Abstract: The present study aimed to investigate the relationship between the structural, physicochemical and gelation properties of soybean 7S and 11S proteins. The secondary structures were explored by Fourier transform infrared (FT-IR) spectroscopy with Gaussian peak fitting. The fluorescent probe 1-anilino-naphthalene-8-sulfonate (ANS), Ellman’s reagent and a zeta potential meter were used to determine the surface hydrophobicity, sulfhydryl content and particle size of the proteins, respectively. The hardness, gumminess and springiness of the protein gels were analyzed with a texture analyzer. The results showed that the surface hydrophobicity decreased with increasing proportions of α-helix and β-sheet, but increased with increasing proportions of random coil and β-turn. Higher surface hydrophobicity was advantageous to the formation of gel network. The optimal gelation conditions for soybean 7S protein were determined as follows: protein concentration 0.12 g/mL, temperature 90 ℃, pH 6–8; and Na+ concentration 0.002 g/mL; and for 11S soybean: protein concentration 0.12 g/mL, temperature 95 ℃, pH 8–9, and Na+ concentration 0.002 g/mL. The secondary structures of the proteins determined their surface hydrophobicity, while the surface hydrophobicity affected the formation of gels. Meanwhile, the external factors of gel formation also affected the surface hydrophobicity of the proteins.

Key words: soybean 7S protein, soybean 11S protein, secondary structure, sulfhydryl, surface hydrophobicity, gelation properties