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Characterization of Cereal Arabinoxylans and Their Health Benefits

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Characterization of Cereal Arabinoxylans and Their Health Benefits Characterization of Cereal Arabinoxylans and their Health Benefits By Lovemore Nkhata Malunga A Thesis submitted to the Faculty of Graduate Studies of The University of Manitoba In Partial fulfillment of the Requirements for the degree of DOCTOR OF PHILOSOPHY Department of Food Science University of Manitoba Winnipeg, Manitoba Copyright © 2016 by Lovemore Nkhata Malunga ii Acknowledgement Many thanks should go to my advisor Dr. Trust Beta for giving me the opportunity to pursue doctoral studies. I am very grateful for her never ending support, patience and guidance during my entire doctoral studies. I would like also to acknowledge support given by Dr. Peter Eck during glucose transport assays for which I am so grateful. Many thanks should also go to Dr. Marta Izydorczyk for guidance and technical support during isolation and characterization of arabinoxylans. A special thank you to my committee members Dr. James Friel and Dr. Peter Jones for their support and guidance during my research. I would like also to thank the Academic Enhancement Fund (AEF) and the Faculty of Graduate Studies for funding my studies through GETs program. This research was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) (Discovery Grant Program) and the Canada Foundation for Innovation (CFI-Leaders Opportunity Fund and CFI-New Opportunities Fund). Many thanks go to Cargill Limited for provision of wheat aleurone samples. I am also grateful to the financial support received from the American Association of Cereal Chemists International (AACCI) Foundation Graduate fellowship. Furthermore, I would to like to thank the staff and students of the Department of Food Science for creating an enabling environment to conduct my studies. Special thanks to departmental technicians (Pat Kenyon, Alison Ser, Yang Qiu, and Babak Sobhi) and all my friends in our laboratory (Victoria Ndolo, Kabu Masisi, Kuku Biney, and Lilei Yu). Many thanks to summer students (Carly Isaak, Kellen Da Cruz Rodrigues, Ce Zhou, and Huan) for their assistance in carrying out experiments. iii Finally many thanks to my family (Alexandra and Chikondi) for their support and encouragement. I am also grateful to God for everything – without you nothing is possible! iv Dedication To my parents (Esau and Margret) and my family (Alexandra and Chikondi) v Table of Contents Aknowledgement…………………………………………………………………………………ii Dedication………………………………………………………………………………………...iv Table of Contents…………………………………………………………………………………v List of Tables……………………………………………………………………………………xiii List of Figures…………………………………………………………………………………..xiv Abstract………………………………………………………………………………………….xix General Introduction, Hypothesis and Objectives .......................................................................... 1 Introduction ...................................................................................................................... 1 Research hypothesis ......................................................................................................... 4 Research objectives .......................................................................................................... 4 Literature Review .................................................................................................................... 6 Feruloylated Arabinoxylans of Cereal Grains .................................................................. 6 2.1.1 Occurrence and distribution of arabinoxylans in cereals .......................................... 6 2.1.2 Chemistry of cereal arabinoxylans............................................................................ 7 2.1.3 Method of extraction of arabinoxylans ..................................................................... 9 Phenolic Compounds in Cereal ...................................................................................... 10 2.2.1 Occurrence of phenolic acids in cereal grains ........................................................ 10 vi 2.2.2 Absorption and metabolism of cereal phenolic compounds ................................... 12 Glucose Absorption and Metabolism ............................................................................. 14 Whole Grain and Diabetes Management ....................................................................... 15 Arabinoxylans in Diabetes Prevention and Management .............................................. 16 2.6 Whole Grain and Gut Health ............................................................................................... 18 References ...................................................................................................................... 20 Antioxidant Capacity of Water-Extractable Arabinoxylan from Commercial Barley, Wheat, and Wheat Fractions ..................................................................................................................... 45 Abstract .......................................................................................................................... 45 Introduction .................................................................................................................... 46 Materials and methods ................................................................................................... 49 3.3.1 Sample and chemicals ............................................................................................. 49 3.3.2 Preparation of water extractable NSP ..................................................................... 49 3.3.3 Preparation of WEAX ............................................................................................. 51 3.3.4 Chemical composition of WEAX and NSP ............................................................ 51 3.3.5 Determination of antioxidant activity of WEAX and NSP ..................................... 54 3.3.6 Statistical analysis ................................................................................................... 56 Results and discussion .................................................................................................... 56 3.4.1 Yield and chemical composition ............................................................................. 56 3.4.2 Phenolic acid composition ...................................................................................... 58 vii 3.4.3 Total phenolic compounds ...................................................................................... 60 3.4.4 Antioxidant capacity ............................................................................................... 60 Conclusions .................................................................................................................... 65 Acknowledgments .......................................................................................................... 65 References ...................................................................................................................... 65 Effect of Water Extractable Arabinoxylan from Wheat Aleurone and Bran on Lipid Peroxidation and Factors Influencing their Antioxidant Capacity ............................................... 80 Abstract .......................................................................................................................... 80 Introduction .................................................................................................................... 81 Materials and Methods ................................................................................................... 83 4.3.1 Sample and chemicals ............................................................................................. 83 4.3.2 Preparation of water extractable arabinoxylan from wheat bran and aleurone ...... 83 4.3.3 Characterisation of the water extractable arabinoxylan extracts ............................ 84 4.3.4 Prevention of lipid hydroperoxides formation in simulated gastric digestion ........ 85 4.3.5 Determination of antioxidant activity using DPPH, ORAC, and ABTS assays ..... 86 4.3.6 Statistical analysis ................................................................................................... 86 Results and Discussion ................................................................................................... 86 4.4.1 Composition of water extractable preparations from wheat bran and wheat aleurone 86 4.4.2 Molecular weight determination ............................................................................. 88 viii 4.4.3 1H NMR analysis .................................................................................................... 88 4.4.4 Prevention of lipid hydroperoxides formation ........................................................ 89 4.4.5 Antioxidant capacity of water extractable arabinoxylans ....................................... 90 Conclusion ...................................................................................................................... 93 Acknowledgement .......................................................................................................... 93 References ...................................................................................................................... 93 Antioxidant capacity of arabinoxylan oligosaccharide fractions prepared from wheat aleurone using Trichoderma viride or Neocallimastix patriciarum xylanase ............................................ 113 Abstract .......................................................................................................................
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