Utilization of a By-Product from Goji Berry Beverage as a Value-Added Ingredient in Chinese Steamed Bread by Yi Yang A Thesis Presented to The University of Guelph In partial fulfilment of requirements for the degree of Master of Science in Food Science program Guelph, Ontario, Canada ©Yi Yang, September, 2016 ABSTRACT UTILIZATION OF A BY-PRODUCT FROM GOJI BERRY BEVERAGE AS A VALUE-ADDED INGREDIENT IN CHINESE STEAMED BREAD Yi Yang Advisor: Dr. Massimo F. Marcone University of Guelph, 2016 Co-advisor: Dr. Sunan Wang Committee member: Dr. Sanaa Ragaee Chinese steamed bread (CSB) is an Asian staple food made by steaming fermented wheat dough. Goji berry (Lycium barbarum) is considered an excellent source of several bioactive components which have been associated with several health benefits. During processing of beverages from goji berries, a significant amount of solid material is produced as a waste. This study was designed to evaluate the nutritional quality of goji berry by-product (GBP) and the feasibility of fortifying CSB with the GBP. Incorporating the GBP in the formula had significant adverse effect on the rheological properties of wheat flour to different extents. On the other hand, increasing the GBP concentration in the formula increased the free phenolics and consequently the antioxidant capacities of the CSB. Sensory evaluation of the composite breads indicated acceptability comparable to that of the control wheat bread. These findings suggest the possibility of utilizing GBP as a value added ingredient to produce functional CSB. ACKNOWLEDGEMENTS I would like to express my sincere thanks to my advisor Prof. Massimo Marcone for his guidance, input and inspiration throughout my study. He always guided me clearly and helped to make the research fun for me. I wish to express my profound gratitude to Dr. Sanaa Ragaee. She unselfishly let me join in her project. With her expertise and enthusiasm, she made significant efforts to guide my research project step by step. During my thesis-writing period, she gave all her time to help me polish the thesis for several times in a timely fashion. With her encouragement, I felt so motivated and grateful to achieve my goals. I also would like to express my sincere gratitude to my co-advisor, Dr. Sunan Wang. I have been fortunate to conduct my MSc study with these three excellent professors. They were always there and made me get through all the challenges. I would also like to thank Dr. Xin Hu at Guelph Food Technology Centre for his technical assistance. Also, I want to thank my friends who helped me out in completing the project. Moreover, I wish to thank my family for their personal support and devotion to help me to reach my goals. iii TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii ACKNOWLEDGEMENTS ............................................................................................... iii TABLE OF CONTENTS ................................................................................................... iv LIST OF TABLES ........................................................................................................... viii LIST OF FIGURES ........................................................................................................... ix CHAPTER 1: INTRODUCTION ....................................................................................... 1 CHAPTER 2: LITERATURE REVIEW ............................................................................ 5 2.1. Chinese steamed bread ............................................................................................. 5 2.2. CSB quality .............................................................................................................. 7 2.3. Rheological properties of dough and their roles in CSB quality ............................. 8 2.3.1. Type of wheat flour used in CSB ...................................................................... 8 2.3.2. Protein ............................................................................................................... 9 2.3.3. Starch .............................................................................................................. 11 2.4. Additional ingredients of CSB ............................................................................... 12 2.4.1. Sourdough starter ............................................................................................ 13 2.4.2. Dietary fiber and resistant starch .................................................................... 14 2.4.3. Phenolic .......................................................................................................... 15 2.5. Goji berry ............................................................................................................... 17 2.5.1. Phytochemical profile of goji berry ................................................................ 17 2.5.2. Antioxidant activity of goji berry ................................................................... 18 iv 2.5.3. Applications of goji berry ............................................................................... 18 2.5.4. Applications of by-products from beverage production ................................. 20 CHAPTER 3: IMPACT OF THE GOJI BY-PRODUCT ON THE RHEOLOGICAL PROPERTIES OF WHEAT FLOUR ............................................................................... 21 3.1. Abstract .................................................................................................................. 21 3.2. Introduction ............................................................................................................ 22 3.3. Materials ................................................................................................................ 23 3.4. Methods .................................................................................................................. 23 3.4.1. Preparation of goji berry by-product powder and composite wheat flours .... 23 3.4.2. Proximate analysis .......................................................................................... 24 3.4.3. Color measurement of soft wheat and composite flours ................................. 24 3.4.4. Rheological properties of soft wheat and composite flours ............................ 25 3.4.5. Pasting properties of soft wheat and composite flours ................................... 25 3.4.6. Statistical analysis ........................................................................................... 26 3.5. Results and discussion ........................................................................................... 26 3.5.1. Chemical composition .................................................................................... 26 3.5.2. Color of soft wheat and composite flours ....................................................... 27 3.5.3. Rheology of soft wheat and composite flours ................................................ 28 3.5.4. Pasting properties of soft wheat and composite flours ................................... 30 3.6. Conclusion ............................................................................................................. 32 CHAPTER 4: EFFECT OF GOJI BERRY BY-PRODUCT ON QUALITY OF CHINESE STEAMED BREAD ......................................................................................................... 33 v 4.1. Abstract .................................................................................................................. 33 4.2. Introduction ............................................................................................................ 34 4.3. Materials ................................................................................................................ 35 4.4. Methods .................................................................................................................. 35 4.4.1. Preparation of CSB ......................................................................................... 35 4.4.2. Specific volume of CSB ................................................................................. 38 4.4.3. Firmness of CSB ............................................................................................. 38 4.4.4. Color measurement of CSB ............................................................................ 38 4.4.5. Microbiological shelf-life of CSB .................................................................. 50 4.4.6. Sensory evaluation .......................................................................................... 50 4.4.7. Free phenolic content (FPC) ........................................................................... 40 4.4.8. Ferric-reducing antioxidant power (FRAP) assay .......................................... 40 4.4.9. Radical scavenging activity (DPPH) assay ..................................................... 41 4.4.10. Statistical analysis ......................................................................................... 41 4.5. Results and discussion ........................................................................................... 42 4.5.1. Specific volume of CSB ................................................................................. 42 4.5.2. Firmness of CSB ............................................................................................. 43 4.5.3. CSB Color ......................................................................................................