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Partial replacement of fish oil with vegetal oils in commercial diets: The effect on the quality of gilthead seabream (Sparus aurata)

Álvarez, A., R. Fontanillas, A. Hernández-Contreras and M. Hernández

The long-term unsustainability of fish oil as a lipid source in aquaculture feeds has led to its progressive replacement with vegetable oils. Several studies have shown that this replacement results in a different fatty acid profile that is likely to compromise the healthy properties and quality of fish by reducing their n-3 HUFA content. In the present study, we evaluate the effect of partial replacement of fish oil with vegetable oils on the quality of the final product. Eighty-four gilthead seabream (Sparus aurata) were fed one of two different commercial diets for 19 weeks in triplicate (14 fish per tank). These diets contained either 100 % fish oil (FO diet) or a 75 % vegetable oil blend (VO diet) (50/50 mixture of soybean and rapeseed oil). After slaughter, physical-chemical analyses (Fatty Acids (FAs); flesh color; Water-Holding Capacity (WHC); pH; and Texture Profile Analysis (TPA)) and a sensory analysis were performed. Fish fed either diet displayed similar growth and feed conversion rates (SGR and FCR). The fish fed the VO diet showed an increase in muscular n-6 fatty acids, which resulted in a lower n-3/n-6 ratio. A lower presence of EPA and DHA fatty acids was also observed, although the total quantity of n-3 fatty acids was similar in both groups. With regard to fat quality, the Atherogenic Index (AI) was lower in the VO-diet group, while both groups presented a similar Thrombogenic Index (TI). The diet had some effect on quality parameters, but the changes were not very intense. The differences observed in the a* and b* chromatic parameters were not significant, but a greater and significant color saturation in the vegetable oil group was observed. No significant differences in pH and WHC were observed. Fish fed the vegetal oil diet also scored higher for hardness, springiness, gumminess and chewiness. In the sensory analysis no significant differences were observed between the two groups.

The differences observed for both the fatty acid profile and the quality parameters do not appear to have any important implications in terms of either health or the sensory properties of gilthead seabream fed a vegetable oil diet.