Enzymatic modification of rice bran protein: Impact on structural, antioxidant and functional properties

Abstract

Rice bran protein concentrate (RBPC) was hydrolysed by a commercial food grade enzyme-papain to get ~15%, 25% and 32% degree of hydrolysis (DH) to investigate its effect on structural, antioxidant and functional properties as well as in-vitro digestibility. Bulk density and structural flexibility (α-helix and random coils) of rice bran protein hydrolysates (RBPHs) increased with an increase in DH. However, surface hydrophobicity (SHO), total β-sheets, β-turns, and thermal properties decreased with increasing DH. RBPHs possessed improved antioxidant activity as compared to native protein, except metal chelating power. RBPHs had higher solubility and digestibility. Thermal properties were positively correlated with β-sheets content while inversely related to α-helix content. An inverse correlation was observed in protein solubility and SHO. Emulsion activity index and foaming stability were positively related to SHO. Protein digestibility was negatively correlated to the β-sheets, β-turns, and SHO. The results indicated that secondary structure and SHO are the primary factors in affecting the thermal and functional properties as well as digestibility. It is thus concluded that the enzymatic hydrolysis might be applicable for RBPC to increase its potential bioactivity but reserve partial interfacial properties.