................. 79
Sensory Evaluation .......................................................................................... 79
Statistical Analysis ............................................................................................ 80
Results and Discussion........................................................................................... 81
Microbial Stability During Storage .................................................................... 81
Volatile Composition ......................................................................................... 81
Odor Activity Values ......................................................................................... 82
Effect of Treatment and Storage on Volatiles ................................................... 83
Effect of Treatment and Storage on Odor Activity Values of Volatiles .............. 85
Aroma Sensory Studies .................................................................................... 86
Conclusion .............................................................................................................. 87
5 COMPARISON OF THERMAL AND NON-THERMAL TECHNIQUES ON
GRAPEFRUIT JUICE STORAGE QUALITY UNDER EQUIVALENT PROCESS
CONDITIONS ......................................................................................................... 92
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Introduction ............................................................................................................. 92
Materials and Methods............................................................................................ 93
Determination of Equivalent Treatment Conditions .......................................... 93
Heat treatment ........................................................................................... 93
Ultraviolet treatment ................................................................................... 93
Pulsed electric field treatment .................................................................... 94
Radio frequency electric field treatment ..................................................... 94
Shelf Life Study ................................................................................................ 95
Grapefruit juice pasteurization ................................................................... 95
Packaging and storage .............................................................................. 95
Microbial assay .......................................................................................... 96
Pectin methyl esterase activity assay ........................................................ 96
Ascorbic acid assay ................................................................................... 97
Non enzymatic browning ............................................................................ 97
pH .............................................................................................................. 98
Brix ............................................................................................................. 98
Color .......................................................................................................... 98
Statistical Analysis ............................................................................................ 99
Results and Discussion........................................................................................... 99
Effect of Treatments on Microbial Inactivation .................................................. 99
Effect of Treatments on Microbial Stability During Storage ............................ 101
Effect of Treatments on Pectin Methyl Esterase Activity ................................ 102
Effect of Treatments on Non-enzymatic Browning ......................................... 104
Effect of Treatments on Ascorbic Acid Degradation ....................................... 105
Effect of Treatments on Color ......................................................................... 106
Effect of Treatments on pH, Brix and Total Acidity ......................................... 107
Conclusion ............................................................................................................ 107
6 IMPACT OF THERMAL AND NON-THERMAL PROCESSING
TECHNOLOGIES ON AROMA OF RED GRAPEFRUIT JUICE: GC-
OLFATOMETRIC COMPARSION ........................................................................ 118
Introduction ........................................................................................................... 118
Materials and Methods.......................................................................................... 119
Grapefruit Juice .............................................................................................. 119
Grapefruit Juice Processing ........................................................................... 120
Heat treatment ......................................................................................... 120
Non-thermal juice treatments .................................................................. 120
Packaging and storage ............................................................................ 120
Extraction of Grapefruit Juice Volatiles ........................................................... 121
Volatile Analysis of Grapefruit Juice Volatiles ................................................. 121
Sensory Evaluation ........................................................................................ 122
Screening and training of panelists .......................................................... 122
Test method ............................................................................................. 123
Statistical Analysis .......................................................................................... 124
Results and Discussion......................................................................................... 124
Effect of Treatment and Storage on Grapefruit Juice Volatiles ....................... 124
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Gas Chromatography Olfactometry Profile of Grapefruit Juice ....................... 125
Gas Chromatography Olfactometry Profile Comparison of Fresh Untreated
and Treated Juice at Week 0 ...................................................................... 128
Thermal treatment .................................................................................... 129
Ultraviolet treatment ................................................................................. 130
Pulsed electric field treatment .................................................................. 131
Radio frequency electric field treatment ................................................... 131
Gas Chromatography Olfactometry Comparison of Fresh Untreated and
Treated Juice at Week 4 ............................................................................. 131
Sensory Evaluation ........................................................................................ 132
Conclusion ............................................................................................................ 133
7 CONCLUSION ...................................................................................................... 143
APPENDIX
A CHANGE IN APPLE CIDER APPEARANCE DURING STORAGE ...................... 146
B CALIBRATION TABLE FOR APPLE CIDER VOLATILES .................................... 147
C GRAPEFRUIT JUICE VOLATILE CONCENTRATION ......................................... 148
D GRAPEFRUIT JUICE SENSORY RESULTS ....................................................... 152
E SAMPLE SENSORY BALLOT FOR DIFFERENCE FROM CONTROL TEST ...... 154
LIST OF REFERENCES ............................................................................................. 155
BIOGRAPHICAL SKETCH .......................................................................................... 170

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LIST OF TABLES
Table page

2-1 Time – temperature parameters for PE inactivation in citrus juices .................... 52
3-1 Change in pH and Brix values for fresh*, thermal, UV and PEF treated apple
cider stored at 4 ºC for 4 weeks .......................................................................... 72
3-2 Change in Hunter color values** for fresh*, thermal, UV and PEF treated
apple cider stored at 4 ºC for 4 weeks ................................................................ 73
4-1 Effect of thermal and non-thermal treatments on apple cider volatiles
compared to fresh untreated cider after 4 weeks of storage at 4 ºC ................... 89
4-2 Effect of thermal and non-thermal treatments on odor activity values (OAV) of
apple cider volatiles after 4 weeks of storage at 4 ºC ......................................... 91
5-1 Yeast & mold count in control, thermal, UV, PEF and RFEF treated grapefruit
juice stored at 4 ºC for 4 weeks ........................................................................ 111
5-2 pH, Brix and total acidity (TA) values for control, thermal, UV, PEF and RFEF
treated grapefruit juice stored at 4 ºC for 4 weeks ............................................ 117
6-2 GCO analysis results of pasteurized and unpasteurized grapefruit juice .......... 136
6-3 Calculated total aroma intensity values for pasteurized and unpasteurized
grapefruit juice belonging to five odor categories ............................................. 138
6-4 GCO comparison of pasteurized grapefruit juice at week 4 to unpasteurized
grapefruit juice at week 0 .................................................................................. 140
6-5 Results of ANOVA for mean values from difference from control test .............. 142
6-6 Difference in means between pasteurized and unpasteurized grapefruit juice . 142
6-7 Results of ANOVA of mean values from difference control test at week 4 ....... 142
6-8 Difference in means between pasteurized and unpasteurized grapefruit juice
at week 4 .......................................................................................................... 142
B-1 Regression equation for standard compounds ................................................. 147
C-1 Volatile concentration (μg/L) in untreated (control) and treated grapefruit juice
at week0 ........................................................................................................... 149
C-2 Volatile concentration (μg/L) in untreated (control week 0) and treated
grapefruit juice at week 4 .................................................................................. 150
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D-1 Difference from control data between hidden control (unpasteurized juice)
and pasteurized juices (thermal, PEF, RFEF and UV) at week 0 ..................... 152
D-2 Difference from control data between hidden control (unpasteurized fresh
juice ) and pasteurized juices (thermal, PEF, RFEF and UV) at ....................... 153

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