Marta Bernárdez

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.

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.

Salmon in modified atmospheres using high- and low-barrier packaging materials

The effectiveness of packaging material on the shelf-life of fresh salmon (Salmo salar) derived from aquaculture has been studied using an atmosphere rich in carbon dioxide and low in oxygen (80% CO2, 5% O2, 15% N2). Multilayer materials with different permeability to the gases (with copolymers of ethylene-vinyl alcohol or of polyethylene) were used in the upper film and/or in the packaging tray. The effect of the material on the conservation of the salmon was determined on the basis of changes in the initial gas mixture and the quantification of chemical, microbiological, and sensory variables during storage. In general, the results show small differences between the two types of packaging and their influence on salmon conservation. The sensorial parameter mean values (color, odor, flavor and texture) were favorable to the low barrier material LB/LB at the end of the storage period (day 13) when the salmon in EVOH/LB was considered as rejected. Se ha estudiado la efectividad del material de envasado en la vida útil de salmón (Salmo salar) fresco procedente de la acuicultura, utilizando una atmósfera rica en dióxido de carbono y baja en oxígeno (80% CO2, 5% O2, 15% N2). Los materiales multicapa con distinta permeabilidad a los gases (con copolímeros de etileno-alcohol vinílico o polietileno) se utilizaron en la película superior y/o en la bandeja de envasado. La valoración del efecto del material en la conservación del salmón se realizó de acuerdo a los cambios en la mezcla gaseosa inicial y a la cuantificación de variables químicas, microbiológicas y sensoriales durante el almacenamiento. En general, los resultados muestran pequeñas diferencias entre los dos tipos de envasados y su influencia en la conservación del salmón. Los valores medios de los parámetros sensoriales (color, olor, sabor y textura) fueron favorables al material de baja barrera LB/LB al final del periodo de almacenamiento (día 13), momento en que el salmón en EVOH/LB se consideró rechazado.