Effect of dietary black soldier fly larvae meal on fatty acid composition of lipids and sn-2 position of triglycerides of marketable size gilthead sea bream fillets

Insects are an alternative protein source recently adopted in aquacultured carnivorous species. However, the replacement of marine ingredients with insect meal might cut down the n 3 polyunsaturated fatty acid (PUFA) of fish fillet, a fraction of great interest for human nutrition. Recently, it has been shown that different animal species and the human species better absorb the dietary fatty acids esterified in the sn-2 position of the triglyceride (TG) than those contained in the sn-1 and sn-3 positions. Hence, the present paper aimed to evaluate in which extent replacing fishmeal with insect meal could alter not only the fillet fatty acid (FA) profile, but even the FA distribution inside the TGs. Specifically, three-hundred and sixty gilthead sea bream (Sparus aurata L.) were randomly divided into four groups with three replicates each. The fish were fed for 120 days four isoenergetic, isolipidic and isoproteic diets where fishmeal was substituted by Hermetia illucens (HI) larvae meal. The inclusion levels were 0% (HI0), 9.2% (HI9), 18.4% (HI18) and 27.6% (HI27), corresponding to 0, 25, 50 and 75% of fishmeal substitution, respectively. At the end of the trial, 10 fish per group were analyzed for marketable traits, fillet color values and lipid composition. Dietary intervention did not affect any of the considered marketable traits and the fillet color. Major changes were observed in the FA profile of the fillet lipids. The fillets from fish fed HI18 and HI27 contained the highest amount of saturated fatty acids while their n-3 PUFA were significantly reduced in comparison with HI0 and HI9. Analogous variations were observed in the FA composition of the TG fraction. On the contrary, dietary HI did not reduce the overall n-3 PUFA positioned in the sn-2 of TG, nor eicosapentaenoic acid (EPA) percentage. In conclusion, dietary HI inclusion did not substantially modify the presence of important fatty acids for human nutrition (i.e., EPA and DHA) in the sn-2 position of the fillet triglycerides, increasing the chances to be better assimilated and absorbed by humans.