EVALUATION OF AN OZONE- SLURRY ICE COMBINED REFRIGERATION SYSTEM FOR THE STORAGE OF FARMED TURBOT (Psetta maxima)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 The use of ozonised slurry ice was investigated as a new refrigeration system for the storage of farmed turbot (Psetta maxima), a non-fat fish species of high commercial value. With this purpose in mind, an ozone generator device was coupled to a slurry ice system working subzero at -1.5oC. The ozone concentration was adjusted to a 700 mV of redox potential, and the slurry ice biphasic mixture was prepared at a 40% ice/60% water ratio and a 3.3% of salinity. Microbiological, chemical and sensory analyses were carried out throughout a storage period of 35 days. Although certain biochemical parameters indicative of fish freshness –such as the rate of nucleotide degradation or TMA-N formation– were not significantly affected by the presence of ozone in the slurry ice mixture, storage in ozonised slurry ice significantly slowed down of mechanisms responsible for lipid hydrolysis –as determined by the release of free fatty acids– and lipid oxidation –evaluated by the peroxide value, the thiobarbituric acidindex and by the rate of browning reactions determined at 450/400 nm– in farmed turbot. Storage in ozonised slurry ice also led to significant (p<0.05) lower counts of both total aerobes and psychrotrophic bacteria in both turbot muscle and skin, as compared with the control batch stored without ozone. Sensory analyses confirmed an extended shelf life of turbot specimens stored in ozonised slurry ice, these maintaining “A” sensory quality up to day 14, while counterpart batch stored in slurry ice kept this quality only up to day 7. The combination of ozone and slurry ice may be recommended for the chilling and storage of farmed turbot with a view to extend its shelf-life.