Abstract:The physicochemical properties of acetylated rice protein, including solubility, surface charge, and secondary structure, were explored; the enzymatic hydrolysis of acetylated rice protein by trypsin was also investigated. The results showed that the isoelectric point (pI) of acetylated rice protein was decreased with increasing degrees of acetylation. Acetylation improved the solubility of rice protein, as it was increased to 0.7 mg/mL from 0.4 mg/mL (neutral pH) upon acetylation. Acetylation significantly increased the net negative surface charge of the protein, and a higher degree of acetylation led to an increased net negative charge. Meanwhile, acetylation also had certain effects on the secondary structure of rice protein. The α-helix and random coil contents remained the same, while the β-sheet content decreased and β-corner content increased upon acetylation. Acetylation enhanced the enzymatic hydrolysis rate and digestibility of rice protein by trypsin. When the substrate concentration was the same, the kinetic parameter increased with increasing degree of acylation. The electrophoresis results of the enzymatic hydrolysates showed that after enzymatic hydrolysis by trypsin for 120 min, bands at 20 kDa, 16.9 kDa, and 14 kDa were still clearly visible for the unmodified rice protein, while the bands corresponding to the acetylated rice protein almost completely disappeared.
