Antioxidant and cryoprotective effects of hydrolysate from gill protein of bighead carp (Hypophthalmichthys nobilis) in preventing denaturation of frozen surimi

This work aimed to evaluate the efficacy of protein hydrolysates from bighead carp gill in inhibiting protein oxidation and quality loss in surimi. Firstly, antioxidant activity of hydrolysates in vitro was assessed, then 1%, 2% hydrolysates with better antioxidant activity and 4% sucrose were added to surimi respectively and stored at -18 °C for 4 months. Peptide sequences of above hydrolysates were also identified. The results suggested that hydrolysates of neutral protease had excellent 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability (42.93%) and Fe2+-chelating activity (73.27%). Compared with surimi without treatments, surimi with hydrolysates had higher sulfhydryl and salt-soluble protein concentrations, greater Ca2+-ATPase activity, lower disulfide bonds, carbonyls and hydrophobicity, as well as better gel strength and texture (p < 0.05). This study demonstrated that gill hydrolysate had antioxidant and dose-dependent cryoprotective effects on surimi that were comparable to the effects of sucrose, representing it as an alternative to sugar cryoprotectants in surimi industry.