Quality Improvement of Soymilk Processed from Two Soybean
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QUALITY IMPROVEMENT OF SOYMILK PROCESSED FROM TWO SOYBEAN VARIETIES A Thesis Submitted to the Graduate Faculty of the North Dakota State University of Agriculture and Applied Science By Yan Zhang In Partial Fulfillment for the Degree of MASTER OF SCIENCE Major Department: Cereal and Food Science August 2012 Fargo, North Dakota North Dakota State University Graduate School Title QUALITY IMPROVEMENT of SOYMILK PROCESSED from TWO SOYBEAN VARIETIES By YAN ZHANG The Supervisory Committee certifies that this disquisition complies with North Dakota State University‟s regulations and meets the accepted standards for the degree of MASTER OF SCIENCE SUPERVISORY COMMITTEE: Sam Chang Chair Khlil Khan Senay Simsek Dennis Wisenborn Approved: 7/17/2012 Deland Meyers Date Department Chair ABSTRACT Five soymilk characteristics were investigated as affected by different grinding, heating, extraction methods and varieties. The five characteristics are (1) protein and solid recovery, (2) trypsin inhibitor activity, (3) antioxidant compounds and antioxidant capacity, (4) soy odor, and (5) isoflavone content and profile. The two varieties were Prosoy and black soybeans. The results show that significant differences existed among the three grinding methods (ambient grinding, cold grinding, and hot grinding). Ambient grinding gave the best protein and solid recoveries. Hot grinding showed the best results for the other four parameters. Cold grinding gave the poorest performance, with the exception of the odor profile. The three heating methods (traditional stove cooking, one-phase UHT, two-phase UHT) also resulted in significant differences. In many cases, the effects of heating methods were closely related to grinding methods and varieties. The two varieties behaved differently during processing. For both varieties, extraction methods showed significant differences. iii ACKNOWLEDGEMENTS I want to express my deepest appreciation to my advisor, Dr. K.C. Sam Chang for his valuable and patient guidance throughout my project. Without his help, I could not complete my master‟s study. I would like to thank my committee members, Dr. Khalil Khan, Dr. Dennis Wiesenborn, and Dr. Senay Simsek for their constructive criticism and suggestions. Sincere thanks must go to Dr. Zhisheng Liu for his dedicated technical support and preparation of many samples. I also want to express my appreciation to Mrs. Gloria Nygard for her kind support and help with laboratory procedures and equipment usage. I am grateful to Dr. Deland Meyers for his encouragement and support. Special thanks go to Charlene Kuss and Cindy Selstedt for their support during my whole graduate study. I want to thank everyone in my group, Dr. Yanping Zou, Dr. Yingying Tan, Dr. Fanrong Yao, Yiqun Ou, Jianteng Xu, and Keerthi for their help and good advice. I would like to thank North Dakota Soybean Council and USDA-NIFA (CSREES) National Research Initiative Program for providing the funding for this research. Finally, special thanks should be given to my wife, Hui Zhang for her whole-hearted support and love. iv TABLE OF CONTENTS ABSTRACT ............................................................................................................................. iii ACKNOWLEDGEMENTS ...................................................................................................... iv LIST OF TABLES .................................................................................................................... vi LIST OF FIGURES ............................................................................................................... viii INTRODUCTION ..................................................................................................................... 1 LITERATURE REVIEW .......................................................................................................... 3 CHAPTER 1. YIELD, SOLID AND PROTEIN RECOVERY OF SOYMILK AS AFFECTED BY EXTRACTION AND GRINDING METHODS ......................................... 16 CHAPTER 2. TRYPSIN INHIBITORS OF SOYMILK AS AFFECTED BY DIFFERENT GRINDING AND HEATING METHODS ............................................................................. 33 CHAPTER 3. PHENOLIC COMPOUNDS AND ANTIOXIDANT CAPACITY OF SOYMILK AS AFFECTED BY DIFFERENT GRINDING AND HEATING METHODS . 54 CHAPTER 4. SELECTED ODOR COMPOUNDS OF SOYMILK AS AFFECTED BY DIFFERENT GRINDING AND HEATING METHODS ...................................................... 76 CHAPTER 5. ISOFLAVONE PROFILE AND CONTENT OF SOYMILK AS AFFECTED BY DIFFERENT GRINDING AND HEATING METHODS ......................... 101 OVERALL CONCLUSIONS ................................................................................................ 128 FUTURE RESEARCH .......................................................................................................... 130 REFERENCES CITED .......................................................................................................... 131 v LIST OF TABLES Table Page 1-1. Summary of soymilk yield, solid yield and protein recovery as affected by three grinding methods .............................................................................................................. 24 1-2. Hydration ratioa in soaking .............................................................................................. 27 1-3. Percentage distribution of solid as affected by different grinding methods ..................... 28 1-4. Summary of four extraction methods ............................................................................... 29 1-5. Summary of soymilk yield, solid yield and protein recovery of four extraction methods ........................................................................................................................................... 30 1-6. Percentage distribution of solids as affected by different extraction methods ................. 32 2-1. Effect of variety, grinding and heating on trypsin inhititor (mg trpsin inhibited /g of dry soymilk) ............................................................................................................................ 41 2-2. Effect of variety, grinding and heating on Bowman-Birk trypsin inhibitor (mg chymotrypsin inhibited /g of dry soymilk) ....................................................................... 42 2-3. Estimated contents of individual inhibitors (µmol/g) ....................................................... 44 3-1. Effect of grinding methods, cooking methods and variety on total phenolic content (TPC) (mg of GAE/g of dry material) ............................................................................. 62 3-2. Effect of grinding methods, cooking methods and variety on total flavonoid content (TFC) (mg of CAE/g of dry material) .............................................................................. 67 3-3. Effect of grinding methods, cooking methods and variety on condensed tannin content (CTC) (mg of CAE/g of dry material) .............................................................................. 68 3-4. Effect of grinding methods, cooking methods and variety on DPPH scavenging activity (μmol of trolox/g of dry material) ..................................................................................... 72 3-5. Effect of grinding methods, cooking methods and variety on oxygen radical absorption capacity (ORAC) (μmol of trolox/g of dry material) ........................................................ 74 4-1. Effect of grinding methods, heating methods, and variety on selected odor compounds in soymilk (ppm). .............................................................................................................. 82 4-2. Effect of extraction methods, traditional stove cooking, and variety on selected odor compounds in soymilk (ppm) ........................................................................................... 95 5-1. Classification of 12 isoflavones ...................................................................................... 104 5-2. Effect of grinding, heating methods and variety on isoflavone content and profile in Prosoy soymilk (μg or nmol/g of dry material) .............................................................. 109 vi 5-3. Effect of grinding, heating methods and variety on isoflavone content and profile in black soybean soymilk (μg or nmol/g of dry material) ................................................... 112 5-4. Distribution of isoflavones in different fractions of Prosoy soymilk (μg or nmol/g of dry material) .................................................................................................................... 115 5-5. Distribution of isoflavones in different fractions of black soymilk (μg or nmol/g of dry material) .................................................................................................................... 117 5-6. Effects of extraction methods and cooking on isoflavone content and profile of Prosoy soymilk (ug or nmol/g of dry material) ........................................................................... 126 vii LIST OF FIGURES Figure Page 1-1. Flow diagram of extraction Method #1 (control) ............................................................. 18 1-2. Flow diagram of extraction Method #2 (extraction with okara-washing water of last batch) ................................................................................................................................. 19 1-3. Flow diagram of extraction Method #3 (extraction with