Fatty acid composition of black soldier fly larvae

With an increasing world population and meat consumption the black soldier fly (BSF; Hermetia illucens) shows potential as feed for animals, while recycling nutrients from food waste. To produce larvae of high quality as animal feed, further understanding is needed of how the substrate affects the nutritional composition of the larvae. In this project the aim was to investigate how the chemical composition of the substrate affects the one of the larvae, with focus on fatty acids. The chemical composition of BSF larvae (BSFL) reared on six different substrates was investigated: 1)retaken bread, 2) rainbow trout, 3) food waste, 4) fresh mussels, 5) ensiled mussels and 6) rancid mussels. Significant differences were recorded in proximate and fatty acid composition between larvae reared on different substrates, especially in the crude fat and ash content. Linear regression analysis indicated mainly the carbohydrate, crude protein and ash content of the substrate affected the proximate composition of the larvae. The proportion of saturated fatty acids (SFA), especially lauric acid, increased in the larvae with an increased larval weight, while mono- and polyunsaturated fatty acids decreased. The main factor for finding omega-3 fatty acids in the larvae was the concentrations of these fatty acids in the substrate. The analysis of malondialdehyde concentration in the substrates did not produce reliable results for the samples analysed. While the high SFA content in the larvae could be problematic in aquaculture, the use of substrates such as mussels and fish could improve the quality of the BSFL as a feed alternative.