Laccase-driven oxidative pre-modification improves soy protein thermal stability in high-protein systems

Demand for high-protein beverages is rising, yet the poor thermal stability of soy protein isolate (SPI) limits its application because processing induces aggregation and gelation. Here, a low-concentration pre-modification strategy combining preheating and laccase (LAC) was developed to improve SPI thermal stability. Preheating partially unfolded SPI and exposed buried aromatic residues, enhancing LAC-catalyzed oxidation and radical generation. This promoted intermolecular covalent crosslinking and produced more stable protein particles. LAC improved SPI thermal stability in a level- and time-dependent manner, as shown by weaker gelation and better flowability after reheating. Particle-size analysis showed that LAC promoted aggregation before reheating and that the resulting aggregates remained relatively stable afterward. Structural analyses further indicated that LAC-induced stabilization involved conformational rearrangement and strengthened non-covalent interactions. Overall, combining preheating with LAC provides an effective strategy for improving SPI thermal stability in high-protein systems.