Final Examination for the Degree of MSc - April X. Xu

Examining Committee
Dr. Donald Mercer, Chair
Dr. Michael Rogers, Advisor
Dr. Maria Corradini, Advisory Committee Member
Dr. Loong-Tak Lim, Department Member

TITLE: SOUS VIDE COOKING CHANGES LIPID BIOACCESSIBILITY OF EGG YOLKS

ABSTRACT: Significant correlations exist between structure and lipid bioaccessibility in egg yolks. Structural changes of raw (20°C) and cooked egg yolks (65 – 85°C) were determined using rheology, thermal analysis, Fourier-transform infrared spectroscopy. A multicompartmental in vitro gastrointestinal digestion system, TIM-1, was used to elucidate the effects of cooking temperature on three bioaccessibility parameters – total bioaccessibility, induction time, and rate of lipolysis. Results showed significant differences in bioaccessibility parameters between treatments in cumulative bioaccessibility, such that it decreased from 25.08 – 29.43% in raw yolks to 19.77 –24.08% in 85°C yolks. Induction time also increased from 138.4 – 156.5 minutes in raw yolks to 158.3 – 184.2 minutes in 85°C yolks. Visualization and image analysis of raw and cooked yolk during digestion showed obvious differences in particle size. Lipid bioaccessibility had a negative relationship between storage modulus (G′) and intermolecular β-sheets content, whereas increases in peak enthalpy was positively related to increases in lipid bioaccessibility.