ANTIMICROBIAL AND ANTIOXIDANT PROPERTIES OF CHITOSAN by PALLAVI CHHABRA ...

82 Pages·2004·0.51 MB·English

ANTIMICROBIAL AND ANTIOXIDANT PROPERTIES OF CHITOSAN

by

PALLAVI CHHABRA

(Under the direction of Dr. Yao-wen Huang)

ABSTRACT
The effect of chitosan as coatings for evaluating the antimicrobial and antioxidant effects
on raw oysters was evaluated over a 12 to 15-day storage at 4 ºC. Four chitosan
concentrations were prepared: 0.0, 0.5, 1.0 and 2.0%.Uncoated samples served as the
control. Samples were then subjected to microbial and chemical examination. The growth
of Staphylococcus aureus cells was inhibited by all treatments on day 15, After pre-
enrichment. Thus, the effectiveness of chitosan against S. aureus was not very clear when
the pre-enrichment step was included. Similarly, the growth inhibition of S. aureus by
chitosan was studied without pre-enrichment of samples with the storage time reduced to
12 days. Cells were most sensitive to chitosan at 2.0% concentration, followed by 0.5%
and 1.0%. Hence, 2.0% chitosan emerged as the best treatment for the inhibition and
inactivation of S. aureus in raw oysters. Raw oysters coated with different levels of
chitosan showed no increase in the 2 – thiobarbituric acid reactive substances (TBARS)
throughout the entire period of storage. Also, no significant differences were found
among the various treatments. Thus, chitosan can be used as an antimicrobial agent but
the antioxidant effect of chitosan should be measured by some other method than the
TBARS test.

INDEX WORDS: Chitosan, Staphylococcus aureus, 2 – thiobarbituric acid reactive
substances test, Oysters
ANTIMICROBIAL AND ANTIOXIDANT PROPERTIES OF CHITOSAN

by

PALLAVI CHHABRA

B.S., S.I.E.S. College of Arts, Science and Commerce, Mumbai, India, 1999

Post-Graduate Diploma, S.N.D.T. University, Mumbai, India, 2001

A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial
Fulfillment of the Requirements of the Degree

MASTER OF SCIENCE

ATHENS, GEORGIA

2004
© 2004

Pallavi Chhabra

All Rights Reserved
ANTIMICROBIAL AND ANTIOXIDANT PROPERTIES OF CHITOSAN

by

PALLAVI CHHABRA

Major Professor: Yao-wen Huang
Committee: Joseph Frank
Manjeet Chinnan
Keith Gates

Electronic Version Approved:

Maureen Grasso
Dean of the Graduate School
The University of Georgia
December 2004
iv
DEDICATION

I am dedicating this thesis to God who has helped me in every phase of my life.
Next, I want to dedicate this to my nephew, Sanidhya Pandey. I would also like to
dedicate this work to my Mom and Dad for their support and encouragement and for
providing me with the opportunity to study in the United States of America. I cannot
forget my brother, Amit Chhabra, whose very inspiration and encouragement made this
work possible.
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ACKNOWLEDGEMENTS
First and foremost, I would like to thank my major Professor Dr. Yao-wen Huang,
whose continuous support, patience, direction and tremendous effort made this work
possible. Dr. Huang, you believed in me the very first time I met you in August 2002 and
continued to help me all through my M.S. degree. I have learnt an incredible amount of
Food Science from you. You are simply great and I wish to take this opportunity to
express my heartfelt gratitude and respect to you.
Next, I would like to thank Dr. Joseph F. Frank, Dr. Manjeet Chinnan and Dr.
Keith Gates, for being on my Committee and for always being there for me. Thanks to
Dr. Frank for allowing me to conduct experiments in his lab.
One person whose immense effort actually made my work progress and reach
completion is Dr. Revis Chmielewski. Revis, it’s really hard to find someone as kind and
helpful like you. You were there for me at every step of my research. Your positive
attitude, outstanding knowledge, the precision in explaining things, extreme patience and
love made my work so simple. Thank you so much for all your help.
Another person without whom this work would have not been completed is Ruth
Ann Morrow. Thanks Ruth Ann for your goodness, patience and help.
I would also like to acknowledge Dr. Rakesh Singh for his advice, help, support
and wishes. Dr. Singh, you are one of the most wonderful and successful persons I have
ever met.
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I would like to extend my sincere gratitude towards my lab mates Wanwimol
Klaypradit and Hsiao Yun Chu. Thanks for always answering my queries and for being
so nice and warm towards me.
I would also like to thank all the people in Dr. Frank’s lab: Carl E. Ruiz, Arpan
Bhagat, Linda Genzlinger, Mustafa Simmons and James Folsom for their help during my
thesis.
I would also like to thank some people who became my very good friends during
the course of my study and helped me at different times. Special thanks to my friends at
the Food Science Department: Stephen Enyam Lumor, Paul Jesse Milly and Mark
Jarrard.
Last but not the least I want to thank some very special people in my life who are
like my family away from home. Thanks Anand for your love, affection and support. I
want to especially thank my friend Rohit Aggarwal for being an idol for me and for his
immense help and support during my thesis. I would also like to extend a special thank
you to my friend Suhail Halai for all his help during my experiments.
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TABLE OF CONTENTS

