From thermodenatured intermediate state aggregates to gel network formation: Thermodynamic and kinetic analysis of the reaction process of soybean protein fraction

This study focused on protein fluorescence structure, particle size distribution, rheological changes, and the free energy of gelation reactions to investigate the thermal aggregation of β-conglycinin (7S) and globulin (11S) soybean proteins, as well as their thermodynamic and kinetic behavior during gelation induced by glucono-δ-lactone (GDL). The results indicate that the thermal denaturation of soybean protein 11S differs from that of 7S, exhibiting a variety of intermediate states and leading to the formation of multiple aggregates. When 7S and 11S coexist, their interactions lead to the formation of 11S-7S aggregates. Similar to aggregates formed by 11S or 7S alone, the gelation process of 11S-7S aggregates follows the time-temperature superposition principle. However, the gelation of 11S-7S aggregates consistently occurs earlier than that of mixtures of 11S and 7S aggregates. The 11S-7S aggregates exhibit a gelation pattern closer to that of 11S gels, where entropy plays a dominant role (ΔH*<-T av ΔS*), while the gelation of systems containing mixtures of 7S or 11S aggregates is primarily enthalpy-driven. These findings provide an energy-based explanation for the roles and mechanisms of different aggregates during the gelation of soybean protein systems, offering insights for regulating the processing quality of soy protein products. • An intermediate state forms during soy protein thermal denaturation. • The thermal denaturation of 7S and 11S conforms to the "shell-zipper" model. • The 11S/7S ratio regulates gelation initiation and rate. • The gelation of 11S-7S protein aggregates is primarily driven by entropy increase. • The gelation of 7S or 11S individual aggregates in mixed systems is enthalpy-dominated.