PHYTOCHEMICAL, ANTIOXIDANT, AND STORAGE STABILITY OF THERMALLY PROCESSED ...

79 Pages·2005·0.33 MB·English

PHYTOCHEMICAL, ANTIOXIDANT, AND STORAGE STABILITY OF
THERMALLY PROCESSED GUAVA (Psidium guajava) AND GUAVA JUICE
BLENDS

By

LANIER FENDER

A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2005
Copyright 2005

by

LANIER FENDER
ACKNOWLEDGMENTS
I would like to thank my major advisor, Dr. Stephen Talcott, for giving me the
opportunity to further my education, and especially for all of his help, suggestions,
guidance and wisdom throughout my graduate studies. I also thank my advising
committee members, Dr. Charles Sims and Dr. Donald Huber, for their time and
assistance with my research.
I would also like to say thank you to my past and present lab and lunchmates:
Chris, David, Flor, Jorge, Joon, Kim, Kristine, Lisbeth, Maria, Sara, and Lorenzo for
helping me in the lab and for helping to make graduate school an enjoyable experience.
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TABLE OF CONTENTS

page
ACKNOWLEDGMENTS.................................................................................................iii
LIST OF TABLES.............................................................................................................vi
LIST OF FIGURES..........................................................................................................vii
ABSTRACT.......................................................................................................................ix
CHAPTER
1 INTRODUCTION.........................................................................................................1
2 LITERATURE REVIEW..............................................................................................3
Guava Production and Market Potential.......................................................................3
Thermal Processing of Guava.......................................................................................4
Guava Antioxidants......................................................................................................5
Polyphenolics........................................................................................................6
Phenolic thermal stability...............................................................................9
Ascorbic Acid........................................................................................................9
Carotenoids/Lycopene.........................................................................................11
Anthocyanins..............................................................................................................13
3 EFFECTS OF THERMAL PROCESSING AND STORAGE ON THE
PHYTOCHEMICALS AND ANTIOXIDANTS IN GUAVA NECTAR..................17
Materials And Methods..............................................................................................18
Materials And Processing....................................................................................18
Physicochemical Analysis...................................................................................19
Vitamin C.....................................................................................................19
Total soluble phenolics.................................................................................19
Antioxidant activity......................................................................................20
Lycopene......................................................................................................20
Statistical Analysis..............................................................................................21
Results And Discussion..............................................................................................21
Effects On L-Ascorbic Acid................................................................................21
Effects On Lycopene...........................................................................................24
Effects On Polyphenolics....................................................................................26
iv
Effects On Antioxidant Activity..........................................................................27
Conclusions.........................................................................................................31
4 THE EFFECTS OF ANTHOCYANIN-CONTAINING JUICE BLENDS ON THE
PHYSIOCHEMICAL AND ANTIOXIDANT CAPACITY OF GUAVA JUICE....32
Introduction.................................................................................................................32
Materials and Methods...............................................................................................34
Materials And Processing....................................................................................34
Chemical Analysis...............................................................................................35
L-Ascorbic Acid..................................................................................................35
Phenolics by HPLC......................................................................................35
Total anthocyanins.......................................................................................36
Percent monomeric and polymeric anthocyaninins.....................................36
Statistical Analysis..............................................................................................36
Results And Discussion..............................................................................................37
Effects On Anthocyanins.....................................................................................37
Guava juice blends.......................................................................................37
synthetic L-ascorbic acid models.................................................................42
anthocyanin controls....................................................................................47
Anthocyanin Degradation Kinetics.....................................................................48
Effect On Naturally Occurring And Fortified L-Ascorbic Acid.........................50
Effects On Antioxidant Activity..........................................................................51
Effects On Polyphenolics....................................................................................57
Conclusions.........................................................................................................59
5 SUMMARY AND CONCLUSIONS...........................................................................61
LIST OF REFERENCES...................................................................................................63
BIOGRAPHICAL SKETCH.............................................................................................69

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LIST OF TABLES
Table page

3-1. Correlations (R2) of ORAC vs. L-ascorbic acid, total soluble phenolics, and
lycopene during storage for 28 days at 4 and 25oC..................................................31
4-1. Effects of storage temperature and L-ascorbic acid on first order regression, rate,
and half life of total anthocyanins. Different letters represent differences
between sample types with or without L-ascorbic acid...........................................48
4-2. Effects of storage temperature and L-ascorbic acid on first order regression, rate,
and half life of total anthocyanins. Different letters represent differences
between sample types with or without L-ascorbic acid. N/A = not applicable due
to high stability or fluctuation in the data................................................................51
4-3. Tentative identification of guava juice polyphenolics, measured by HPLC/PDA....58
4-4. Percent of initial polyphenolics after four weeks of storage at 6 and 25 oC..............59