Page
ACKNOWLEDGEMENTS ………………...……………………………………….……v
LIST OF TABLES …...…………………………………………………….……………..x
LIST OF FIGURES ……...………………………………………………………………xi
CHAPTER
1 INTRODUCTION AND LITERATURE REVIEW
1.1 Purpose of the Study ………...……………………………………………1
1.2 Chitin and Chitosan ……………………………………………...………..2
1.3 Properties of Chitosan ………………………………………….......……..3
1.4 Chitosan as an Edible Film/Coating …………...…………………………5
1.5 Antimicrobial Properties of Chitosan and its Derivatives ……...………...6
1.6 Mode of Action of Chitosan as an Antimicrobial Agent ……………..…13
1.7 Antioxidant Properties of Chitosan and its Derivatives ……...………….15
1.8 2-Thiobarbituric Acid Reactive Substances (TBARS) Test …...……..…17
1.9 Seafoods …...…………………………………………………………….18
1.10 Oysters and their Filter Feeding Mechanism …..…...………………….18
1.11 Spoilage in Oysters ………...……………………………….………….19
1.12 Raw Shellfish Consumption and Related Issues ……………...………..19
1.13 Pathogenic Bacteria …….…...…………………………………………20
1.14 Vibrio vulnificus ……………...………………………………………...21
1.15 Staphylococcus aureus ……………...………………………………….24
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1.16 Salmonella typhimurium ………………...……………………………..26
1.17 Psychrotrophic organisms ……...……………………………………....28
1.18 References ……...………………………………………………………29
1 THE FATE OF CHITOSAN ON STAPHYLOCOCCUS AUREUS IN RAW
OYSTERS AS AFFECTED BY CHITOSAN
Abstract …...……………...…………………………………………………………42
Introduction ………...……………………………………………………………….43
Materials and Methods ………………...……………………………………………45
Results and Discussion ……...……………………………………………………...49
Conclusions ………...…………………………………………………………...…..51
References ……………………...…………………………………………………...53
2 ANTIOXIDANT EFFECT OF CHITOSAN ON RAW OYSTERS AS MEASURED
BY THE 2-THIOBARBITURIC ACID REACTIVE SUBSTANCES (TBARS)
TEST
Abstract ………………………...…………………………………………………...56
Introduction ………...……………………………………………………………….57
Materials and Methods ……………...………………………………………………59
Results and Discussion ……...……………………………………………………...61
Conclusions …...…………………………………………………………………….62
References …………...……………………………………………………………...64
3 SUMMARY AND CONCLUSIONS ……...……………………………………….66
4 APPENDIX …………………...…………………………………………………….68
ix

LIST OF TABLES

Page

TABLE 2.1 - Effect of various levels of chitosan on the growth of S. aureus (log cfu/ml
of homogenate) on raw oysters stored at 4 °C for 15 days (with the pre-enrichment
step)…………………………………………………………………………...………….52
TABLE 2.2 - Effect of various levels of chitosan on the growth of S. aureus (log cfu/ml
of homogenate) on raw oysters stored at 4 °C for 12 days (without the pre-enrichment
step) ……………………………………………………………………………...………52
Table 3.1 – TBARS values (expressed as malonaldehyde µM/kg oyster) of chitosan-
coated oysters during a 15 – day storage at 4 °C for 15 days…………………………....63