Influence of enzymatic hydrolysis conditions on the degree of hydrolysis and functional properties of protein hydrolysate obtained from Chinese sturgeon (Acipenser sinensis) by using papain enzyme

In this study, protein hydrolysate was prepared from the muscles of Chinese sturgeon (Acipenser sinensis). The effects of different conditions on the degree of hydrolysis (DH) by using papain were investigated. The DH of 24.89% was attained under the optimum conditions including solid-to-liquid mixing ratio of 1:1, enzyme–substrate ratio of 3%, pH 6, temperature of 70 °C, and incubation time of 6 h. The yield of protein hydrolysate was 17.47%, in which the protein content was 79.67% and amino acid content was 96.35%. The molecular weight of peptides decreased with the progress in hydrolysis time. Protein hydrolysate solubility ranged between 86.57% and 98.74%, emulsifying activity index was 11.0–13.27 m²/g, emulsion stability index was >94% at different pH levels, water holding capacity was 1.93 g water/g protein, oil holding capacity was 2.59 g oil/g protein, and foam capacity was 76.67%. The obtained fish protein hydrolysate contains improved functional properties and has potential applications in food industries.