Egg white protein under thermal stress: Thermal aggregation orientation and gel properties decline

This study investigates the effects of varying heat stress temperatures (56 °C to 76 °C) on the gel characteristics of egg white protein. The results indicate that when the heat stress temperature exceeds 60 °C, the textural properties, water-holding capacity, and freeze-thaw stability of egg white gel (EWG) decrease to varying extents compared to untreated EWG. At 76 °C, the proportion of free water in EWG increases from 0.9 % to 1.4 %, while rigidity, as observed in rheological analysis, decreases by approximately 48.6 %. Additionally, the α-helix content in the secondary structure reduces by approximately 20.1 %, and notable changes occur in the crystalline structure, with decreased peak intensities in Ultraviolet and both intrinsic and extrinsic fluorescence spectra. Furthermore, weakened intermolecular interactions in EWG result in the formation of larger aggregates within the microstructure. These findings suggest that increased heat stress promotes protein aggregation into disordered clusters, forming a porous gel network that releases water under external forces. This explains the observed decline in texture and water-holding capacity. The study provides a theoretical basis for improving the production and processing of egg white protein products and developing future strategies to mitigate protein aggregation.