EFFECT OF THERMAL PROCESSING ON THE PHENOLIC ANTIOXIDANTS OF COLORED

268 Pages·2011·2.11 MB·English

EFFECT OF THERMAL PROCESSING ON THE PHENOLIC ANTIOXIDANTS OF
COLORED POTATOES

By

BALUNKESWAR NAYAK

A dissertation submitted in partial fulfillment of
the requirements for the degree of

DOCTOR OF PHILOSOPHY

WASHINGTON STATE UNIVERSITY
Department of Biological Systems Engineering

MAY 2011
To the Faculty of Washington State University:

The members of the Committee appointed to examine the dissertation of
BALUNKESWAR NAYAK find it satisfactory and recommend that it be accepted.

___________________________________
Juming Tang, Ph.D., Chair

___________________________________
Shyam S Sablani, Ph.D.

___________________________________
Jose De J Berrios, Ph.D.

___________________________________
Joseph R. Powers, Ph.D.

___________________________________
Jinwen Zhang, Ph.D.

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ACKNOWLEDGMENTS
I express my greatest gratitude to Dr. Juming Tang for his advice, guidance and
encouragement throughout my study and research at Washington State University. I am at a loss
of words to express the importance and value of his helpful insights, understanding, and moral
support that enabled me to stay focused on my research. I also express hearty thanks to my
doctoral committee members: Drs. Shyam S Sablani, Jose De D Berrios, Joseph R. Powers, and
Jinwen Zhang for their valuable suggestions and feedback whenever I approached them with
problems.
I thank Dr. Rui Hai Liu, Associate Professor in the Department of Food Science, Cornell
University, Ithaca, NY for his guidance on experimental designs in microbiology during my stay
and research at Cornell University. I acknowledge the contributions of Dr. Sohan Birla for his
guidance in the data analysis and technical writing. I am indebted to Mr. Christopher Derito,
Cornell University for teaching me cellular antioxidant analysis.
I thank Galina Mikhaylenko for her valuable suggestions and support in conducting my
experiments smoothly in the lab. I gratefully acknowledge the assistance of James Pan and
Matthew Tom, USDA-ARS, Albany, CA for their assistance and feedback during the extrusion
experiment. I thank Frank Younce, Wayne Dewitt, and Vince Himsl for their technical support
and assistance during my instrumentation. I thank my friend Gopal and senior colleague Ram,
who were highly supportive and stood by me through the thick and thin of my doctoral study.
Last but not least, I want to express my heartfelt thanks to my parents, wife Pinky, brothers
Uma and Titu, sister Gayatri for their understanding, encouragement and patience during my
research.
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EFFECT OF THERMAL PROCESSING ON THE PHENOLIC ANTIOXIDANTS OF
COLORED POTATOES
ABSTRACT
by Balunkeswar Nayak, Ph.D.
Washington State University
May 2011

