Effect of rice bran rancidity on the structure and antioxidant properties of rice bran soluble dietary fiber

The effects of storage time of fresh rice bran on the structure and antioxidant properties of rice bran soluble dietary fiber (RBSDF) were investigated. As the storage time of rice bran prolonged, a significant increase of acid value of rice bran crude oil was accompanied by a significant decrease of RBSDF yield (P < 0.05). The antioxidant properties of RBSDF first increased, and then decreased, which was accompanied by the formation of oxidized aggregates of RBSDF. The results of FT-IR and monosaccharide composition implied that hydroxyl oxidation was accompanied by changes in monosaccharide composition of RBSDF during storage of rice bran. As the storage time of rice bran increased, the content of free phenolics gradually increased, the content of bound and total phenolics first increased, and then decreased. The results of correlation analysis showed that among the factors affecting the antioxidant properties of RBSDF, the content of phenolics and soluble aggregates was more significant than monosaccharide composition. Overall, the structure and antioxidant properties of RBSDF were related to the degree of rice bran rancidity, suggesting that the degree of rice bran rancidity could be one of the potential means to regulate the antioxidant properties of RBSDF.