Sous vide cooking changes lipid bioaccessibility of egg yolks
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 multi-compartmental 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 25.1 – 29.4% in raw yolks to 19.8 –24.1% in 85°C yolks. Induction time also increased from 138 – 156 min in raw yolks to 158 – 184 min 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 were positively related to increases in lipid bioaccessibility.