Effect of rice bran rancidity on the structural characteristics and rheological properties of rice bran protein fibril aggregates

Rice bran protein (RBP) was isolated from rice bran (RB) with different storage time and rice bran protein fibril aggregates (RBPFAs) were prepared by heating (90 °C) under acidic condition (pH 2.0) to investigate the effects of RB rancidity on the structural characteristics and rheological properties of RBPFAs. The results showed that the optimal RBP concentration for the preparation of RBPFAs was 40 mg/mL. As the heating time increased, the thioflavin T intensity, β-sheet content, average particle size, ζ-potential, and surface hydrophobicity of RBPFAs firstly significantly increased and then decreased (P < 0.05). When the heating time remained constant, the thioflavin T intensity, β-sheet content, ζ-potential, and surface hydrophobicity of RBPFAs significantly decreased with increasing the RB storage days from 0 to 10 d, while the average particle size significantly increased (P < 0.05). When heated for 8 h, the thioflavin T intensity of RBPFAs decreased from 1027.86 to 521.06 with increasing RB storage time, while the average particle size increased from 976.55 nm to 1285.50 nm. The viscosity, storage modulus (G′) and loss modulus (G’’) of RBPFAs gradually increased with the increase of RBP oxidation degree and heating time. Furthermore, the average particle size of RBPFAs was significantly correlated with their rheological properties (P < 0.05). Overall, RBP oxidative aggregation induced by RB rancidity inhibited the formation of RBPFAs, but enhanced their rheological properties. This study was instructive for the development and application of RBPFAs.