Mechanism of gel network structure softening in soymilk fermentation of composite enzymolysis based on microscopic...

During fermentation, the proteins and lipids tend to form relatively coarse particle aggregates, resulting in hard textures and rough mouthfeel in soymilk gels. This study investigated the effects of protease, lipase, and composite enzymolysis on the gel network changes. Results indicated that composite enzymolysis with fermentation significantly reduced the particle size and firmness of soymilk gel compared to JM1, with increases in degree of hydrolysis (DH) and water holding capacity (WHC) by 24.25% and 4.62%, respectively. Molecular structure revealed that both enzymolysis and fermentation individually cause the unfolding of protein, transitioning the structure from a closed to partially open conformation; whereas the composite enzymolysis with fermentation exacerbated this phenomenon. Microstructure showed that combined enzymatic hydrolyzed proteins and lipids into smaller particles, which then recombined to form layered micelles. This transformation shifted the soymilk gel from a "particle" and "bead chain" protein polymer structure to a layered micelle structure during fermentation, altering the rigid texture typical of traditional soymilk gels, resulting in a softer and smoother soy yogurt.