Effects of ethanol treatment on physicochemical and gel properties of egg yolk, plasma and granules

This study investigated ethanol-induced gelation mechanisms of egg yolk and its fractions (plasma and granules). The hardness of all samples increased with ethanol treatment time, with granules exhibiting significantly higher hardness than yolk and plasma. Free sulfhydryl content in yolk and plasma initially increased then decreased, whereas continuously declining in granules. Microstructural analysis revealed that ethanol disrupted plasma and granule structures, releasing their components that subsequently aggregated. The yolk formed compact gel network primarily stabilized by hydrogen bonds and hydrophobic interactions from plasma proteins, while granules contributed to higher hardness predominantly via disulfide bonds. FTIR spectra revealed β -sheet formation in yolk/plasma and increased random coils in granules. In conclusion, the synergistic gelation mechanism of yolk that plasma provided matrix formation via hydrophobic aggregation, while granules enhanced hardness through disulfide cross-linking. This study elucidated the distinct roles of yolk fractions in ethanol-induced gelation, providing insights for optimized ethanol-processed egg products.