Fatty acids profile of black soldier fly (Hermetia illucens): Influence of feeding substrate based on coffee-waste silverskin enriched with microalgae

The aim of this work was to find alternative low-cost and environmentally friendly rearing substrates for the growth of Hermetia illucens (HI) (Diptera, Stratiomydae), used as feed. At this purpose, insect feeding substrates based on the re-use of coffee silverskin, the main waste product of the coffee-roasting industry, enriched with various percentages of microalgae (i.e., Schizochytrium sp. or Isochrysis sp.), were tested. The fatty acid profile, as well as the relative amount of lipids, proteins and carbohydrates (these latter calculated as ratio to the total biomass of the sample) of ingredients, insect feeding substrates and HI prepupae, were determined for the first-time coupling Gas Chromatography-Mass Spectrometry and Fourier Transform Infrared Spectroscopy. A multivariate statistical analysis (Principal Component Analysis) was performed to better read into results. In general, the inclusion of microalgae caused in both feeding substrates and in HI prepupae an increase in the relative amount of lipids and proteins, improving their nutritional value. Higher amounts of unsaturated fatty acids, particularly of omega-3, and good nutritional indices were detected in HI prepupae reared on substrates enriched with 10%, 20% or 25% of Schizochytrium sp. with respect to HI prepupae fed with coffee silverskin enriched with Isochrysis sp., suggesting them as new nutraceutical ingredients for future functional feed and food. In addition, the substrate enriched with a 10% inclusion level of Schizochytrium sp. has to be considered the most convenient one since a greater inclusion of microalgae did not promote additional benefits in terms of nutritional value of HI prepupae.