Impacts of Killing Process on the Nutrient Content, Product Stability and In Vitro Digestibility of Black Soldier Fly (Hermetia illucens) Larvae Meals

The black soldier fly (BSF, Hermetia illucens) is considered a potential sustainable insect alternative source of protein for animal feed. The quality of a BSF meal is greatly influenced by the killing method and the purpose of this article is to compare the influences of different killing methods. BSFs at the 18-day-old prepupae stage were separated into six different killing methods with three replicates: 1. blending, 2. freezing, 3. CO2 treatment, 4. vacuum, 5. blanching and 6. CO2 plus blanching. After killing, BSF larvae meals were obtained by hot air oven drying and grinding. The chemical composition and in vitro digestibility calculated from sediments were not affected by the killing method, except that blending provided the worst BSF quality for all measured parameters (p < 0.05). The highest quality of BSF was obtained from the heat treatment procedures (blanching and the CO2 plus blanching methods), as they produced lower acidity after killing, total viable counts, browning reaction (enzymatic and non-enzymatic), darkness, moisture, fat acidity, protein and lipid oxidation during storage compared with other killing procedures (p < 0.05). Interestingly, the highest free amino acids in the supernatant after in vitro digestibility of BSF samples was observed with the CO2 plus blanching killing method (p < 0.05), whereas other parameters were similar to those obtained with blanching. The CO2 plus blanching method did not produce clearly different outcomes to blanching; therefore, the selection of one of these techniques over the other should depend on the regulations in each country.