Influence of initial protein structures and xanthan gum on the oxidative stability of O/W emulsions stabilized by whey protein.

In this article, oil-in-water (O/W) emulsions stabilized by natural whey protein concentrate (WPC) and microparticulated whey protein (MWP) and their mixtures with xanthan gum (XG) were prepared to investigate the lipid oxidative stability of O/W emulsions with the same interfacial composition but different interfacial structures. High-performance size exclusion chromatography, Fourier transform infrared spectrometry, X-ray diffraction analysis and steady-state fluorescence spectroscopy were used to reveal the differences in the structures of natural whey protein and the microparticulated whey proteins (MWP, pH 3.5-8.5). Dispersions of the proteins (70% w/w) and XG (30% w/w) were mixed to prepare the mixtures (protein-XG). Emulsions of 60% peanut oil that were stabilized by the proteins and the protein-XG mixtures were subjected to oxidation. In addition, the peroxide values (PVs) were measured to evaluate the oxidative stability of each emulsion. The MWP(pH 4.5)-XG and MWP(pH 6.5)-XG-stabilized emulsions showed high oxidative stabilities that were not significantly different from each other. The results indicated that a single complex layer formed by the spherical protein microparticles and XG can better inhibit the lipid oxidation of O/W emulsions than a double layer. This study has significant implications for the development of novel structures containing lipid phases that are susceptible to oxidation.