Determination of antioxidant capacity in corn germ, wheat germ and wheat bran using solvent and

79 Pages·2017·0.62 MB·English

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LSU Master's Theses Graduate School
2006
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David Swenson Oufnac
Louisiana State University and Agricultural and Mechanical College
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DETERMINATION OF ANTIOXIDANT CAPACITY IN CORN
GERM, WHEAT GERM AND WHEAT BRAN USING
SOLVENT AND MICROWAVE-ASSISTED SOLVENT
EXTRACTION

A Thesis

Submitted to the Graduate Faculty of the
Louisiana State University and
Agricultural and Mechanical College
in partial fulfillment of the
requirements for the degree of
Master of Science

In

The Department of Food Science

By
David Swenson Oufnac
B.S. Culinary Arts, Nicholls State University, 1999
December, 2006
DEDICATION
This thesis is dedicated to my loving parents, Murphy L. Oufnac Jr. and Marilyn
B. Oufnac, whose sacrifices and support throughout the years have inspired me to be a
better person in all aspects of life. Your selflessness and beautiful nature remind me
every day how proud I am to be your son. Thank you both for all you have done and for
what you continue to do. I love you very much.
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ACKNOWLEDGMENTS
I wish to convey my deepest gratitude to my major professor and advisor, Dr.
Zhimin Xu, for his guidance and patience during my three years working towards a
Master of Science degree from Louisiana State University. Working with Dr. Xu has
been a treasured experience for me while in the Department of Food Science. It has been
a pleasure and I feel much more confident in my abilities having Dr. Xu’s encouragement
and support.
I would also like to thank Dr. Ting Sun for all her help and support during my last
year of experiments. Also, a special thanks to my committee members, Dr. Witoon
Prinyawiwatkul and Dr. Christina Sabliov, for their valuable time as well as the use of
their labs. I would also like to thank my fellow students, namely Sandeep Bhale, Karen
Garcia, Amrish Chawla, Rishipal Bansode and Evi Menelaou for making my experience
at LSU so uniquely memorable. Several people who have had a colossal influence on my
life deserve thanks as well, so I would like to express my gratitude to Dr. Jerald Chesser,
Dr. Robert Harrington, Mr. And Mrs. Clarence Landry and Mitchell Rotolo.
My most sincere appreciation goes out to my parents who have disciplined and
nurtured me throughout life to give me the strength and tools to achieving any goals I
may set for myself. A special thanks goes to my loving sister and dear brother who are a
constant reminder that there are people who still inspire my world.
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TABLE OF CONTENTS

DEDICATION...................................................................................................................ii

ACKNOWLEDGMENTS...............................................................................................iii

LIST OF TABLES..........................................................................................................vii

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

ABSTRACT.......................................................................................................................x

CHAPTER 1. INTRODUCTION....................................................................................1

CHAPTER 2. LITERATURE REVIEW........................................................................4
2.1 Introduction...............................................................................................................4
2.2 Antioxidants and Free Radicals................................................................................6
2.2.1 Alpha Tocopherol (Vitamin E)..........................................................................9
2.2.2 Ascorbic Acid (Vitamin C)..............................................................................10
2.2.3 Beta Carotene...................................................................................................10
2.3 Extraction Methods.................................................................................................12
2.4 Antioxidant Capacity Assays..................................................................................13
2.4.1 Trolox Equivalent Antioxidant Capacity (TEAC) Assay................................14
2.4.2 DPPH (2,2-Diphenyl-1-picrylhydrazyl) Assay................................................16
2.4.3. Folin-Ciocalteau or Total Phenolics Assay.....................................................17

