Antioxidant activities of the fractionated protein hydrolysates from heat stable defatted rice bran



The hydrolysates from heat stable rice bran (HSDRB) treated by Alcalase 2.4L and Protease 500G were desalted and fractionated by hydrophobicity using a nonpolar, styrene divinylbenzene resin and macroporous adsorption resin DA201-C. The antioxidant activities of HSDRB hydrolysates (HSDRBH) eluted by 25%, 50%, 75% and 100% ethanol were investigated using 2, 2-di (4-tertoctylphenyl)-1-picrylhydrazyl free radical-scavenging activity assay, reducing power assay, ferrous ion-chelating activity assay and lipid peroxidation inhibition assay. The HSDRBH-75 had the highest reducing power assay and inhibition ratio of linoleic acid autoxidation, which might be associated with reduced molecular weight, amino acid composition and hydrophobicity. The highest metal-chelating activity of four different fractions (at the concentration of 4 mg mL−1) had a positive correlation (= 0.768, P = 0.116) with the total content of basic amino acid (Lys, Arg, and His) and a negative correlation (= −0.886, P = 0.057) with the range of molecular weight (Mw < 1000 Da). The HSDRBH-75 had the highest antioxidant activities in many assays, which suggests that it may become a good natural antioxidant as a food additive.