Regulatory effects of betaine on the heat-induced aggregation and emulsifying properties of egg yolk plasma.

This paper focused on egg yolk plasma (EYP) and systematically analyzed the critical factors underlying heat-induced EYP instability. 76 °C is the key temperature for phase behavior transformation of EYP, and 72 °C marks the rheological transition point of thermal aggregation rate. Heat induction caused particle size of EYP increase by 6.20 times and emulsifying activity decrease by 6.90%, corresponding to larger and more aggregated emulsion droplets. Protein structure became more compact, with β-sheet content increasing by 32.48% and reduced fluorescence intensity. SDS-PAGE revealed that β-livetin, γ-livetin and apo-LDL were the key proteins involved in heat-induced EYP aggregation. Betaine altered hydrogen bond and water binding to suppress particle growth of EYP proteins, yet lost its protective effect on key proteins at 76 °C. The results clarify the thermal aggregation rules of EYP and liquid egg yolk, and lay a theoretical foundation for the production of thermally stable liquid egg products.