Effect of γ-irradiation on the physicochemical properties of soy protein isolate films

To elucidate the effect of γ-irradiation on the physicochemical properties of soy protein isolate (SPI) films, the molecular and mechanical properties of the films were examined after γ-irradiation of the film forming solution at various radiation doses. Gamma-irradiation of SPI solutions caused the disruption of the ordered structure of the soy protein molecules, as well as degradation, cross-linking, and aggregation of the polypeptide chains based on a SDS-PAGE study. Gamma-irradiation decreased the viscosity due to cleavage of the polypeptide chains. Alteration of soy protein molecules by radiation decreased water vapor permeability by 13%. Mean tensile strength of the SPI films increased two times by γ-irradiation. Measurement of Hunter color values indicated that radiation affected yellow color, resulting in a significant increase in Hunter +b values. Microstructure observed by scanning electron microscope showed that irradiated SPI films had a smoother and glossy surface than the control film.