Structural characterization, functional properties and formation mechanism of alkali-thermal induced egg white gel:...

The traditional single-alkali method for protein gelation suffers from slow processing and empirical control. Heat alone cannot produce firm, transparent gels. Understanding the synergy between alkali and heat is therefore important for both gelation theory and practical processing. In this study, alkali-thermal induced egg white gelation (EWG) was investigated using multi-scale techniques including texture analysis, rheology, low-field nuclear magnetic resonance (LF-NMR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS). Increasing processing intensity first improved gel properties but then caused a decline. Under optimal conditions (pH 11.5, 75 °C, 40 min), the gel formed a dense network stabilized mainly by disulfide and ionic bonds. A three-stage gelation mechanism is proposed. The first stage is ionic bond-dominated aggregation. The second stage involves disulfide bond-driven network strengthening. The third stage is a reorganization process where excessive processing leads to structural deterioration. This work advances the understanding of alkali-thermal protein gelation by revealing the interplay between intermolecular forces and hierarchical structures, and provides a theoretical framework and practical guidance for protein gelation under coupled chemical and thermal stimuli.