Effect of drying methods on molecular properties and functionalities of disulfide bond‐cleaved soy proteins

Effects of drying methods on hydrophobicity, solubility, water hydration capacity, viscosity, and adhesive strength of soy protein isolates treated with Na 2 SO 3 (disulfide bond‐cleaving agent) were investigated. Treatment with 0.1 M Na 2 SO 3 resulted in 28% decrease in disulfide linkages in soy proteins. While hydrophobicity and solubility increased, waterholding capacity of soy proteins decreased due to the treatment. Spray‐dried product had higher hydrophobicity, solubility, water hydration capacity, and viscosity compared to freeze‐dried product. Adhesive strength on wood increased due to modification; however, the drying process had no significant effect on this property. Viscosities of spray‐dried product, freeze‐dried product, and unmodified soy proteins were 2,200, 100, and 240 cP, respectively. Fluorescence spectra of spray‐dried and freezedried products indicated a partial folding of molecules around tryptophan. High‐performance liquid chromatographic elution profiles showed no significant differences in molecular sizes of unfolded molecules of spray‐dried and freeze‐dried proteins.