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ABSTRACT DUNN, MARSHALL ROBERT. Viscosity and Gel

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ABSTRACT DUNN, MARSHALL ROBERT. Viscosity and Gel ABSTRACT DUNN, MARSHALL ROBERT. Viscosity and Gel Formation of Micellar Casein Concentrates. (Under the direction of Dr. MaryAnne Drake). Milk protein products have gained widespread use in the food and sports nutrition industries. Processing techniques, such as micro and ultrafiltration (UF), have led to the development of novel protein ingredients, particularly micellar casein concentrate (MCC). Liquid MCC has unique rheological properties, specifically that it will form a thermo-reversible gel at colder temperatures. The mechanisms responsible for the rheological properties of MCC are not completely understood but are thought to be related to jamming of the micelles and to the dissociation of β-casein from the micelle at colder temperatures. This thesis determined the basis for viscosity increase and cold gelation of liquid MCC at protein concentrations from 6 to 20% during refrigerated storage. Skim milk (ca 350 kg) was pasteurized (72°C for 16 sec) and filtered through a ceramic MF system to make micellar casein concentrate (MCC). The liquid MCC was immediately concentrated via a plate ultrafiltration (UF) system to 18% protein (w/w). The MCC was then diluted to various concentrations (6 to 18%, w/w). Apparent viscosity readings were collected from liquid MCC samples (6, 8, 10, 12% protein w/w) at 4, 20, and 37°C. Instron compression force of MCC gels (14, 16, 18% protein w/w) was collected over a period of 2 weeks at 4°C. The maximum compressive load was compared at each time point to assess the changes in gel strength over time. Supernatants from MCC of 6.5 and 10.5% protein were collected after ultracentrifugation (100,605 x g for 2 h at 4, 20 and 37°C) and the nitrogen distribution (total, noncasein, casein, and nonprotein nitrogen) was determined. The entire experiment was replicated 3 times. The highest protein concentrations of MCC formed gels almost immediately on cooling to 4°C, while lower concentrations of MCC were viscous liquids. The protein, casein, and casein as a percent of true protein in the liquid phase around casein micelles in MCC increased with increasing casein concentration of the MCC and with decreasing temperature. Casein as a percent of true protein at 4°C in the liquid phase around casein micelles increased from about 16% for skim milk to about 78% for an MCC containing 10.5% protein. AV of MCC solutions in the range of 6 to 13% casein increased with increasing casein concentration and decreasing temperature. There was a strong temperature by protein concentration interaction for viscosity with AV increasing non-linearly with decreasing temperature at high protein concentration. MCC containing 16 and 18% casein gelled upon cooling to form a gel that was likely a particle jamming gel. These gels increased in strength over 10 days of storage at 4oC, likely due to migration of casein out of the micelles and interaction of the non-micellar casein to form a network that further strengthened the random loose particle jamming gel structure. With an increased understanding of the mechanism of cold thickening of MCC, there may be potential to replace hydrocolloids for thickening and stabilizing beverages with a clean label ingredient and also to provide a high level of protein with superior flavor and color. Viscosity and Gel Formation of Micellar Casein Concentrates by Marshall Robert Dunn A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Master of Science Food Science Raleigh, North Carolina 2021 APPROVED BY: _____________________________ _____________________________ Dr. MaryAnne Drake Dr. Clint Stevenson Chair of Advisory Committee _____________________________ Dr. Dana Hanson BIOGRAPHY Marshall Robert Dunn was born on June 11, 1990 to his amazing parents, Holly and Michael Dunn. Marshall spent most of his adolescence in Ithaca, NY and Salem, UT. Growing up, Marshall was exposed to food science through his father who worked as a food scientist and then taught the subject at Brigham Young University. In 2008 Marshall attended Brigham Young University and followed in his father’s footsteps, receiving his Bachelor of Science in Food Science, with a minor in Chemistry. Upon finishing his undergraduate, Marshall worked for a small, local, startup business for a year before accepting a job doing beverage R&D with Bolthouse Farms in Bakersfield, CA. It was while working at Bolthouse that Marshall met his future wife, Lauren Gillespie, who helped to move his love of food science beyond the lab and into the kitchen. To further his education Marshall left Bolthouse and began his graduate studies at North Carolina State University with Dr. MaryAnne Drake in 2018. Towards the end of Marshall’s master’s program, the world was hit with the COVID-19 pandemic, adding uncertainty to the future. It was during this time that Marshall and Lauren got engaged, married, and pregnant with their first child, all while finishing his thesis. Marshall hopes to be able to use his past experience and the knowledge gained during his master’s degree to positively impact the future direction of the dairy industry and to share his love of food and his passion of science with the rising generation. ii DEDICATION I would like to thank Dr. MaryAnne Drake and Dr. Dave Barbano for their immense help, direction, and support during my time as a master’s student, especially after the restrictions and changes from COVID-19. Your understanding, patience and help during these unprecedented times have been invaluable. I am eternally grateful for all the time you both spent helping me with my writing, interpreting data and helping me complete this thesis. I also want to thank Dr. Hanson and Dr. Stevenson for being on my committee and helping me through this process. I want to express my sincere gratitude to all my lab and classmates who helped me out along the way, I could not have done this without all of your help. I would especially like to thank the pilot plant crew- Brandon for being our fearless leader and a mentor, Daniel for being our resident ceramic MF operator, Alex for being a jack of all trades, and Hayden for being side by side with me every step of the way. I will forever feel bonded to you all. My family was instrumental in helping me get through this master’s program; thank you for all your prayers and support. There were multiple times where I felt God’s guidance and I attribute it directly to all your prayers and faith on my behalf. Dad, I wanted to especially thank you for all your advice and help, it truly helped me to keep moving forward. Most importantly I want to thank my amazing wife Lauren. The idea of finishing my degree and immediately marrying you was the dream that kept me sane throughout all the craziness. Without that light at the end of the tunnel I do not think that I would have been able to make it. And lastly, to my soon to be baby girl Kendall, ultimately this degree is so that you can have the best life I can give you. I love you and your mom more than I could ever express. This thesis is dedicated to you both. iii TABLE OF CONTENTS LIST OF TABLES ......................................................................................................................... vi LIST OF FIGURES ...................................................................................................................... vii CHAPTER 1: LITERATURE REVIEW: THE PRODUCTION, PHYSICAL PROPERTIES, AND RHEOLOGICAL TESTING METHODS OF MICELLAR CASEIN CONCENTRATE ....1 Abstract ........................................................................................................................................2 Introduction ..................................................................................................................................3 Milk Fundamentals ......................................................................................................................4 Structure of Casein Micelle Models ............................................................................................5 Hydrophobic Properties of β-casein.............................................................................................8 MCC Production ........................................................................................................................10 Liquid vs Spray Dried MCC ......................................................................................................15 Uses and Functionality of MCC ................................................................................................19 Functional Properties of MCC ...................................................................................................25 Protein Concentration and Steric Effects ...................................................................................26 Types of Fluids ..........................................................................................................................27 Gels ............................................................................................................................................29 Jammed Systems ........................................................................................................................30 Cold Gelation of MCC ...............................................................................................................32 Cold Gelation of HC-MCC ........................................................................................................33
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