Cryoprotective effect of collagen hydrolysates from squid skin on frozen shrimp and characterizations of its antifreeze peptides

The cryoprotective effect of collagen hydrolysates from squid skin (CH-SS) on shrimp muscle was investigated during the freeze-thaw cycles, and the antifreeze peptides (AFPs) in CH-SS were separated and identified. The results showed that CH-SS generated by acid protease had the highest antifreeze activity. It was further found that CH-SS showed an inhibitory effect on the denaturation and structural changes of myofibrillar protein during the freeze-thaw cycles, and partially retained the ability to bind water. SEM analysis indicated that CH-SS could effectively reduce the mechanical injury caused by ice crystals to shrimp muscle. The fraction with the highest antifreeze activity from CH-SS was obtained by Sephadex G-25 chromatography, and its main amino acid sequence was identified as DVRGAEGSAGL by the UPLC-MS analysis. This study provides a theoretical basis for the intensive processing of squid skin and the development of new antifreeze agents.