Final Examination for the Degree of PhD - Bonnie Kung

Date and Time

Location

Food Science lecture room 128

Details

DEFENCE ANNOUNCEMENT Final Examination for the Degree of PhD - BONNIE KUNG

Examining Committee

Dr. Loong-Tak Lim, Chair 
Dr. Amanda Wright, Co-Advisor 
Dr. Lisa Duizer, Advisory Committee Member  
Dr. Alison Duncan, Department Member
Dr. Zeynep Ustunol, External Examiner 

TITLE: EFFECT OF CO-CONSUMPTION OF ENHANCED PROTEIN CONCENTRATION AND  MODIFIED CASEIN:WHEY RATIO MILK WITH CEREAL ON SATIETY, FOOD INTAKE AND  GLYCEMIC RESPONSE AND THE ELUCIDATION OF MECHANISMS THROUGH IN VITRO DIGESTION 
 

ABSTRACT: 

Exploring casein and whey proteins as a dietary intervention for managing Type 2 diabetes is of interest because of their capacity to modulate postprandial blood glucose (BG) and satiety. Yet, whether these proteins varying in concentrations and ratios co-ingested with high-carbohydrate cereal results in different effects, is unknown. The overall objective was to determine the effect of a novel formulation on glycemic and appetite response and to investigate the possible mechanism associated with gastric emptying (by indirect paracetamol concentration) via increased plasma branched-chain amino acids (BCAAs). A randomized, double-blinded, crossover human study was conducted to investigate effects on BG, appetite and subsequent caloric intake healthy adults (n=32) following co-consumption by of breakfast cereal and milk, with either 80:20 (normal) or 40:60 (modified) casein-to-whey protein ratios at normal (3.1wt%) or high protein (9.3wt%) concentration or control (water with permeate). Plasma AAs and paracetamol were further studied from subset participants (n=12). In vitro digestion experiments were conducted on the hydrolysis of the breakfasts, gastrointestinal viscosity and bio-accessibilities of sugars and AAs, and comparisons with in vivo responses. Pre-lunch(0-120min) BG concentrations were lowered after milk consumption compared to control. High protein milks (9.3wt%) lowered BG and paracetamol and plasma AAs increased, compared to 3.1wt% treatments. Also, 40:60 milks increased BCAA, compared to 80:20, but there was a modest effect of ratio on BG and paracetamol. Subsequent food intake was modestly affected by treatments in the females, but not in the overall. Post-lunch(120–200min) appetite was reduced by 9.3wt% compared to 3.1wt% protein concentration, as plasma AAs remained elevated. Higher in vitro gastrointestinal viscosity was observed for the 9.3wt%80:20 treatment. After simulated duodenal digestion, milk treatments had lower reducing sugars. Some in vitro-in vivo trends were observed between gastric viscosity and attenuated paracetamol, reducing sugar and BG, and release of free AAs. However, there was no trend between viscosity and sugar release. These results support that the observed postprandial attenuation of BG and post-lunch appetite were related to higher protein concentration of the dairy beverage, with some impact of higher whey proportion, through the possible mechanism of slowing gastric emptying and some amylolysis reduction. 

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