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LIST OF FIGURES
Figure page

3-1. Effects of processing and storage on L-ascorbic acid. Bars represent the standard
error of the mean, n=3..............................................................................................23
3-2. Effects of processing and storage on lycopene. Bars represent the standard error
of the mean, n=3.......................................................................................................25
3-3. Effects of processing and storage on total soluble phenolics. Bars represent the
standard error of the mean, n=3...............................................................................28
3-4. Percent initial of total soluble phenolics after water extraction and dilutions. J2:
100% guava juice, J3: puree from J2, diluted 1:1 with water, J4: puree from J3,
diluted 1:1 with water, J5: puree from J4, diluted 1:1 with water, J6: puree from
J4, heated for 1 minute at 100oC. Bars represent the standard error of the mean,
n=3............................................................................................................................29
3-5. Effects of processing and storage on antioxidant activity. Bars represent the
standard error of the mean, n=3...............................................................................30
4-1. Percent initial of total anthocyanins stored at 25 o C for 28 days. Control is the
unpasteurized juice. Bars represent standard error of the mean, n=3......................38
4-2. Percent initial of total anthocyanins stored at 6oC for 28 days. Control is the
unpasteurized juice. Bars represent standard error of the mean, n=3......................39
4-3. Percent initial of total anthocyanins stored at 25oC for 28 days. Control isthe
unpasteurized juice. Bars represent standard error of the mean, n=3......................40
4-4. Percent initial of total anthocyanins stored at 6oC for 28 days. Control is the
unpasteurized juice. Bars represent standard error of the mean, n=3......................41
4-5. Percent polymeric anthocyanins of acai based samples stored at 25oC. Bars
represent standard error of the mean, n=3................................................................44
4-6. Percent polymeric anthocyanins of acai based samples stored at 6oC. Bars
represent standard error of the mean, n=3................................................................44
4-7. Percent polymeric anthocyanins of black currant based samples stored at 25oC.
Bars represent standard error of the mean, n=3.......................................................45
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4-8. Percent polymeric anthocyanins of black currant based samples stored at 6oC.
Bars represent standard error of the mean, n=3.......................................................45
4-9. Percent initial of L-ascorbic acid in acai based samples stored at 25oC. Control is
the unpasteurized juice. Bars represent standard error of the mean, n=3.................52
4-10. Percent initial of L-ascorbic acid in acai based samples stored at 6oC. Control is
the unpasteurized juice. Bars represent standard error of the mean, n=3.................53
4-11. Percent initial of L-ascorbic acid in black currant based samples stored at 25oC.
Control is the unpasteurized juice. Bars represent standard error of the mean,
n=3............................................................................................................................53
4-12. Percent initial of L-ascorbic acid in black currant based samples stored at 6oC.
Control is the unpasteurized juice. Bars represent standard error of the mean,
n=3............................................................................................................................54
4-13. Percent initial of antioxidant activity in acai based samples stored at 25oC.
Control is the unpasteurized juice. Bars represent standard error of the mean,
n=3............................................................................................................................55
4-14. Percent initial of antioxidant activity in acai based samples stored at 6oC.
Control is the unpasteurized juice. Bars represent standard error of the mean,
n=3............................................................................................................................56
4-15. Percent initial of antioxidant activity in black currant samples stored at 25oC.
Control is the unpasteurized juice. Bars represent standard error of the mean,
n=3............................................................................................................................56
4-16. Percent initial of antioxidant activity in black currant samples stored at 6oC.
Control is the unpasteurized juice. Bars represent standard error of the mean,
n=3............................................................................................................................57
4-17. HPLC chromatogram (at 280nm) of polyphenolic compounds found in guava
juice. 1) gallic acid 2) (+)-catechin 3) ellagic acid 4) ellagic acid derivative 5)
unknown characteristic guava polyphenolic............................................................58

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Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

PHYTOCHEMICAL AND ANTIOXIDANT STABILITY OF THERMALLY
PROCESSED GUAVA (Psidium guajava) AND GUAVA JUICE BLENDS
By
Lanier Fender
December 2005
Chair: Stephen T. Talcott
Major Department: Food Science and Human Nutrition
Due to limited availability of fresh guava, most fruit destined for US markets is
processed into juice, puree, jams, jellies, and syrup, and juice blends. Therefore, it is
pertinent to study the effects of pasteurization and storage conditions on the health and
quality aspects of guava juices and juice blends. The objectives of this study were to
assess the thermal stability and shelf life properties of phytochemicals antioxidants in
guava nectar and to determine the juice blending/color fortification potential of guava
juice with an anthocyanin containing source. Guava nectar was pasteurized at two
different time/temperatures and stored in order to determine the stability of antioxidant
phytochemicals and shelf life properties. Clarified guava juice was blended with
anthocyanin containing juices and isolates (açai and black currant), pasteurized and then
stored in order to determine the stability of antioxidant phytochemicals and shelf life
properties.
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For the initial study, guava nectar was pasteurized at 82oC for 20 seconds (Process
1) and 87oC for 90 seconds (Process 2) and stored at 4 and 25oC. Pasteurization at 82oC
for 20 seconds resulted in no significant changes in L-ascorbic acid, lycopene, or total
antioxidant activity, while total soluble phenolics increased 77%. Pasteurization at 87oC
for 90 seconds resulted in no significant differences in L-ascorbic acid and total
antioxidant activity, while lycopene decreased 40% and total soluble phenolics increased
72% as a result of pasteurization. After 42 days of storage at 4oC, L-ascorbic acid was
completely degraded in both Process 1 and 2 nectars, lycopene decreased 40% in Process
1 and did not significantly decrease in Process 2, and total soluble phenolics and
antioxidant activity were not significantly different for either process. After 42 days of
storage at 25oC, L-ascorbic acid was completely degraded in both Process 1 and 2
nectars, lycopene decreased 40 % in Process 1 and did not decrease in Process 2, while
total soluble phenolics decreased 28 and 17% for Process 1 and 2 respectively, and total
antioxidant activity decreased 47 and 39% respectively.
Clarified guava juice was blended with açai and black currant juice and C18
isolates pasteurized and stored for 28 days. Storage at 6oC significantly protected
antioxidant phytochemicals in the guava juice blends, compared to those stored at 25oC.
Guava juice blends stored at 6oC retained between 64-83% of their total anthocyanins,
while those stored at 25oC retained between 39-74%. Overall, C18 isolates + guava juice
were more stable than the anthocyanin juice + guava juice treatments, with Açai C18 +
guava juice being the most stable in terms of total anthocyanins. All L-ascorbic acid was
lost after 28 days at 25oC, while juices held at 4oC retained between 20-65% of their
initial L-ascorbic acid.
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