IMPROVEMENT OF THE PHYSICOCHEMICAL ATTRIBUTES AND ANTIOXIDANT PROFILES FROM PULSE SEEDS THROUGH GERMINATION A Dissertation Submitted to the Graduate Faculty of the North Dakota State University of Agriculture and Applied Science By Minwei Xu In Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Program: Cereal Science November 2019 Fargo, North Dakota North Dakota State University Graduate School Title IMPROVEMENT OF THE PHYSICOCHEMICAL ATTRIBUTES AND ANTIOXIDANT PROFILES FROM PULSE SEEDS THROUGH GERMINATION By Minwei Xu The Supervisory Committee certifies that this disquisition complies with North Dakota State University’s regulations and meets the accepted standards for the degree of DOCTOR OF PHILOSOPHY SUPERVISORY COMMITTEE: Dr. Bingcan Chen Chair Dr. Clifford Hall Dr. Paul Schwarz Dr. Julie Garden-Robinson Approved: 11/14/2019 Dr. Richard Horsley Date Department Chair/Program Coordinator ABSTRACT Edible pulse seeds are good sources of food ingredients. Germination has been regarded as an effective process to further improve nutrient digestibility and accessibility of pulse seeds. Our aim was to observe the effect of germination on proximate composition, physicochemical attributes, and phenolic profiles of chickpea (Cicer arietinum L.), lentil (Lens culinaris Merr.), and yellow pea (Pisum sativum L.). In addition, mechanisms of how germination affects the antioxidant activity of phenolic compounds were proposed. Chemical composition, thermal, pasting, and moisture adsorption properties of pulse flours were investigated over 6 days of germination. Protein contents increased by 3 percent points for all pulses over germination. However, lentil had the highest protein content. Lipid contents decreased over germination with chickpea having the greatest decline, from 8.00 to 5.90 g/100g (d.b.). Total starch decreased in lentil and yellow pea during germination. Thermal properties of pulse flours changed slightly, while pasting properties varied among pulses. The highest final viscosities for chickpea, lentil, and yellow pea flours were 1061, 981, and 1052 cP and were observed after 2, 1, and 0 days of germination, respectively. Moisture adsorption isotherms showed improved water adsorption capabilities after germination. Soluble free (SFPs) and polar soluble bound phenolic compounds (PSBPs) were extracted from germinated pulse seeds. Their antioxidant activities were evaluated using both the in vitro system and stripped soybean oil (SSO)-in-water emulsions. Liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry and size- exclusion chromatography with multiangle-light-scattering and refractive-index detection were employed to analyze the phenolic composition and molar mass, respectively. Antioxidant activities of SFPs increased in both in vitro and SSO-in-water emulsion system, however, much iii lower than those of PSBPs based on SSO-in-water emulsion system. The effect of germination on PSBPs in SSO-in-water emulsion varied between pulses. By virtue of chemometric analysis, nine phenolic compounds were speculated as the pivotal phenolic compounds responsible for the antioxidant activity of PSBPs. In particular, the molar masses of PSBPs had a positive relationship with their antioxidant activity. Protective and co-antioxidative principles were proposed as reasons for the variability of antioxidant activities of PSBPs in oil-in-water emulsions with germination. iv ACKNOWLEDGMENTS I would like to acknowledge many people for their assistance and support. First, I am grateful to my advisor, Dr. Bingcan Chen, for the opportunity to pursue graduate studies and for unflagging patience throughout various guidance of my career. I have thoroughly enjoyed working independent yet supportive environment of his research group. If I have to grade for him, his score is 200%. I am also grateful to my other graduate committee members: Dr. Clifford Hall, Dr. Paul Schwarz, and Dr. Julie Garden-Robinson. Their patient guidance and desire for my success have been deeply appreciated. My thanks are also due to all who provided technical assistance: to Allen Peckrul, for kind assistance with many laboratory questions; to James Gillespie, for considerable involvement in the instrument maintenance and troubleshooting; and to Dr. Zhao Jin and Dr. Jiajia Rao, for invaluable experiment advice; to Dr. Jae Ohm, for kind instructing and allowing the use of many instruments; to Dr. Frank Manthey, Dr. Simsek Senay, and Dr. Anuradha Vegi, for teaching me useful knowledge in the area of cereal science. To my family and friends who have supported and loved me during the most stressful times, words will ever fail to express my gratitude. To Dr. Bingcan Chen and Dr. Jiajia Rao, thank you for the countless parties you invited me and your help in my daily life, such as fishing, skiing, and even taking care of my daughter. To my group members, Jing Wan, Yang Lan, Fengchao Zha, thank you to accompany me through the first semester, which is the hardest one. To my friend Serap Vatansever, thank you for organizing so many parties in the hardest time so that we can enjoy our campus lives. To my parents, Qiuliang Xu and Yue Jia, I cannot say how much your love and complete support in all I have done has meant. v DEDICATION I dedicate this work to my wife and daughter: To my wife, Zhao Jin, without your encourage and support. This work would never have been accomplished or even attempted. To my daughter, Kexin Xu, your happiness is the best award to me. Hope you can have a happy life with your own diligence in the future. vi TABLE OF CONTENTS ABSTRACT ................................................................................................................................... iii ACKNOWLEDGMENTS .............................................................................................................. v DEDICATION ............................................................................................................................... vi LIST OF TABLES ........................................................................................................................ xii LIST OF FIGURES ..................................................................................................................... xiii CHAPTER 1. GENERAL INTRODUCTION ............................................................................... 1 1.1. Introduction ............................................................................................................. 1 1.2. References ............................................................................................................... 4 CHAPTER 2. LITERATURE REVIEW ........................................................................................ 9 2.1. Pulse Classes Cultivated in North Dakota .............................................................. 9 2.2. Proximate Composition of Pulse seeds ................................................................... 9 2.2.1. Protein profiles of pulse seeds .................................................................... 9 2.2.2. Carbohydrate profiles of pulse seeds ........................................................ 10 2.2.3. Lipid profiles of pulse seeds ..................................................................... 12 2.3. The Functionality of Pulse Flours ......................................................................... 13 2.3.1. Water absorption capacity......................................................................... 13 2.3.2. Thermal properties .................................................................................... 15 2.3.3. Pasting properties ...................................................................................... 18 2.3.4. Phenolic compounds ................................................................................. 19 2.4. Germination of Pulse Seeds .................................................................................. 32 2.4.1. Effect of germination on proximate compositions.................................... 32 vii 2.4.2. Effect of germination on the quantity of phenolic compounds in pulse seeds .......................................................................................................... 39 2.4.3. Effect of pulse seeds germination on the antioxidant activity of phenolic compounds in preventing lipid oxidation ................................... 41 2.4.4. Germinated pulse seeds as food ingredients ............................................. 43 2.5. References ............................................................................................................. 44 CHAPTER 3. EFFECT OF GERMINATION ON THE CHEMICAL COMPOSITION, THERMAL, PASTING, AND MOISTURE SORPTION PROPERTIES OF FLOURS FROM CHICKPEA, LENTIL, AND YELLOW PEA ............................................................................. 63 3.1. Abstract ................................................................................................................. 63 3.2. Introduction ........................................................................................................... 64 3.3. Materials and Methods .......................................................................................... 66 3.3.1. Chemicals .................................................................................................. 66 3.3.2. Germination of pulse seeds ......................................................................