Immersion frozen storage combined with silver carp muscle hydrolysate: Effects on freshness, protein properties and microstructure of cryopreserved grass carp

This study highlighted the combined effects of immersion frozen storage (IFS) and silver carp muscle hydrolysate (SCMH) on the quality of cryopreserved grass carp. The fish fillets were pretreated with SCMH and stored at −18 °C using an indirect IFS method (SCMH + IFS), which offered rapid freezing and reduced temperature fluctuations (±0.4 °C), and changes in freshness, protein properties and muscle structure were evaluated over a 60-day storage period. Compared to IFS alone or traditional air frozen storage (AFS), samples treated with SCMH + IFS showed lower increases in K value (from 10.4% to 33.9%), TVB-N (from 7.3 mg/100g to 15.1 mg/100g), as well as retarded changes in the solubility, Ca 2+ -ATPase activity, surface hydrophobicity, and sulfhydryl content of myofibrillar protein. Furthermore, the ice formation and recrystallization as well as the physical damages to fish muscle myofibril structure were markedly mitigated in the SCMH + IFS samples. Therefore, SCMH + IFS was a promising approach for enhancing the quality of cryopreserved fish products. • An immersion frozen storage (IFS) strategy is used to improve frozen fish quality. • IFS offers the advantages of rapid freezing and less temperature fluctuations. • Silver carp muscle hydrolysate (SCMH) further enhances the quality of IFS samples. • The combined application of SCMH and IFS is promising for fish cryopreservation.