Quality and shelf-life prediction for retail fresh hake (Merluccius merluccius).

Fish quality has a direct impact on market price and its accurate assessment and prediction are of main importance to set prices, increase competitiveness, resolve conflicts of interest and prevent food wastage due to conservative product shelf-life estimations. In this work we present a general methodology to derive predictive models of fish freshness under different storage conditions. The approach makes use of the theory of optimal experimental design, to maximize data information and in this way reduce the number of experiments. The resulting growth model for specific spoilage microorganisms in hake (Merluccius merluccius) is sufficiently informative to estimate quality sensory indexes under time-varying temperature profiles. In addition it incorporates quantitative information of the uncertainty induced by fish variability. The model has been employed to test the effect of factors such as fishing gear or evisceration, on fish spoilage and therefore fish quality. Results show no significant differences in terms of microbial growth between hake fished by long-line or bottom-set nets, within the implicit uncertainty of the model. Similar conclusions can be drawn for gutted and un-gutted hake along the experiment horizon. In addition, whenever there is the possibility to carry out the necessary experiments, this approach is sufficiently general to be used in other fish species and under different stress variables.

The use of water and ice with bactericide to prevent onboard and onshore spoilage of refrigerated megrim (Lepidorhombus whiffiagonis).

This study investigates the effectiveness of ozonated water and flake ice (combined Petfrost system) to increase the quality and stability of fresh megrim on fishing boats. The captured fish were washed, placed in plastic boxes, covered with flake ice and refrigerated at 2°C for up to 2-weeks onboard and, thereafter, for 11 days onshore. The experiments employed sterile, filtered and ozonated water at a concentration of 2ppm for washing the fish and making the flake ice. The results are compared with samples from a traditional treatment consisting of water and flake ice of marine origin. Fish were caught in four different hauls, which took 14, 12, 8 and 3 days in being landed. Subsequently, fish were stored for 1, 5, 7 and 11 days at 3°C. The different treatments were evaluated using sensory, microbiological and chemical techniques. Fish treated with ozone always showed the best quality. Megrim treated with ozone was still suitable for consumption after 14 days on board, and megrim stored for 12, 8 and 3 days on board could be stored for a further five days in the ice state once landed with an acceptable quality. In contrast, control fish were not suitable for consumption if stored for longer than three days on board.The results indicate that treatment with water and ice flakes made from sterile and ozonated water maintains the quality of fresh megrim onboard fishing boats and upon arrival onshore.

Possible role for cryostabilizers in preventing protein and lipid alterations in frozen-stored minced muscle of Atlantic mackerel.

Adding DE 18 maltodextrin (80 g kg(-1)) to high-fat minced mackerel was highly effective against lipid oxidation and protein and color changes during frozen storage. It increased the temperature of ice-melting onset (Tm') and decreased freeze concentration of solutes in the unfrozen water (UFW) phase, which would have allowed it to effectively slow such perturbations. This maltodextrin showed a higher effectiveness against lipid oxidation, but was slightly less effective in preventing the loss of protein solubility than common cryoprotectants, that is, an equiproportional mixture of sucrose and sorbitol. Such differences in effectiveness were much higher in low-fat minces, in which lipid oxidation proceeded to a much lower extent. Consequently, prior to replacing traditional cryoprotectants with maltodextrins, it should be known which processes limit the shelf life of the food. Decreasing (from 80 to 50 g kg(-1)) the proportion of maltodextrin added to high-fat minced mackerel showed that although it affected only slightly the effectiveness against lipid oxidation, it did notably affect the effectiveness in preventing the loss of protein solubility and color changes. Therefore, such a decrease could be accepted only if lipid oxidation is the most limiting process of shelf life, but does not seem appropriate when protein changes are important.

Modified method for the analysis of free fatty acids in fish.

The objective of this study was the development of a method for the quantification of free fatty acids (FFA) using less aggressive reactants against the handler and the environment than those used in the classic method of Lowry and Tinsley. The modified procedure is a variation of the Lowry and Tinsley method employing cyclohexane in place of benzene. The use of benzene is prohibited in certain work processes and laboratories, and the competent authority in each country is actively promoting research into harmless or less harmful products that could replace benzene. A comparison with the traditional AOCS titration method for oil analysis was performed. FFA content in mackerel frozen at -10 degrees C was measured according to the three methods over a 12 month period. The results showed similar values, and good correlations were obtained.