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 Mtons. The possibility to use insects for the valorization of by‐products from these value chains may represent a sustainable solution. This study aims at investigating the by‐products obtained from different food chains for the rearing of black soldier fly prepupae to evaluate lipid content and profile and outline its possible applications. The substrates used in this experiment were: (i) industrial by‐products (brewery spent grains, cow's 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 utilized for total lipid content and fatty acids profile. RESULTS Best larval performances were obtained from beer (0.22 gweight per prepupa), tomato (0.19 gweight per prepupa), and cheese (0.14 gweight per prepupa) food‐chain by‐products. The extremely different composition of the substrate was reflected in the differentiated lipid profile of black soldier fly prepupae and in a range of ratios between unsaturated and saturated fatty acids comprised from 0.37 for cow's milk way to 1.34 for tomato peels and seeds. CONCLUSION The high content and type of lipids, together with the 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 candidate for insect‐bioconversion purposes.