Fatty acid composition of Hermetia illucens larvae grown on different expired wet pet-food

The present study compared the effects of four different discarded pet foods (for cats) on Hermetia illucens fatty acid compositions of neutral (NL) and polar lipids (PL). We used: 1) broiler feed as a control diet (CTRL); 2) salmon mousse (SLM); 3) chicken mousse (CHK); 4) beef mousse (BF). Each diet was put into 9 plastic containers (n=9); each one had 2.5 kg of substrate and 1,200 five-day-old larvae. At 22 days old, larvae were separated from the frass, fasted for 24 hours, frozen, and then chemically analyzed. Total lipids (TL) were extracted, and then NL and PL were separated by solid-phase extraction. Each lipid fraction was methylated to obtain the fatty acid (FA) profile by gas-chromatography. A one-way ANOVA was run to highlight statistical differences. Results showed that SLM larvae had the highest TL content (26.17 g/100 g of dry matter). Saturated fatty acids (SFAs) prevailed over other FA categories, with a substrate effect observed. Specifically, BF, CHK, and SLM larvae had a lower content of SFAs and a higher content of monounsaturated FA (MUFAs) compared to the CTRL larvae. SFAs were preferentially stored in NL, while MUFAs were stored in PL. SLM pet food slightly enriched the larvae in n-3 polyunsaturated FAs, which were mainly stored in PL. In conclusion, Hermetia illucens can represent a promising avenue to avoid incineration or landfill disposal of waste, but emphasis on the accumulation site of essential fatty acids should be considered