Effect of Defatted Soybean Flour Pretreatment on Structure of Soybean β-conglycinin

Fresh defatted soybean flour, dry heating of defatted soybean flour, and solvent extraction of defatted soybean flour were used as materials to prepare soybean β-conglycinin. Protein carbonyl, free sulphydryl, and total disulphide/sulphydryl content of β-conglycinin which prepared by fresh defatted soybean flour were 2.93 nmol/mg, 1.39 nmol/mg, and 11.87 nmol/mg, respectively; while those by dry heating of defatted soybean flour and solvent extraction of defatted soybean flour were separately 5.24 nmol/mg, 0.41 nmol/mg, 5.42 nmol/mg and 1.85 nmol/mg, 1.93 nmol/mg, 15.64 nmol/mg. The results indicated that dry heating of defatted soybean flour increased oxidation extent of soybean β-conglycinin, while solvent extraction of defatted soybean flour reduced oxidation extent of soybean β-conglycinin. As oxidation extent of soybean β-conglycinin prepared by three kinds of defatted soybean flour increased, the contents of α-helix and β-sheet, surface hydrophobicity, and intrinsic fluorescence intensity of soybean β-conglycinin decreased, and blue shift of the maximum emission wavelength were increased, accompanied by formation of protein aggregates, which indicated that protein oxidation resulted in aggregation of soybean β-conglycinin.