Protein hydrolysate from salmon frame debittered by plastein reaction: amino acid composition, characteristics and antioxidant activities

Summary Impacts of plastein reaction on bitterness, physicochemical and antioxidant properties of salmon frame hydrolysate with the aid of various proteases (alcalase and papain) at different concentrations and varying reaction temperatures were investigated. Plastein was produced from hydrolysate by papain at 40°C, which had 30% degree of hydrolysis (30DHP). Rearrangement of peptides in hydrolysate was performed by 1% papain at 40°C for 10 h, yielding plastein namely ‘30DHP‐P1’. It showed the lowest bitterness ( P < 0.05) than other plasteins and hydrolysates. Surface hydrophobicity was not related well with bitterness. Therefore, the size of peptides also determines the bitterness. 30DHP‐P1 had augmented solubility; however, its antioxidant activities (DPPH and ABTS radical scavenging activities and ferric reducing antioxidant power) were slightly lower ( P < 0.05) than those of hydrolysates. Bitterness of hydrolysate was markedly debittered via plastein reaction under optimal condition. Plastein generally had lighter colour and still possessed antioxidant activity.