Abstract: In the present study, the structural changes of soybean proteins in aqueous suspension of skimmed soybean meal after being fermented by Lactobacillus plantarum were studied. With the extension of fermentation time, the degree of hydrolysis and in vitro digestibility of fermented samples were increased, and the particle sizes of soluble proteins became smaller. These results indicated that soybean proteins were degraded to a certain degree after fermentation. Simultaneously, the molecular structure of proteins in fermented samples was further unfolded, resulting in an increase in beta-sheet content and a decrease in alpha-helix content, as compared to the original soybean proteins and those sterilized at 0 h of fermentation. A red shift in the wavelength of maximum fluorescence emission was observed for the fermented soybean proteins. More sulfhydryl groups were exposed after fermentation. In addition, scanning electron microscopy (SEM) analysis showed that the surface of fermented soybean proteins was not as smooth as that of the original ones, with corrosion pores appearing.

Key words: Lactobacillus plantarum, soybean meal, protein structure, fermentation