Extraction and properties of glutinous rice bran protein obtained by the mild alkaline extraction for the bran combined with enzymatic treatment for the residues

Abstract

The mild alkali extraction combined with the enzymatic hydrolysis was explored to extract protein from glutinous rice bran in the study, and the function properties of the proteins were investigated. The mild alkali extraction of pH 5.0 and temperature 50°C was carried out firstly for the water-soluble protein extraction from the bran at the solid–liquid ratio of 1:10 (w/v) for 3.0 h, and the complex enzyme of cellulase and papain (7:3, w/w) were subsequently added to hydrolyze the residue for a better protein yield. After a mild proteolysis treatment under the conditions of enzyme addition 5.0%, pH 6.0, temperature 55°C and time 4.5 h, the final 90.2 ± 0.22% protein yield was obtained. It was interesting that the DPPH radical scavenging activity of the IC50 0.71 mg/ml was significantly improved, meanwhile, based on the combined extraction strategy, the protein solubility, emulsifying, and foaming properties were significantly enhanced in a wide range of pH environments. These results demonstrated that the mild alkali extraction combined with the enzymatic hydrolysis could be used in the glutinous rice bran protein extraction with high yield and good functionality, and the extracted protein could be potentially applied in food industry as nutraceutical ingredient or as the functional ingredient in the commercialized food products. Novelty impact statement Although the glutinous rice bran has an abundance of protein content, the protein has not been well extracted yet to be utilized in the food industry. Therefore, the proper procedure needs to be explored for glutinous rice bran protein extraction. The mild alkali combined with the enzymatic hydrolysis was firstly applied in the study, and the protein yield of glutinous rice bran protein was notably improved, furthermore, the antioxidant and function properties of glutinous rice bran protein also have been significantly increased because of the mild extraction and proteolysis.