Enhancement on the solubility of polyploid and diploid rice proteins by enzymatic hydrolysis: From structural and functional characteristics of rice protein hydrolysates.

Polyploid rice protein (PRP) has the advantage of high nutritional value, but its functional properties are minimal due to its poor solubility. This work aims to improve the solubility of PRP through enzymatic hydrolysis and assess the effect of hydrolysis time (5-330 min) and protease type (Alcalase, Neutrase, and Trypsin) on the structural, functional, and antioxidant properties of PRP hydrolysates (PRPHs). Compared to PRP, PRPHs exhibited significantly decreased free sulfhydryl content and surface hydrophobicity and improved structural flexibility, regardless of the protease used. With increasing time, the nitrogen solubility index of the hydrolysates increased by 25.01 %, which was attributed to the reduction in molecular weight (< 15 kDa). The highest emulsifying activity (48.81 m/g) and hydroxyl radical scavenging activity (IC of 5.49 mg/mL) were observed from Neutrase hydrolysates at 210 min and 330 min, respectively. Trypsin hydrolysate at 210 min demonstrated the lowest IC (0.17 mg/mL) in ABTS. Moreover, compared to diploid rice protein hydrolysates (DRPHs) obtained under the same conditions, PRPHs by all proteases exhibited superior functional and antioxidant properties and richer amino acid content. This study showed the potential of PRPHs applied to functional foods with favorable functional and antioxidant properties.