El presente trabajo se ha centrado en el desarrollo de emulsiones alimentarias aceite-en-agua estabilizadas con proteínas de atún. Específicamente, se ha analizado la influencia del método de conservación de las proteínas aisladas (liofilización, congelación) y de las condiciones de procesado seleccionadas sobre el comportamiento reológico y la microestructura de dichas emulsiones. Se han preparado emulsiones aceite en agua (con un contenido del 70% en peso de aceite) estabilizadas con proteínas de atún. La concentración de emulsionante usada ha sido 0,50% en peso. El comportamiento reológico de estas emulsiones no depende significativamente del método de conservación de la proteína empleado. Por otra parte, un aumento de la velocidad de agitación durante el proceso de manufactura de la emulsión da lugar a una disminución continua del tamaño medio de gota y a un aumento de las funciones viscoelásticas dinámicas, menos significativo a medida que aumenta dicha velocidad de agitación. | This work is focused on the development of o/w salad dressing-type emulsions stabilized by tuna proteins. The influence of protein conservation methods after the extraction process (freezing or liofilization) on the rheological properties and microstructure of these emulsions was analyzed. Processing variables during emulsification were also evaluated. Stable emulsions with adequate rheological and microstructural characteristics were prepared using 70% oil and 0.50% tuna proteins. From the experimental results obtained, we may conclude that emulsion rheological properties are not significantly affected by the protein conservation method selected. On the contrary, an increase in homogenization speed favours an increase in the values of the linear viscoelastic functions. Less significant is the fact that as agitation speed increases further, mean droplet size steadily decreases.

This work deals with the manufacture of oil-in-water food emulsions stabilised by tuna proteins. The influence of protein and oil concentrations on the linear viscoelastic properties and microstructure of these emulsions was analysed. Stable emulsions with suitable linear viscoelastic response and microstructural characteristics were formulated with 70 wt.% oil and, at least, 0.25 wt.% tuna protein. Similarly, emulsions with oil concentrations between 45 and 70 wt.% were prepared using 0.50 wt.% protein. All these emulsions showed a predominantly elastic response in the linear viscoelastic region and a well-developed plateau region in its mechanical spectrum. Rheological and droplet size distribution results pointed out an extensive droplet flocculation, due to interactions among emulsifier molecules located at the oil–water interface of adjacent droplets. As a result, the linear viscoelastic behaviour was controlled by protein–protein interactions, allowing the use of the plateau modulus to successfully normalise both the storage and loss moduli as a function of frequency onto a master curve, irrespective of the selected emulsion formulation.

The dielectric properties of tylose water pastes during microwave thawing and heating were measured over 300–3000 MHz and −30 to +60 °C, and the feasibility of their use as a frozen model food instead of frozen lean tuna was evaluated. The effects of salt (NaCl) content (0.5–2.0%, wb) on the dielectric properties were investigated. Although salt is a good additive for increasing the dielectric loss factor, higher salt addition increased the thawing time and non-uniformity through decreased penetration depth. A similar response to increasing temperature between frozen lean tuna and tylose paste was observed during MW thawing and heating at 2450 MHz, due to similarities in penetration depth. This was possible by an appropriate adjustment of the dielectric properties of tylose by salt addition (0.5% NaCl). This study confirmed the potential of frozen tylose paste as a model food in evaluating performance of microwave thawing of real foods.

The Maltese Islands food-water-energy nexus faces substantial challenges. These include increasing levels of land fragmentation and abandonment, an aging farming population and decreasing returns possible for remaining, often part-time, farmers. Demand for high quality, locally produced vegetables and seafood from natives, tourists and migrants continues to increase while production shrinks in the context of a rich traditional food culture. The country’s aquaculture sector also faces serious obstacles with exports facing tough competition and the tuna fattening industry dwindling because of reduced quotas. Water resources are also very scarce. Malta has no lakes or rivers and ground water is becoming increasingly brackish because of over-extraction, In terms of water resources per inhabitant, Malta is the most water stressed country in Europe and one of the ten most water-short countries in the world. Domestic supply of water is highly dependent on desalinization – an energy intensive process. Moreover, 90% of groundwater is of poor status and unfit for drinking because of nitrate pollution. This paper uses Malta as a case study to scope the potential of aquaponics to meet the complex demands of an economy with a high standard of living but extreme water-scarcity. Aquaponics – a closed cycle, soil-less method of cultivating crops that is highly water efficient and can reuse the limited effluents from intensive fish culture as a nutrient source, is assessed.

This study aimed to evaluate the effects of alternative feed ingredients: Insect meal (DI) using non-defatted meal obtained from Acheta domesticus, Microalgae (DM) using a mix of four marine microalgae ((Nannochloropsis gaditana, Tisochrysis lutea, Rhodomonas lens, Isochrysis galbana), Protein and oil from water of tuna canning process (DP&L) and a Mixture (DMix) of the three ingredients, on the growth, feed utilisation, digestibility and composition of meagre juveniles, and the results obtained were compared with a feed similar to a commercial feed used as a control (DC). Results show that the formulated alternative feeds had different effects on fish growth. DMix have a similar growth performance than the control, whereas the other treatments (DI, DM and DP&L) showed a lower final weight. Hepatosomatic and viscerosomatic indices did not show differences among the treatments. Muscle protein content was higher for fish fed with DMix group whereas lipids were significantly higher in DI. In the case of the liver, protein was higher in the liver of fish fed with DI, DM and DP&L, whereas lipids were higher in fish fed with DI and DM, a result that was confirmed with the results obtained in hepatocyte size and lipid accumulation.The nutritional value of the meagre muscle at the end of the study showed that meagre fed with DM and DI diets contained a significantly higher content of monounsaturated and n-6 PUFA, whereas fish from the groups fed with DP&L and DMix had a significantly higher content of DHA and n-3 PUFA with the liver showing similar results. In view of the results obtained, the ingredients assayed in this study might be used as alternative sources of protein and lipids in aquafeeds since no negative effects were detected neither on fish growth, muscle composition or final nutritional value, except in the case of the diet with microalgae (DM), which inclusion rate in the feed must be adjusted and needs more research.