Microwave Pretreatment of Soybeans Prior to Soaking Enhances Mechanical and Rehydration Properties of Yuba

Microwave pretreatment of native soybeans in the preparation of yuba remains underexplored, and the impact of this treatment on the resulting yuba quality is still unclear. In this study, soybeans were subjected to microwave pretreatment for 30–120 s before conventional soaking. CLSM revealed soybean microstructural changes, including cell-wall degradation and improved dispersion of proteins and lipids. FTIR and SDS-PAGE results of yuba indicated that hydrogen bond cleavage and the formation of new cross-links reduced protein coiling and polar group exposure, while stabilizing aliphatic chains, ultimately yielding a stronger and more compact yuba network structure. Mechanical and rehydration results further indicated that microwave treatment positively affected yuba quality. The 90 s pretreatment was identified as the optimal condition, exhibiting the highest elongation at break (126.36% increase) and rehydration capacity, along with improved color attributes, including higher lightness (L*) and yellowness (b*) values. These changes are likely attributable to disulfide-mediated protein reorganization, which creates greater spatial availability and thereby facilitates lipid incorporation. This study elucidates how microwave pretreatment drives the reorganization of soybean protein and lipid components, thereby influencing their distribution during film formation and providing a foundation for the tailored design of yuba with targeted mechanical properties.