CHAPTER 3. EXTRACTION OF ANTIOXIDANTS FROM WHEAT BRAN
USING CONVENTIONAL AND MICROWAVE-ASSISTED METHODS............19
3.1 Introduction.............................................................................................................19
3.2 Materials and Methods............................................................................................22
3.2.1 Chemicals and Materials..................................................................................22
3.2.2 Conventional Solvent Extraction.....................................................................22
3.2.3 Microwave-Assisted Solvent Extraction..........................................................23
3.2.4 Determination of Total Phenolic Compound Content.....................................24
3.2.5 Determination of Antioxidant Activity Using DPPH Radical Scavenging
Method......................................................................................................................24
3.2.6 Statistical Analysis...........................................................................................25
3.3 Results and Discussion...........................................................................................25
3.3.1 Extraction Yields of Wheat Bran Extracted by Conventional Solvent and
Microwave-assisted Solvent Extractions..................................................................25
3.3.2 Total Phenolic Compound of Wheat Bran Extracted by Different Solvent and
Microwave-assisted Solvent Extractions..................................................................27
3.3.3 Free Radical Quenching Capability of Wheat Bran Extracts by Different
Solvent and Microwave-assisted Solvent Extractions..............................................29
3.4 Conclusions.............................................................................................................30

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CHAPTER 4. EXTRACTION OF ANTIOXIDANTS FROM CORN GERM USING
CONVENTIONAL AND MICROWAVE-ASSISTED METHODS..........................32
4.1 Introduction.............................................................................................................32
4.2 Materials and Methods............................................................................................34
4.2.1 Chemicals and Materials..................................................................................34
4.2.2 Conventional Solvent Extraction.....................................................................34
4.2.3 Microwave-Assisted Solvent Extraction..........................................................35
4.2.4 Determination of Total Phenolic Compound Content.....................................35
4.2.5 Determination of Antioxidant Activity Using DPPH Radical Scavenging
Method......................................................................................................................36
4.2.6 Statistical Analysis...........................................................................................37
4.3 Results and Discussion...........................................................................................37
4.3.1 Extraction Yields of Corn Germ Extracted by Conventional Solvent and
Microwave-assisted Solvent Extractions..................................................................37
4.3.2 Total Phenolic Compound of Corn Germ Extracted by Different Solvent and
Microwave-assisted Solvent Extractions..................................................................38
4.3.3 Free Radical Quenching Capability of Corn Germ Extracts by Different
Solvent and Microwave-assisted Solvent Extractions..............................................40
4.4 Conclusions.............................................................................................................42

CHAPTER 5. EXTRACTION OF ANTIOXIDANTS FROM WHEAT GERM
USING CONVENTIONAL AND MICROWAVE-ASSISTED METHODS............43
5.1 Introduction.............................................................................................................43
5.2 Materials and Methods............................................................................................45
5.2.1 Chemicals and Materials..................................................................................45
5.2.2 Conventional Solvent Extraction.....................................................................45
5.2.3 Microwave-Assisted Solvent Extraction..........................................................46
5.2.4 Determination of Total Phenolic Compound Content.....................................47
5.2.5 Determination of Antioxidant Activity Using DPPH Radical Scavenging
Method......................................................................................................................47
5.2.6 Statistical Analysis...........................................................................................48
5.3 Results and Discussion...........................................................................................48
5.3.1 Extraction Yields of Wheat Germ Extracted by Conventional Solvent and
Microwave-assisted Solvent Extractions..................................................................48
5.3.2 Total Phenolic Compound of Wheat Germ Extracted by Different Solvent and
Microwave-assisted Solvent Extraction....................................................................50
5.3.3 Free Radical Quenching Capability of Wheat Germ Extracts by Different
Solvent and Microwave-assisted Solvent Extraction................................................51
5.4 Conclusions.............................................................................................................53

CHAPTER 6: SUMMARY AND CONCLUSION......................................................54

REFERENCES................................................................................................................56

APPENDIX A. YIELD RESULTS................................................................................64

APPENDIX B. PHENOLICS RESULTS.....................................................................65
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APPENDIX C. DPPH RESULTS..................................................................................66

