Study of soybean gel induced by Lactobacillus plantarum: Protein structure and intermolecular interaction

The change of protein structure and intermolecular interaction during the formation of soy protein isolate (SPI) gel induced by Lactobacillus plantarum (L. plantarum) were investigated. In the present study, the peak value of UV–Vis spectra decreased gradually with the prolongation of fermentation time. Fermentation treatment resulted in α-helix content decreasing by 60.16%, while β-sheet content increased by 68.15% (P < 0.05). The surface hydrophobicity was decreased by 62.31% (P < 0.05) due to the molecular aggregation of SPI. Correspondingly, the free sulfydryl group content decreased by 58.48% (P < 0.05). These results highlighted that the protein structure and intermolecular interaction of SPI could be significantly changed by L. plantarum fermentation. The main intermolecular interactions maintaining the fermentation-induced gel were hydrophobic interactions and disulfide bonds. This work provided theoretical support for the establishment of the mechanism of fermentation-induced gel and the rational application of L. plantarum in soybean products.