Feed insects for aquaculture: use of Hermetia illucens L. meal for Sparus aurata L.: chemical and microbiological characterization of the diets

The use of the Hermetia illucens meal (HIM), as an ingredient in feed, represents a way to achieve more sustainable production of food. Under the current regulation in Europe (2017/893), the use of HIM is permitted mainly within aquaculture. The aim was to characterize the chemical and microbiological composition of diets for Spaurus aurata L. containing HIM in partial substitution of fishmeal (FM). Four diets containing increasing levels of HIM (HIM0, HIM25, HIM35 and HIM50) with 0%, 25%, 35% and 50% of FM replacement, corresponding to an inclusion level of 0, 7.9%, 11% and 15.7% of HIM, respectively, were analyzed. Experimental diets, formulated to meet the Spaurus aurata requirements, were isoenergetic (22 MJ/kg gross energy) and isoproteic (42.7 g/100 g, as fed). Fatty acids composition was determined by gas chromatography. Mineral content, including the potentially toxic ones, was assessed via ICP-MS. Microbial flora was characterized following the ISO test methods. Data were analyzed using a one-factor ANOVA of XLSTAT statistical package. No significant difference for fatty acid profile, Atherogenic, Thrombogenic and Peroxidation indices was observed among the diets. The hypocholesterolemic:hypercholesterolaemic fatty acid ratio (H/H) showed the best significant (p < .05) values in the diets containing HIM. Twenty-six minerals were identified, nine of these showed significant differences among the diets (Hg, Na, Mg, Al, K, Ti, Mn, Zn, Sr). Hg content showed significant (p < .05) lower values (0.04 ppm) in the HIM35 and HIM50 than those observed in HIM0 and HIM25 (0.1 ppm) diets; however, the Hg values were below the limit value provided by the EU regulation (2015/186). The microbiological analysis showed good microbiological quality and no significant difference of each microbiological parameter was observed among the diets. The counts of the aerobic colonies were lower than 70 CFU/g, Enterobacteriaceae and coliforms charges were <10 CFU/g, while <100 CFU/g for yeasts and moulds. No Salmonella spp., L. monocytogenes and Clostridium spp. were detected. The HIM inclusion did not affect the fatty acid composition and the microbiological quality and positively influenced the H/H ratio and lowered the Hg content of the diets. Analyzes on the effect of dietary HIM inclusion on S. aurata performance and quality traits are carrying out.