Chair: Juming Tang
Foods with antioxidant capacity contribute health benefits and provide protection against
certain cancers, Alzheimer‘s dementia, and cardio-vascular diseases caused by oxidative
damage. Colored potatoes are a significant source of antioxidants from polyphenols, carotenoids,
and ascorbic acid. In this research, retention of total phenolics and antioxidant activity were
studied in fresh colored potatoes, and processed flakes were prepared as potential ingredients for
snack foods using freeze-drying, drum-drying and refractance window-drying. Extruded
products prepared from purple colored potatoes (‗Purple Majesty‘ cv) and yellow peas using a
twin-screw extruder were analyzed for the effect of extrusion cooking on their antioxidant
activity and anthocyanin level. Bioavailability of the phenolic antioxidants of extruded products
was analyzed using HepG2 liver cancer cells in a cellular antioxidant assay and compared with
unprocessed samples. Antioxidant potential of degradation products from purple potato
anthocyanins during high temperature processing and contribution to the total antioxidant
activity were measured using chemical assays (DPPH and ABTS). Thermal degradation kinetics
of anthocyanins prepared from ‗Purple Majesty‘ potatoes was conducted over a temperature
range of 100 – 150 °C. Dehydrated potato flakes showed no significant losses (P > 0.05) in total
antioxidant capacity (TAC) and total phenolics (TP) content, whereas 23 – 45% losses in total
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anthocyanins (TA) were observed during dehydration of potatoes. The quantity of TAC was
unchanged and the TP was largely retained (73 – 83%) in the extruded products prepared from
colored potatoes and yellow pea flours. Severe losses in TA (60 – 70%) of extruded products
were observed due to high temperature during extrusion cooking. The large bioavailability of the
extruded products was well supported by the ORAC antioxidant activity, total phenolics
(including free and bound fractions) and total flavonoids content irrespective of the degradation
of anthocyanins. The bioavailability in the extrudates could be attributed to the breakdown of the
conjugated phenolic antioxidants to their free forms, and formation of Maillard reaction products
with potential antioxidant activity. Thermal degradation in prepared anthocyanins followed a
first order reaction, but the degradation compounds had antioxidant potency contributing to the
TAC in the processed foods.
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TABLE OF CONTENT
ACKNOWLEDGMENTS ............................................................................................................. iii
ABSTRACT ................................................................................................................................... iv
LIST OF TABLES ....................................................................................................................... xiii
LIST OF FIGURES ..................................................................................................................... xvi

CHAPTER ONE
INTRODUCTION .......................................................................................................................... 1
1. SUMMARY OF RELATED STUDIES AND PROBLEM STATEMENTS............................. 1
2. OBJECTIVES ............................................................................................................................. 4
3. DISSERTATION OUTLINES ................................................................................................... 5
REFERENCES ............................................................................................................................... 9

CHAPTER TWO
EFFECT OF PROCESSING ON THE PHENOLIC ANTIOXIDANTS OF FRUITS,
VEGETABLES AND GRAINS – A REVIEW ............................................................................ 14
1. INTRODUCTION .................................................................................................................... 14
1.1. Antioxidants and Mechanism ............................................................................................ 17
1.2. Measurement of antioxidant activity ................................................................................. 19
2. PHENOLIC ANTIOXIDANTS OF FRUITS, VEGETABLE AND GRAIN .......................... 22
2.1. Effect of processing on phytochemicals ............................................................................ 27
2.1.1. Extraction .................................................................................................................... 29
2.1.2. Blanching .................................................................................................................... 31
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2.1.3. Cooking ....................................................................................................................... 33
2.1.4. Drying/Dehydration .................................................................................................... 37
2.1.5. Irradiation .................................................................................................................... 38
2.1.6. Extrusion ..................................................................................................................... 40
2.1.7. Non-thermal processing .............................................................................................. 41
2.1.8. Storage ........................................................................................................................ 43
2.1.9. Enzymatic/Chemical Oxidation .................................................................................. 47
3. ANTHOCYANINS ................................................................................................................... 49
3.1. Effect of processing on Anthocyanins ............................................................................... 56
3.1.1. Extraction .................................................................................................................... 56
3.1.2. Blanching .................................................................................................................... 57
3.1.3. Heating ........................................................................................................................ 59
3.1.4. Drying/Dehydration .................................................................................................... 61
3.1.5. CO treatment.............................................................................................................. 63
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3.1.6. Addition of external ingredients ................................................................................. 63
3.1.7. Non-thermal processing .............................................................................................. 65
3.1.8. Storage ........................................................................................................................ 66
3.2. Degradation mechanism and products ............................................................................... 69
3.3. Degradation kinetics of anthocyanins ................................................................................ 72
4. SUMMARY .............................................................................................................................. 80
REFERENCES ............................................................................................................................. 82

