Effect of radio frequency treatment on functional, structural and thermal behaviors of protein isolates in rice bran.

To investigate the influence of radio frequency (RF) stabilization treatment on rice bran protein isolate (RBPI) properties, functional, structural and thermal behaviors of RBPI obtained from RF treated RB were evaluated under various temperatures between 80 and 120 °C holding for 5 min. The results showed that RF heating had negative impact on the yield, purity, foaming properties and solubility of RBPI when the treatment temperature was higher than 100 °C, while the absorption and emulsifying properties were improved. No significant changes were observed in primary structure of RF treated samples, but the second structure changed with an increase in random coil and a decrease in β-sheet, α-helix and β-turn. The decreased tryptophan fluorescence and increased surface hydrophobicity suggested alterations in tertiary structure. RF treatment also caused noticeable decrease in denaturation temperature and enthalpy of RBPI. The results would provide basic information for food applications of proteins isolated from RF stabilized RB.