Mechanism for improving fermented soymilk gel through high-pressure homogenization: Regulating the structure of heat-induced protein aggregate.

Heat-induced aggregation of soybean protein (HIAP) during the preparation of soymilk results in poor texture, diminishes water-holding capacity and decreases the structural homogeneity of the fermented soymilk gel. Therefore, it is necessary to modify the HIAP to improve the texture of fermented soymilk gel. High-pressure homogenization (HPH) is an effective food processing technique and can potentially alter the HIAP conformation. A strain of lactic acid bacteria suitable for fermentation of soymilk was initially screened in this work. Subsequently, soymilk was treated with HPH to investigate the effect of the HPH treatment on HIAP and the gel structure after fermentation. The results demonstrated that HPH treatment led to a significant reduction in particle size (from 425.2 nm to 283.2 nm), protein dispersibility index, and zeta potential of HIAP. Additionally, the multispectral analysis revealed that the spatial structure of HIAP unfolded with increased content of β-sheet and a reduction in random coil in the secondary structure. Furthermore, the formation of a homogeneous and dense three-dimensional network structure of gel was prompted by an increase in hydrophobic interactions and disulfide bonds between the proteins, which not only enhanced the rheology and texture of the gel but also elevated its water-holding capacity from 45.4 % to 61.3 %. HPH treatment was demonstrated to be an effective method for regulating the structure of HIAP, thereby improving the texture of fermented soymilk gel. This study provides a theoretical foundation for developing processing techniques and industrial production of fermented soymilk.