Insights into the cooling rate and preservative effect of slurry ice on large yellow croaker (Pseudosciaena crocea) in terms of the fish/ice ratio, salinity, and the ice mass fraction

The cooling effect of slurry ice as cooling medium on large yellow croaker (Pseudosciaena crocea) was studied by considering different fish/ice ratio, salinity and initial ice mass fraction (40%, 60%, and 80%). Results obtained with optical microscope clarified that the ice particle size and cooling time of slurry ice were decreased at increasing salinity. Best precooling efficiency was obtained with specific values of fish/ice ratio 1:2, salinity 5.0%, and initial ice mass fraction 60%. Then, the effects of precooling time (0, 3, 12, and 24 h) in slurry ice on the quality of large yellow croaker stored at 4°C were investigated. The results showed that slurry ice precooling could significantly (p < 0.05) inhibit the microbial reproduction and retard the quality deterioration of large yellow croaker. Therefore, slurry ice can be a promising precooling method for the quality maintenance of marine fish.

Practical applications

Large yellow croaker is extremely perishable due to its nutrient abundance. The spoilage process of fish is vitally influenced by the changes of internal environment and external environment after harvest. Timely precooling can prominently improve the shelf-life of perishable foods. Slurry ice, a two-phase system consisting of seawater (or artificial seawater) and spherical ice microcrystals, is regarded as an alternative precooling medium. Compared with conventional ice, slurry ice has faster cooling rate, little physical damage to soft tissue such as aquatic products and has better fluidity allows it to comprehensively cover the fish surface, thereby protecting fish from oxidation.