Fillet fatty acids and volatile organic compounds of Atlantic salmon fed diets including Hermetia illucens larvae

Aquaculture is expected to supply more than 65% of global fish production by 2030, thus increasing quantities of fish meal (FM) will be necessary as protein source in aquafeeds. However, the fish stocks (mainly anchovy and herrings) from which FM derives are nowadays overexploited. Hence, aquafeed production needs to be based on alternative protein sources. Among the other, insects are promising due to their fast growth, easy reproduction, few nutritional requirements and their ability to recycle organic waste. The present study tested the effects of the replacement of FM with partially defatted Hermetia illucens larva meal (HI) in the diet for seawater-phase Atlantic salmon (Salmo salar L.) on physico-chemical characteristics and consumer liking of fillets. Triplicate sea-cages of A. salmon were fed one of four isoproteic, isoenergetic and isolipidic diets for 16 weeks: a control diet (C, 0% of HI) and three diets with increasing substitution levels of FM with HI (33, 66 or 100%; IM33, IM66 and IM100, respectively). Then, fish were percussively slaughtered and filleted. Four salmon fillets from each sea-cage were allotted to physico-chemical analyses (n = 6) and consumers’ test (n = 6). The physico- chemical analyses included colour evaluation (Chroma Metre Cr-200, Tokyo, Japan), water holding capacity (WHC), texture profile analysis (Zwick Roell® texturometer, Zwick GmbH & Co. KG, Ulm, Germany), and proximate composition determination. A blind product test was performed with 80 consumers who evaluated on a 9-points scale the liking for appearance, odour, flavour, texture, and the overall judgement; they evaluated the adequacy of colour, texture, appearance, aroma, flavour and salty intensity, juiciness and fibrousness. Colour, WHC, texture and proximate composition were not affected by diet. Only IM66 group contained higher amount (p<.05) of protein than IM100 (20.92 and 19.48g/100g of fillets, respectively), while C and IM33 assumed intermediate values. Consumers’ liking was unaffected by the diet and received scores from 6 to 9. The main criticisms were related to the adequacy of colour and textural attributes. Indeed, IM100 group was considered the palest, the most fibrous and with the lowest aroma and flavour. Nevertheless, consumers highlighted their propensity to future consumption. To sum up, the inclusion of HI in diets for A. salmon determined physical modifications which were not instrumentally quantified, but which were perceived and accepted by consumers.