The olive oil by-product in 'rainbow trout Onchorynchus mykyss (Walbaum)' farming: productive results and quality of the product

The aim of this work is to investigate olive oil byproduct [vegetation water (VW)] inclusion in rainbow trout diet and its e¡ect on the productive traits and the quality of the product. Two levels of VW inclusion were used and one control group was included. Fish diets were isonitrogeonous (crude protein 40%) and isoenergetic (18MJ kg DM). Two thousand and four hundred rainbow trout were used. An in vivo digestibility experiment was performed in order to determine diets digestibility. All the fish diets and ¢llets were analysed to determine the proximate and fatty acid composition. On final fish fillet, lipid oxidation was determined at 0, 24, 48,72,96 and192 h of storage using the 2-thiobarbituric acid method (thiobarbituric acid reactive substances). Aroma analyses on the final cooked and raw fillet were performed using an electronic nose. The VW inclusion partially reduced protein digestibility. The fish growth varied between 1.08% and 1.1% day. The supplemental level of VW led to a better antioxidant status of fish diet, in particular, in the fillet sample after 72 h of fillet conservation. Principal component analysis in raw and cooked fish fillet indicates that the VW inclusion in the fish diet led to aroma modification on fish fillet.