Abstract:Rice bran soluble dietary fibers (SDF) were obtained from rice bran by extrusion, fermentation with Rhizopus oryzae, and fermentation-extrusion. The microstructure, absorption peak characteristics, molecular weight, and monosaccharide composition of the rice bran SDFs were examined, and their antioxidant activities evaluated. The three processing methods significantly increased the SDF content to 51.49%, 108.63%, and 118.15% as compared to unprocessed SDF. Additionally, there was an increase in the number of porous microstructures observed following processing, along with a decrease in molecular weight. The four types of rice bran SDFs exhibited similar characteristic absorption peaks, but at different intensities. Compared to the unprocessed rice bran SDFs, SDFs prepared by fermentation and fermentation-extrusion contained structural fucose fragments and had higher rhamnose, arabinose, xylose, mannose, and galactose content. Meanwhile, a higher glucose content was observed in the extruded rice bran SDFs. Both extruded and fermented SDFs exhibit improved antioxidant activities, while no change was observed in the fermentation-extrusion-generated SDFs in terms of antioxidant activity. Comprehensive comparison revealed that SDFs prepared from these three processing methods had significant structural differences and enhanced antioxidant activity as compared to SDFs from unprocessed bran. Fermentation had the most significant effect on the SDFs. This study is of significance in developing new rice bran processing technology for the preparation of highly active rice bran SDFs.
