脱脂豆粕预处理对大豆β-伴球蛋白结构的影响

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

摘要:

采用新鲜低温脱脂豆粕、干热处理脱脂豆粕和溶剂浸提脱脂豆粕为原料制备大豆β-伴球蛋白，研究低温脱脂豆粕预处理对制备大豆β-伴球蛋白结构的影响。新鲜低温脱脂豆粕制备大豆β-伴球蛋白羰基、游离巯基和总巯基含量分别为2.93 nmol/mg、1.39 nmol/mg和11.87 nmol/mg，干热处理脱脂豆粕制备大豆β-伴球蛋白羰基、游离巯基和总巯基含量分别为5.24 nmol/mg、0.41 nmol/mg和5.42 nmol/mg，溶剂浸提脱脂豆粕制备大豆β-伴球蛋白羰基、游离巯基和总巯基含量分别为1.85 nmol/mg、1.93 nmol/mg和15.64 nmol/mg，表明干热处理脱脂豆粕增加制备大豆β-伴球蛋白氧化程度，溶剂浸提脱脂豆粕降低制备大豆β-伴球蛋白氧化程度。随着蛋白质氧化程度的增加，大豆β-伴球蛋白二级结构中α-螺旋和β-折叠含量、表面疏水性和内源荧光强度下降，内源荧光最大吸收峰发生蓝移，并且伴随着蛋白质聚集体的出现，表明蛋白质氧化使得大豆β-伴球蛋白聚集。

Abstract:

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.