Effect of Mildew and γ-Irradiation on the Physicochemical Property and Structure of Soybean Proteins
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Abstract:
Soybeans with different levels of mildew were prepared from fresh soybeans and then irradiated using cobalt-6060Co-γ rays. The effects of mildew and γ-irradiation on the in vitro digestibility, composition, and protein structure were investigated in terms of in vitro pepsin digestibility, amino acid composition, and results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) as well as Fourier transform infrared spectroscopy (FT-IR). The results indicated that mildew on soybeans reduced pepsin digestibility and total amino acid content by 23.74% and 2.07%, respectively, after 30 d culture. Moreover, the amount of β-turns and random coils increased by 2.67% and 4.14%, respectively, while the amount of α-helices and β-sheets decreased by 3.62% and 3.21%, respectively, in the secondary structure of soybean proteins. In fresh soybeans, γ irradiation had no significant effect (p > 0.05) on the amino acid composition, pepsin digestibility, and protein subunit composition within the dose range studied (10 to 30 kGy). However, a significant effect (p < 0.05) was observed on α-helices and β-sheets in the secondary structure of soybean proteins. On the other hand, in moldy soybean, γ irradiation resulted in a decrease in total amino acid content, a decrease in the amount of α-helices and β-sheets, as well as an increase in the amount of random coils in the secondary structure of soybean proteins.
