Lipid profile and growth of black soldier flies (Hermetia illucens, Stratiomyidae) reared on by-products from different food chains.

Background: The total amount of bio-waste produced annually in the EU by the food and beverage chains is estimated at 37 billion kg. The use of insects for the valorization of by-products from these value chains may represent a sustainable solution. This study aimed to investigate the by-products obtained from different food chains and used for the rearing of black soldier fly (BSF) prepupae, and to evaluate the content and profile of the lipid extracted from the prepupae and outline its possible applications. The substrates used in this experiment were: (i) industrial by-products (brewery spent grains, cows' milk whey, grape stalks, and tomato peels and seeds) and (ii) by-products from retailers (bread dough, fish scraps, and spent coffee ground). Fat extracted from prepupae using an adjusted Folch method was used for total lipid content and fatty acid profile.

Results: The best larval performances were obtained from beer (0.22 g per prepupa), tomato (0.19 g per prepupa), and cheese (0.14 g per prepupa) food-chain by-products. The extremely different compositions of the substrates were reflected in the differentiated lipid profile of the BSF prepupae and in the range of ratios between unsaturated and saturated fatty acids, which varied from 0.37 for cows' milk whey to 1.34 for tomato peels and seeds.

Conclusion: The lipids, proteins, and chitin extracted from prepupae are high-value bio-based products that could be used in the feed / food industry or for the development of innovative biomaterials, such as biodiesel. These results suggest that food-chain by-products are the best candidates for insect-bioconversion purposes. © 2020 Society of Chemical Industry.