The use of slurry ice, both alone and in combination with ozone, as compared with traditional flake ice was investigated as a new refrigeration system for the storage of sardine (Sardina pilchardus). Microbiological, chemical and sensory analyses were carried out throughout a storage period of 22 days. According to sensory analyses, sardine specimens stored in ozonised slurry ice had a shelf life of 19 days, while counterpart batches stored in slurry ice or flake ice had shelf lives of 15 and 8 days, respectively. Storage in ozonised slurry ice led to significantly lower counts of aerobic mesophiles, psychrotrophic bacteria, anaerobes, coliforms, and both lipolytic and proteolytic microorganisms in sardine muscle, and of surface counts of mesophiles and psychrotrophic bacteria in sardine skin as compared with the slurry ice and the flake ice batches. In all cases, the slurry ice batch also exhibited significantly lower microbial counts, both in muscle and skin, than the flake ice batch. Chemical parameters revealed that the use of slurry ice slowed down the formation of TVB-N and TMA-N to a significant extent in comparison with storage in flake ice, the evolution of TMA-N being the most adequate parameter to detect quality losses. A combination of slurry ice with ozone also allowed a better control of pH and TMA-N formation as compared with slurry ice alone. Proteus vulgaris and Staphylococcus sciuri were identified as the main spoilers of sardine muscle. This work demonstrates that the combined use of slurry ice and ozone for the storage of sardine is can be recommended to improve the quality and extend the shelf life of this fish species.

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.

Slurry ice is a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature. Its employment was evaluated in the present work as a new chilled storage method for whole horse mackerel (Trachurus trachurus) and compared with traditional flake icing. Different chemical analyses (nucleotide degradation, lipid hydrolysis and oxidation, interaction compounds formation and electrophoretic protein profiles) related to quality loss were checked and compared to sensory evaluation. An inhibitory effect on quality loss mechanisms was observed for the slurry ice treatment, according to the assessment of the K value, free fatty acid content, thiobarbituric acid index, fluorescent compounds formation and sarcoplasmic protein profiles. The sensory analysis showed a higher shelf-life time for fish treated under slurry icing when compared with flake iced fish (15 days and 5 days, respectively). Results confirm the practical advantages of using slurry ice as a chilling storage method. According to the inhibition of lipid hydrolysis and oxidation obtained, the employment of slurry ice on relatively fat fish species is recommended to obtain safer and higher quality fish products.

Slurry ice, a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature, was evaluated as a new chilled storage method for whole European hake (Merluccius merluccius), a gadoid fish species of remarkable commercial interest, and this method was compared with a control batch stored for 19 days in traditional flake ice. The results obtained in the sensory analysis indicated a significant extension of shelf-life -from 5 days (flake ice batch) to 12 days (slurry ice batch) -in the latter batch, mainly deriving from a better maintenance of both external and fresh odour, the appearance of the gills and consistency. The slurry ice batch exhibited a significantly lower increase in pH as compared to the flake ice batch, this indicating a better control of the former over alkalinising microflora. Thus, significantly lower counts of total aerobes and proteolytic bacteria were also attained in hake muscle stored in slurry ice, microbial numbers reaching average differences of %1 log unit before 12 days of storage and above 2 or 3 log units, respectively, when this period was extended up to 19 days. The formation of total volatile basenitrogen and trimethylamine were also significantly lower in the slurry ice batch after 12 days of storage. According to the parameters assessed, storage of European hake in slurry ice extends the shelf-life of this species and allows a better maintenance of sensory and microbiological quality.

Effect of advanced chilling methods on lipid damage during sardine (Sardina pilchardus) storageSlurry ice is a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature. Its effect on lipid damage (hydrolysis and oxidation) was evaluated during the chilled storage of a fatty fish species, sardine (Sardina pilchardus). Slurry ice treatment was checked alone and in combination with ozone and compared to traditional flake icing during a 22-day storage. Different lipid damage indices (free fatty acids, FFA; peroxide value, PV; thiobarbituric acid index, TBA-i; fluorescent compounds, FR) were checked and compared to sensory assessment and nucleotide degradation (K value). According to lipid hydrolysis (FFA) and oxidation (PV and FR) developments, slurry ice showed an inhibitory effect (p ,0.05) on lipid damage during storage, as well as an inhibition of nucleotide autolytic degradation. Ozonised slurry ice did not provide differences (p .0.05) from slurry ice alone when considering lipid hydrolysis, nucleotide degradation and some lipid oxidation indices (PV and FR), although a higher (p ,0.05) TBA-i was observed at day 22 of storage when compared to flake ice and slurry ice treatments. However, a lower (p ,0.05) fluorescence development was observed for fish treated under ozonised slurry ice when compared to traditionally iced fish. Sensory assessment showed a higher shelf life for fish samples treated under ozonised slurry ice than for their counterparts under slurry ice (15 d versus 12 d), while flake icing led to a far shorter shelf life (5 d). According to sensory and biochemical (lipid matter and nucleotide) analysis, slurry ice has proved to be a promising technology for damage inhibition and quality retention in a fatty fish species such as sardine. Ozonised slurry ice was also shown to be useful, since a longer shelf life was obtained in the present experiment and a pro-oxidant effect of ozone on sardine lipids was not proved.