Abstract: The effects of different heat treatments (hot water bath, microwave heating and radio frequency heating) and final temperatures (70, 80 and 90 ℃) on physicochemical properties and structure of zein were investigated. The results showed that three heat treatments could enhance the water solubility, emulsifying capacity and free thiol content of zein, and the effect increased with the increase in final temperature. The solubility, emulsifying capacity and of free sulfhydryl content of radio frequency treated samples at final temperature of 90 ℃ were increased by 74.65%, 171.7% and 53.94%, respectively. By differential scanning calorimetry, it was found that protein denaturation temperature increased slightly after microwave treatment. Furthermore, ultraviolet spectroscopy showed that the unfolding of the protein molecule associated with group exposure was induced by microwave and radio frequency, which improved the solubility and emulsifying ability of the protein. Meanwhile, Fourier transform infrared spectroscopy showed that heat treatment altered the secondary structure of zein, and the effects of microwave and radio frequency treatment were more pronounced.

Key words: zein, protein denaturation, heat treatment, microwave, radio frequency