Effects of Lactic Acid Bacteria Fermentation on Antioxidant Activity and Solubility of Rice Bran Protein

In order to improve the poor water solubility of rice bran protein, fully demonstrate its biological activity, and expand its application in industries such as food, this article used rice bran protein powder as a raw material, first hydrolyzing rice bran protein with protease, and then fermented the rice bran protein hydrolysate with lactic acid bacteria to prepare products with high antioxidant activity. The results showed that the optimal enzymatic hydrolysis conditions were alcalase addition of 700 U/g, substrate concentration of 13% (w/v, calculated by protein), hydrolysis time of 3 h, hydrolysis pH of 8.5, and hydrolysis temperature of 60 ℃. The optimal fermentation condition was 2% (v/v, inoculation dose of 108 CFU/mL) of Lactobacillus plantarum 13110, initial pH of fermentation medium 5.5, fermentation temperature of 31 ℃, and fermentation time of 36 h. Compared with the enzymatic hydrolysate of rice bran protein, after fermentation by Lactobacillus plantarum 13110, the DPPH free radical scavenging rate of the fermentation broth increased from 36.12% to 57.42% (sample protein concentration of 1 mg/mL), the ABTS+ free radical scavenging rate increased from 76.27% to 90.35% (sample protein concentration of 0.5 mg/mL), and the peptide components with molecular weight less than 1.0 kDa increased from 0.67% to 6.84%. The solubility of rice bran protein was only 13.43% at pH7, while its solubility after enzymatic hydrolysis and fermentation was 72.12% and 85.38%, respectively. In summary, the synergistic fermentation of enzymes and bacteria can effectively improve the antioxidant activity and solubility of rice bran protein, providing technical support for the application of rice bran protein as a functional food substrate.