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CHAPTER THREE
COLORED POTATOES (SOLANUM TUBEROSUM L.) DRIED FOR ANTIOXIDANT-RICH
VALUE-ADDED FOODS.......................................................................................................... 116
1. INTRODUCTION .................................................................................................................. 116
2. MATERIALS AND METHODS ............................................................................................ 119
2.1. Raw Materials .................................................................................................................. 119
2.2. Production of potato flakes .............................................................................................. 119
2.2.1. Freeze-drying ............................................................................................................ 120
2.2.2. Drum-drying ............................................................................................................. 120
2.2.3. Refractance window-drying ..................................................................................... 120
2.3. Chemical Analysis ........................................................................................................... 121
2.3.1. Total antioxidant capacity ........................................................................................ 121
2.3.2. Total phenolics ......................................................................................................... 123
2.3.3. Total anthocyanins .................................................................................................... 123
2.4. Color determination ......................................................................................................... 125
2.5. Statistical analysis ............................................................................................................ 125
3. RESULTS AND DISCUSSION ............................................................................................. 126
3.1. Moisture content, total antioxidant capacity (TAC), total phenolics (TP) and total
anthocyanins (TA) in raw potatoes ......................................................................................... 126
3.2. Effects of blanching on TAC, TP and TA ....................................................................... 127
3.3 Total antioxidant capacity, total phenolics and total anthocyanins in dehydrated potato
flakes ....................................................................................................................................... 130
3.4. Correlation between TP and TAC.................................................................................... 132
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3.5. Color in raw cultivars and dehydrated flakes .................................................................. 133
4. CONCLUSION ....................................................................................................................... 135
ACKNOWLEDGEMENTS ........................................................................................................ 136
REFERENCES ........................................................................................................................... 137

CHAPTER FOUR
EFFECT OF EXTRUSION ON THE ANTIOXIDANT CAPACITY AND COLOR
ATTRIBUTES OF EXPANDED EXTRUDATES PREPARED FROM PURPLE POTATO
AND YELLOW PEA FLOUR MIXES ...................................................................................... 142
1. INTRODUCTION .................................................................................................................. 143
2. MATERIALS AND METHODS ............................................................................................ 144
2.1. Materials .......................................................................................................................... 144
2.1.1. Production of potato flours ....................................................................................... 145
2.1.2. Sample preparation ................................................................................................... 145
2.1.3. Extrusion conditions ................................................................................................. 146
2.1.4. Experimental design.................................................................................................. 147
2.1.5. Determination of Expansion ratio ............................................................................. 147
2.1.6. Moisture content determination ................................................................................ 148
2.1.7. Pasting profile of potato flours ................................................................................. 148
2.1.8. Color evaluation ........................................................................................................ 148
2.2. Chemical Analyses........................................................................................................... 150
2.2.1. Total antioxidant capacity ......................................................................................... 150
2.2.2. Total phenolics ......................................................................................................... 151
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2.2.3. Total anthocyanins ................................................................................................... 152
2.2.4. Browning Index ....................................................................................................... 153
2.3. Statistical analysis ............................................................................................................ 153
3. RESULTS AND DISCUSSION ............................................................................................. 154
3.1. Expansion ratio ............................................................................................................... 154
3.2. Pasting behavior of potato flours ..................................................................................... 156
3.3. Color attributes................................................................................................................. 157
3.4. Total antioxidant capacity ................................................................................................ 159
3.5. Total phenolics ................................................................................................................. 162
3.6. Total anthocyanins ........................................................................................................... 164
3.7. Browning Index .............................................................................................................. 166
3.8. Correlation analyses ......................................................................................................... 167
4. CONCLUSIONS..................................................................................................................... 167
ACKNOWLEDGEMENTS ........................................................................................................ 168
REFERENCES ........................................................................................................................... 169

CHAPTER FIVE
BIOAVAILABILITY OF ANTIOXIDANTS IN EXTRUDED PRODUCTS PREPARED FROM
PURPLE POTATO AND DRY PEA FLOURS ......................................................................... 175
1. INTRODUCTION .................................................................................................................. 176
2. MATERIALS AND METHODS ............................................................................................ 178
2.1. Chemicals and Reagents .................................................................................................. 178
2.2. Preparation of Samples .................................................................................................... 178
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