Study On The Protein Character And Gel Property Of Bighead Carp And Gaint Squid

Bighead carp(Aristichthys nobilis) and Gaint squid(Dosidicus gigas) are underutilized fish resources in China. Their protein characters and gel properties of bighead carp and gaint squid were studied in this paper.Physicochemical changes in Bighead carp surimi during frozen storage at -10℃,-20℃and -30℃were studied. Ca²⁺-ATPase activity and total–SH content of Bighead carp myofibrillar protein decreased during frozen storage, which decreased to 16.9%,64.1%,77.4%and 53.1%,60.2%,66.1% after 20 weeks of frozen storage. The decline in gel-forming ability was associated with the decrease in Ca²⁺-ATPase activity and total–SH content. Microstructural study revealed that the shape of ice crystal was different at different frozen temperature, which was the major reason of protein denaturation.Effect of enzymatic protein hydrolysates on denaturation of Bighead carp surimi during frozen storage was studied. Three protein hydrolysates were prepared from red drum(Sciaenops ocellatus) frame by three enzymes, which were Papain,Low-temperature Alkaline protease and Flavourzyme. Their major components and amino acid composition were analyzed. Bighead carp surimi containing 5%(w/w) protein hydrolysates was stored at -20℃. Salt solubility and Ca²⁺-ATPase activity of myofibrils and gel breaking strenth were measured during frozen storage. The structure of frozen samples were observed under scanning electron microscope(SEM). Their effects were compared with commercial cryoprotectant(4%sucrose, 4%sorbitol and 0.3%polyphosphate). The results showed that peptides were the major component of protein hydrolysates, which accounted for 82.12%～84.61%. The contant of protain was 13.14%～13.54%. Hydrophilic amino acids were the most abundant in the amino acid composition. Gly had the highest content, followed by Asp.