How does soybean protein isolate clusters modulate the structure and reversibility of heat-induced gelation of
Teng Cao1, Haijie Zhang1, Yiwen Liu2
1College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, China.
Abstract:
Thermoreversible methylcellulose (MC) is frequently combined with soybean protein isolate (SPI) to modulate gelation behavior for food applications. However, the role of SPI clusters in regulating MC gelation, particularly under repeated thermal processing conditions, remains insufficiently understood. To address this gap, light scattering, oscillatory rheology, and interfacial tension measurements was employed to systematically monitor molecular aggregation, gel formation, and thermal reversibility. Non-equilibrium structural transitions were captured using heating-cooling cycles and isothermal holding protocols. MC exhibited a two-stage thermal assembly process, with an activation energy of approximately 245 kJ/mol. SPI exerted a concentration-dependent dual effect on MC assembly: low SPI concentrations promoted MC nucleation and accelerated early-stage aggregation, whereas high SPI concentrations impeded direct MC-MC interactions through steric hindrance, thereby reducing network strength. The critical entanglement concentration (Ce) of MC was ~0.68 wt%. Below Ce, SPI disrupted the fragile network structure and suppressed gel development; above Ce, SPI triggered network reorganization, resulting in a distinct "rise-drop-rebound" profile in the storage modulus during gelation. Thermal cycling experiments revealed that low SPI levels (2.0 wt%) reduced hysteresis, while higher SPI concentrations (8.0 wt%) enhanced energy dissipation. Notably, all MC-SPI formulations exhibited thermal reversibility across multiple thermal cycles. Interfacial analysis indicated synergistic co-assembly of MC and SPI at 25 °C, along with improved retention of interfacial activity after thermal treatment. These findings elucidate the kinetic and structural mechanisms underlying MC-SPI co-assembly and provide a mechanistic framework for the rational design of thermoresponsive, high-strength biopolymer composites applicable to materials, food technology, biomedical engineering, and 3D printing.
