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

Rice bran protein concentrate (RBPC) was hydrolysed by a commercial food grade enzyme-papain to get similar to 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 (alpha-helix and random coils) of rice bran protein hydrolysates (RBPHs) increased with an increase in DH. However, surface hydrophobicity (SHO), total beta-sheets, beta-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 beta-sheets content while inversely related to alpha-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 beta-sheets, beta-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.

Automated summary

Hydrolysis of rice bran protein concentrate by papain enzyme resulted in improved structural flexibility, antioxidant activity, and solubility of the protein hydrolysates, but decreased hydrophobicity and thermal properties. The study indicated that hydrolysis degree significantly affected the thermal, functional, and digestibility properties, with secondary structure and hydrophobicity playing important roles.