APPENDIX D. SAS CODE............................................................................................67

VITA.................................................................................................................................68

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LIST OF TABLES
Table 1. Extraction yield results (%)………………………………………………….....64

Table 2. Capabilities of scavenging DPPH free radicals (Trolox Equivalent nmol/g)…..65

Table 3. Total phenolic compound contents (Catechin Equivalent μg/g)……………….66

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LIST OF FIGURES
Figure 1. Free Radical Molecule…………………………………………………………. 5

Figure 2. Chemical structures of synthetic antioxidants (a) butylated hydroxyanisol
(BHA), and (b) butylated hydroxytoluene (BHT)………………………………………...6

Figure 3. Chemical structures of phenolic acids (a) Vanillic Acid, (b) Ferulic Acid, (c)
Syringic Acid, and (d) p-Coumaric Acid………………………………………………….7

Figure 4. Chemical structure of Vitamin E………………………………………………..9

Figure 5. Chemical Structure of Vitamin C...……………………………………………10

Figure 6. Chemical structures of carotenoids and tocopherols. -Carotene (I), astaxanthin
(II), canthaxanthin (III), zeaxanthin (IV), lutein (V), -cryptoxanthin (VI), lycopene
(VII), bixin (VIII), -tocopherol (IX) and -tocopherol (X). …………………………...11

Figure 7. Chemical structure of ABTS•+………………………………………………...15

Figure 8. Chemical structure of DPPH…………………………………………………..16

Figure 9. Phenolic compounds……………………………………………..…………….18

Figure 10. Diagram of a wheat kernel…………………………………………………...20

Figure 11. Extraction yield (% of fresh wheat bran) obtained by conventional solvent
extraction using different solvents and microwave-assisted solvent extraction (with
methanol) at different temperatures……………………………………………………...26

Figure 12. Total phenolic compound contents (Catechin Equivalent μg /g fresh wheat
bran) from wheat bran extracted by conventional solvent extraction using different
solvents and microwave-assisted solvent extraction (with methanol) at different
temperatures……………………………………………………………………………...28

Figure 13. Capabilities of scavenging DPPH free radicals (Trolox Equivalent nmol /g
fresh wheat bran) from wheat bran extracted by conventional solvent extraction using
different solvents and microwave-assisted solvent extraction (with methanol) at different
temperatures……………………………………………………………………………...30

Figure 14. Chemical structure of Linoleic Acid…………………………………………32

Figure 15. Extraction yield (% of fresh corn germ) obtained by conventional solvent
extraction using different solvents and microwave-assisted solvent extraction (with
methanol) at different temperatures……………………………………………………...38

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Figure 16. Total phenolic compound contents (Catechin Equivalent μg /g fresh corn
germ) from corn germ extracted by conventional solvent extraction using different
solvents and microwave-assisted solvent extraction (with methanol) at different
temperatures……………………………………………………………………………...39

Figure 17. Capabilities of scavenging DPPH free radicals (Trolox Equivalent nmol /g
fresh corn germ) from corn germ extracted by conventional solvent extraction using
different solvents and microwave-assisted solvent extraction (with methanol) at different
temperatures……………………………………………………………………………...41

Figure 18. Extraction yield (% of fresh wheat germ) obtained by conventional solvent
extractions using different solvents and microwave-assisted solvent extraction (with
methanol) at different temperatures……………………………………………………...49

Figure 19. Total phenolic compound contents (Catechin Equivalent μg /g fresh wheat
germ) from wheat germ extracted by conventional solvent extraction using different
solvents and microwave-assisted solvent extraction (with methanol) at different
temperatures……………………………………………………………………………..51

Figure 20. Capabilities of scavenging DPPH free radicals (Trolox Equivalent nmol /g
fresh wheat germ) from wheat germ extracted by conventional solvent extractions using
different solvents and microwave-assisted solvent extraction (with methanol) at different
temperatures……………………………………………………………………………...53

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