A synergistic enzymatic strategy of papain and transglutaminase to engineer the structure and texture of high-moisture plant-based meat analogs

This study developed a novel two-step enzymatic modification strategy involving papain hydrolysis followed by microbial transglutaminase (TGase) cross-linking to enhance the functionality of soy protein isolate (SPI) for high-moisture meat analogue (HMMA) production. By systematically optimizing the degree of hydrolysis (DH) and cross-linking conditions, it was found that moderate hydrolysis (DH = 3.56%) combined with TGase cross-linking (30 U/g) significantly improved the hydration and emulsifying properties of SPI. High-moisture extrusion of the modified SPI resulted in HMMA with a more ordered and anisotropic fibrous structure, as evidenced by a fibrous degree up to 1.86, an anisotropy index up to 1.68, enhanced hardness and springiness by 49.50% and 26.90%. These enhancements can be attributed to the rearrangement and covalent cross-linking of protein molecules, as well as the increased content of ordered structures such as β -folds and S-S bonds and improved water immobilization. Furthermore, the in vitro protein digestibility increased from 81.80% to 92.00% (enzymatic hydrolyzed groups) and 87.10% (enzymatic hydrolysis-cross-linking groups), indicating superior nutritional quality. These findings demonstrate that the synergistic "enzymatic hydrolysis-crosslinking" strategy effectively restructured SPI, providing a promising approach for producing plant-based meat alternatives with meat-like texture and enhanced performance.