Cryogenic vs. Mechanical freezing impact on the quality of the sea bass ( Dicentrarchus labrax ) during long-term storage

In this study, we compared the long-term impact of cryogenic and mechanical freezing on sea bass quality. Mechanical freezing (MF) and cryogenic freezing (CF) were conducted at -40 C-degrees and -80 C-degrees, respectively, with air velocities of 2 m s(-1) and 0.5 m s(-1) . Frozen samples were stored at -20 C-degrees for 60 days. We assessed quality attributes, including exudate loss, texture, TBA value, color, enthalpy, microstructure, and protein denaturation, over this period. Exudate loss increased significantly during storage, with no significant difference between freezing methods. The cutting force, L*, b*, chroma (C*), and total color difference ( Delta E) were mainly influenced by storage time rather than freezing methods, as p values were >0.05. MF samples were notably less green ( p < 0.05) than CF samples, as indicated by higher a* value. Lipid oxidation occurred post -freezing and during storage, with the TBA value at the 0th month being 11 % lower for cryogenic freezing compared to mechanical freezing, reducing to just 2 % after the 2nd month. CF exhibited slightly higher enthalpy than MF, although not significant. Furthermore, the deconvolution data suggested that protein denaturation was impacted not only by freezing storage but also by the freezing treatment and freezing methods to some extent. Microstructure analysis showed that CF produced smaller ice crystals and maintained tissue integrity (inter -fibre distance) better than MF ( p value = 0.000), a benefit that persisted during storage ( p value = 0.009). Overall, fish quality attributes were more affected by the freezing treatment and storage conditions than by the freezing methods.