Structural and functional modulation of rice protein hydrolysates: Influence of amylase pretreatment on extraction...

Hydrolysis has been widely used as an effective method to enhance the functional characteristics and biological activities of rice protein due to its green safety, mildness and controllability. This study was aimed to investigate the amino acid composition, structures and functions of rice protein hydrolysate (RPH) by three distinct methods: amylase-assisted hydrolysate (RPH-E), thermal & amylase-assisted hydrolysate (RPH-TE), and alkaline hydrolysate (RPH-A). The results demonstrated that RPH-A exhibited the superior protein content (79.54 ± 1.04 %), nitrogen recovery rate (72.70 ± 1.68 %), total color difference (16.85 ± 3.42) and browning index (21.07 ± 3.69). The antioxidant capacity of RPH-A was generally higher than that of RPH-E and RPH-TE. The emulsification ability, foamability and foam stability of the RPH-E and the RPH-TE were significantly higher than that of the RPH-A (p < 0.05), and the emulsification ability was further improved from 24.73 ± 2.25 % to 82.00 ± 2.06 % after ultrafiltration. RPH-E, RPH-TE, and RPH-A contained 27, 50, and 92 identified peptides, respectively, with 19 common peptides. These findings provide critical insights for the strategic selection of hydrolysis methods to tailor functional properties of rice protein ingredients in food applications.