Cryoprotectants Reduce Protein Oxidation and Structure Deterioration Induced by Freeze-Thaw Cycles in Common Carp (Cyprinus carpio) Surimi

The objective of the present study was to investigate the effects of a cryoprotectant (a mixture of sucrose and sorbitol) on protein and lipid oxidation and structural changes in common carp (Cyprinus carpio) surimi subjected to different numbers of freeze-thaw (FT) cycles. Increased numbers of FT cycles were accompanied by increases in carbonyl content and thiobarbituric acid-reactive substances values and concomitant decreases in sulphydryl group (P<0.05) content, revealing that multiple FT cycles could cause protein and lipid oxidation in the carp tissue. Myofibrillar protein isolated from FT surimi also showed a reduced ATPase activity (P<0.05), increased hydrophobicity (P<0.05), and enhanced susceptibility to thermal aggregation. The addition of cryoprotectants significantly inhibited carbonyl formation and lipid oxidation (P<0.05), and its good protective effect on protein denaturation was demonstrated by its efficacy in maintaining Ca-ATPase activity, reducing the rapid exposure of hydrophobic and sulphydryl groups on the protein surface, and decreasing the degree of protein aggregation. Overall, the use of cryoprotectants reduced protein oxidation and structural deterioration induced by freeze-thaw in common carp surimi.