Black soldier fly (Hermetia illucens L.): effect on the fat integrity using different approaches to the killing of the prepupae

The increase of waste, due to the rise of the world population, renders the use of the black soldier fly (BSF; Hermetia illucens) as agri-food leftover biotransformer very attractive. Indeed, feeding on these substrates, BSF is capable of transforming them into valuable fat, proteins, and chitin. The present study is aimed at evaluating different approaches to the killing of the prepupae in order to assess which is associated with the lowest production of artefacts, notably free fatty acids. Folch extraction method, via an Ultra-Turrax homogeniser, was selected to isolate and analyse prepupal fat. The same method was also applied for a direct grinding method to kill black soldier fly prepupae. The integrity of fat originated from this direct grinding approach to the killing was compared in terms of fatty acid profile with the samples obtained with two other killing procedures, i.e. freezing and blanching. Direct grinding proved to be a better preservative of fat integrity in terms of lowest amount of free fatty acids (about 2.5%) in comparison with freezing (about 15%), but also with blanching (about 10%). Furthermore, the direct grinding is a killing strategy that reduces energetic demand and process time and helps lower analytical costs.