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Evaluation of Pea Protein and Modified Pea Protein As Egg Replacers

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Evaluation of Pea Protein and Modified Pea Protein As Egg Replacers EVALUATION OF PEA PROTEIN AND MODIFIED PEA PROTEIN AS EGG REPLACERS A Dissertation Submitted to the Graduate Faculty of the North Dakota State University of Agriculture and Applied Science By Hieu Duy Hoang In Partial Fulfillment for the Degree of DOCTOR OF PHILOSOPHY Major Program: Cereal Science March 2012 Fargo, North Dakota North Dakota State University Graduate School Title EVALUATION OF PEA PROTEIN AND MODIFIED PEA PROTEIN AS EGG REPLACERS By HIEU HOANG 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: CLIFFORD HALL Chair FRANK MANTHEY CHARLENE WOLF-HALL SENAY SIMSEK Approved: 03/23/2012 DELAND MYERS Date Department Chair ABSTRACT Native yellow pea (Pisum sativum) protein isolates (PPIs) showed good foaming and emulsifying properties but a poor gelling characteristic. However, this can be corrected by Transglutaminase (TGase) treatment. PPIs were obtained using alkaline extraction method in which extracting pH, precipitating pH, flour–to–water ratio, and extraction time were optimized to obtain maximum yields and least change in protein functionalities. Extraction pH of 10.0, precipitating pH of 4.3, flour–to–water ratio of 1:6, and 30 minute extraction time were found to be optimum values for pea protein extraction. SDS–PAGE gels showed that the PPI had a very similar protein molecular weight profile as its original flour. TGase treatment was applied on PPIs at different pH levels from 4.3 to 7.0. The SDS–PAGE and RVA tests showed that treatment at pH 6.0 provided the best overall functionality. Large molecular weight (MW) proteins (~ 90,000 Da) and medium MW proteins (~50,000 – 80,000 Da) were the main substrates for TGase catalyzed reaction whereas most low MW the proteins (< 45,000 Da) were not involved. RVA results indicated that treatments at pH 6.0 and 7.0 had the highest viscosities but the treatment at pH 6.0 had better stability and consistency. Functionality tests indicated that modified PPIs possessed a better viscosity profile than the native PPIs but no improvement in gelling capacity and only minor impact on foaming and emulsifying properties. PPIs performance greatly depended on their final pHs. The foaming capacity, foaming stability, and emulsion capacity were significantly improved when the final pH of PPIs was adjusted from 4.3 to 7.0. The overall sensory evaluation results suggested that TGase–treated PPIs and PPIs were not yet able to replace egg in the cake system. Only PPI can replace egg in the cookie system. TGase–treated samples had iii a lower acceptability due to an “off–taste” and a “strange” flavor. Future work, therefore, should study TGase combined with other treatments to further improve PPIs functionalities. Purification should be integrated into extraction process and other food systems should also be included to extent the scope and role of modified PPIs in food industry. iv ACKNOWLEDGEMENTS I would like to express my appreciation to my major advisor, Dr. Clifford Hall, and committee, Dr. Charlene Woft–Hall, Dr. Senay Simsek, and Dr. Frank Manthey, for their continuous support, guidance and advices throughout my study and in the preparation of this thesis. Also I would like to thank Dr. Sam Chang and Dr. Khalil Khan for their great advices and guidance. I would also express my thanks to Mary Niehaus, Gloria Nygard, Mary Valenzuela and Dr. Zhisheng Liu for their technical help and permission for using their lab equipments. To my friends, thank you so much for being with me, listening and supporting me. Your support helps me a lot in the completion of this dissertation. Finally, I would like to express my love and my sincere thanks to my family, including my dad Hung Hoang, my mom Vien Ngo, my wife Trang Vu, and my little son Gia Minh, for their continuous support, encouragement and understanding. I love you all. v TABLE OF CONTENTS ABSTRACT ................................................................................................................. iii ACKNOWLEDGEMENTS ........................................................................................... v LIST OF TABLES ........................................................................................................ x LIST OF FIGURES ..................................................................................................... xii GENERAL INTRODUCTION ...................................................................................... 1 HYPOTHESIS .............................................................................................................. 5 OBJECTIVES ............................................................................................................... 6 LITERATURE REVIEW .............................................................................................. 7 1. PEA ............................................................................................................. 7 1.1. General information ............................................................................... 7 1.2. Pea protein ............................................................................................ 9 2. EGG PROTEIN.......................................................................................... 13 3. PROTEIN EXTRACTION METHODS ..................................................... 17 4. TRANSGLUTAMINASE MODIFICATION OF PROTEIN ...................... 22 5. CAKE AND COOKIE SYSTEMS ............................................................. 29 6. SENSORY AS AN ANALYTICAL METHOD.......................................... 32 PRELIMINARY INVESTIGATION ........................................................................... 34 1. STUDY ON DIFFERENT RAW MATERIALS ......................................... 34 2. PRELIMINARY CAKE SENSORY EVALUATION ................................ 34 MATERIALS AND METHODS ................................................................................. 37 vi 1. MATERIALS ............................................................................................. 37 1.1. Raw material ....................................................................................... 37 1.2. Transglutaminase................................................................................. 38 1.3. Chemical and other minor materials..................................................... 39 2. METHODS ................................................................................................ 39 2.1. Extracting methods .............................................................................. 39 2.2. Analytical methods .............................................................................. 46 2.2.1. Size distribution .............................................................. 46 2.2.2. Moisture content ............................................................. 47 2.2.3. Total starch ..................................................................... 47 2.2.4. Total ash determination ................................................... 49 2.2.5. Crude protein – combustion method ................................ 50 2.2.6. Electrophoresis ............................................................... 50 2.2.7. Foaming capacity and stability ........................................ 51 2.2.8. Emulsion capacity and stability ....................................... 52 2.2.9. Gelling capacity .............................................................. 53 2.2.10. Rapid viscosity analysis (RVA) ...................................... 54 2.2.11. Cake baking method ....................................................... 54 2.2.12. Cake measurement .......................................................... 56 2.2.13. Texture analysis .............................................................. 56 2.2.14. Cookie formula and bake quality ..................................... 57 2.3. Sensory evaluation............................................................................... 58 2.4. Experimental design and statistical evaluation of the data .................... 61 vii RESULTS AND DISCUSSION ................................................................................. 62 1. EXTRACTION PROCESS OPTIMIZATION ............................................ 62 1.1. Yellow pea flour characterization ........................................................ 62 1.2. Extraction pH ...................................................................................... 65 1.3. Precipitating pH (pI) ............................................................................ 69 1.4. Flour–to–water ratio ............................................................................ 71 1.5. Extraction time .................................................................................... 74 2. TRANSGLUTAMINASE MODIFICATION OF PEA PROTEIN .............. 81 2.1. Soluble starch degradation ................................................................... 82 2.2. Polymerized protein formation ............................................................ 82 2.3. Viscosity behaviors ............................................................................. 87 2.4. TGase–treated pea protein functionalities ............................................ 90 3. PEA PROTEIN EXTRACT CHARACTERIZATION ................................ 92 3.1. Protein content ...................................................................................
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