Phospholipids molecular species, proteins secondary structure, and emulsion microstructure of egg yolk with reduced polar and/or nonpolar lipids

This study investigated the phospholipids (PLs) molecular species (PLs-MS), protein secondary structure (PSS), and emulsion microstructure of the egg yolk (EY) treated with supercritical-CO2 (T1), hexane (T2), and ethanol {at room temperature (T3) and 65 degrees C (T4)}. PLs-MS, PSS, and microstructure of EY emulsion were investigated with UPLC-Q-TOF-MS, Fourier-transforms infrared and Raman spectroscopy, and confocal laser scanning mi-croscope, respectively. Predominant PLs molecular fractions were C18:0-C20:4, C18:0-C20:4, C16:0-C18:2, C16:0, C18:0-C18:2, and d18:1/16:0, for phosphatidylcholine, phosphatidylethanolamine, phosphatidylinosi-tol, lysophosphatidylcholine, sphingomyelin, and phosphatidylserine, respectively. All the PLs-MS were highest for T1 and many of them (C14:0-C16:0, C18:0-C18:1, C18:0-C20:3) were absent in T2, T3, and T4. PSS com-ponents (alpha-helices, beta-sheets, beta-turn, and random coil) were highest for T4, followed by T3, T2, T1, and control (non-treated EY). However, T1-added o/w emulsion showed excellent stability (95.64 %) with smaller and denser oil droplets due to better ionic interactions by synergistic effect of PLs-MS and PSS components.

Automated summary

This study examined the effects of supercritical-CO2, hexane, and ethanol treatments on the molecular species of phospholipids, protein secondary structure, and emulsion microstructure of egg yolk. The results showed that supercritical-CO2 treatment had the highest phospholipid molecular species, while hexane, ethanol at room temperature, and ethanol at 65 degrees C had fewer species. Protein secondary structure was the highest in ethanol at 65 degrees C and the lowest in the control group. However, the emulsion stability was significantly improved with the addition of supercritical-CO2-treated egg yolk.