Abstract:Peroxyl radicals were generated by the thermal decomposition of 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) under aerobic conditions in this study and served as a representative free radical derived from lipoxygenase-induced lipid peroxidation of polyunsaturated fatty acids. The effects of the peroxyl radical on the properties and secondary structure of selenium-enriched soy isolate protein (SPI) were investigated. With increasing concentrations of AAPH, the results of Fourier transform infrared spectroscopy showed that the ?-helix, β-turn, and random coil content increased, while the β-sheet content decreased. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) patterns indicated that the subunits of SPI accumulated at the top of the stacking gel; protein solubility and the free sulfhydryl content of SPI decreased. Surface hydrophobicity, emulsifying activity, and emulsifying stability of SPI increased initially, but later decreased; the wavelength of the maximum emission (λmax) in the intrinsic fluorescence spectrum was gradually blue-shifted, and fluorescence intensity first increased then decreased. The selenium-enriched soy isolate protein was superior to ordinary soy isolate protein in terms of structure, distribution of subunits, properties, and other test indicators, which may be related to the high selenium content in selenium-enriched soy isolate protein, indicating its stronger antioxidant activity.
