关键词: 米糠蛋白, 有机酸, 酸沉, 结构特征

Abstract: In order to assess the effect of acid precipitation with different organic acids on the structure of rice bran protein, tartaric, malic, and citric acid were separately used to prepare rice bran protein at varying pH values (4.0, 3.5, 3.0, and 2.0) in comparison with hydrochloric acid as control. The results indicated that for each organic acid, total sulphydryl and α-helix content of rice bran protein did not significantly change with decreasing pH, whereas free sulphydryl and random coil content increased, β-sheet and β-turn content decreased and intrinsic fluorescence intensity and surface hydrophobicity firstly increased and then decreased. Total sulphydryl content, secondary structure composition and surface hydrophobicity of rice bran protein prepared with organic acids did not significantly differ from those of rice bran protein obtained with hydrochloric acid, whereas a decrease in free sulphydryl content was observed together with an increase in intrinsic fluorescence intensity. The results of molecular mass distribution, particle size distribution, and electrophoresis indicated that acid precipitation at low pH resulted in partial dissociation and aggregation of rice bran protein without leading to the formation of new subunits and high molecular weight aggregates.

Key words: rice bran protein, organic acid, acid precipitation, structural characteristics