On-board quality preservation of megrim (Lepidorhombus whiffiagonis) by a novel ozonised-slurry ice system

The use of a combined ozonised-slurry ice system was investigated as a new refrigeration system for the on-board storage of megrim (Lepidorhombus whiffiagonis), a fish species that is usually stored aboard fishing vessels for 1 to 2 weeks. The time elapsed between the catch and unloading at the harbour affects its quality and commercial value directly. Microbiological, chemical and sensory analyses were carried out in megrim after 2 weeks of on-board storage in ozonised slurry ice, slurry ice or flake ice, and for an additional period of 6 days. Sensory analyses revealed that megrim specimens stored in ozonised slurry ice (oSI₆₀₀ batch) maintained A quality even after 20 days of storage, while counterpart batches stored in flake ice showed B quality at unloading, after 14 days of on-board storage. Storage in ozonised slurry ice (oSI₆₀₀ batch) also led to significantly (p<0.05) lower counts of aerobic mesophiles, psychrotrophic bacteria, Enterobacteriaceae and proteolytic microorganisms in megrim muscle as compared with flake ice. Biochemical analyses revealed that the use of ozonised-slurry ice or slurry ice alone slowed down the formation of total volatile base-nitrogen (TVB-N) and trimethylamine-nitrogen (TMA-N) in comparison with storage in flake ice, also allowing a better control of pH. Lipid hydrolysis and oxidation events also occurred at a lower rate in the ozonised-slurry ice and slurry ice batches than in the flake ice batch. The present study demonstrates that the combination of slurry ice and ozone for the on-board storage of megrim is advisable, thus improving the quality and extending the shelf life of this fish species.