Preparation of Silver Carp Scale Antifreeze Peptides and Its Improvement Effect on Gel Properties of Frozen-thawed Surimi

In this study, silver carp scale antifreeze peptides (ScAFPs) were prepared by enzymatic hydrolysis. Taking the freeze-thawing survival rate of Streptococcus thermophilus as the main index and the degree of hydrolysis as the auxiliary index, the optimal enzymolysis preparation process of ScAFPs was obtained through single factor and response surface optimization. At the same time, the basic properties of ScAFPs and their influence on the gel stability of surimi were studied. The results showed that the selected enzyme preparation was trypsin, substrate concentration of 5.0%, enzyme dosage of 3.8%, enzymolysis temperature of 37 ºC, enzymolysis time of 3.5 h. Under these conditions, the frozen survival rate of ScAFPs against Streptococcus thermophilus was 82.19%±1.03% and the degree of hydrolysis was 7.54%±0.43%. The relative molecular weight of ScAFPs was mainly in the range of 180~3000 Da, and its isoelectric point was around 4.2. Moreover, ScAFPs had strong hydrophilicity and good thermal stability, which could effectively reduce the ice crystal content in the system. The effect of ScAFPs on gel properties of freezing-thawing surimi showed that after five freezing-thawing cycles, the decrease of gel whiteness, hardness, chewiness and gel strength of surimi treated by ScAFPs was significantly (P<0.05) lower than that of surimi without cryoprotecter. When the addition of ScAFPs exceeded 2%, the freeze-thaw protection effect of ScAFPs on surimi was better than that of commercial antifreeze agents (4% sucrose and 4% sorbitol mixture). This study lays a theoretical foundation for the high-value utilization of silver carp scales and the application of ScAFPs as a new type of cryoprotectant in frozen surimi and its gel products.