Evaluation of the potential of prepupae meal of black soldier fly (Hermetia illucens) as potential ingredient for rainbow trout (Oncorhynchus mykiss): effect on flesh quality

The decrease of global availability and high price of fishmeal have challenged industry to identify alternatives to this resource. Oncorhynchus mykissi is the leading cultured freshwater fish species in Europe and Hermetia illucens larvae are a high-value feed source. Therefore, the potential of defatted prepupae meal of H. illucens as potential ingredient for O. mykiss in final product quality was evaluated. Thus, was tested the effect of dietary fishmeal replacing levels (0, 25 and 50%) by prepupae meal of H. illucens in quality traits of O. mykiss flesh. Furthermore, the effect of storage time and cooking process in in quality traits of flesh of O. mykiss were also tested. Overall, results indicate that, irrespectively the dietary replacement level of fishmeal by H. illucens meal, no detrimental effects on morphometric, marketable and physical characteristics. Nonetheless, increasing inclusion of H. illucens meal led to an increase of cooking loss values, while proximate composition of raw and cooked fillet were not affected by the diet. Contrarily, flesh fatty acid profile, and consequently the quality indexes TI, AI, HH, PUFAn3/PUFAn6 and PUFA/SFA, were strongly affected by the substitution of fishmeal with insect meal. Saturated fatty acids increased with the inclusion of H. illucens, while MUFA and LCPUFA (particularly EPA and DHA) decreased with the inclusion of insect meal in the diet. The muscle lipid oxidation products decreased with the inclusion of H. illucens in the diet. The increase of the storage time had a negative effect on almost all tested variables. Overall, it can be concluded that the dietary fishmeal replacement by H. illucens up to 50% had little effect on the quality traits of rainbow trout. However, an increase of saturated and a decrease of MUFA and LC-PUFA were observed in muscle of fish fed the insect based diets, resulting in a decrease of lipid peroxidation.