Future food: Decipher the microbiological safety of insect larvae and the link with the rearing substrate!

The use of insects as alternative protein sources is a promising strategy for meeting societal, nutritional and economic challenges. Among candidate species, the black soldier fly Hermetia illucens offers interesting nutritional properties. However, a better understanding of the microbial quality of the rearing substrate and greater microbial knowledge are needed for these insect-based foods.

An in-depth study:
It was against this backdrop that Lenaïg Brulé and her colleagues at SECALIM carried out an in-depth study of the microbiological quality of Hermetia illucens larvae, in collaboration with French breeders.
The project combined a systematic analysis of available data with experiments carried out on different types of rearing substrate, including classic options authorized by EU regulations (cereals, fruit, vegetables) and unauthorized options (co-products, end-of-life feed, and meat).
Revealing results:
A total of 1,012 sample results were collected and analyzed during this study, with native substrate, larvae and frass as sample types. Indicators such as total mesophilic flora, spores, lactic acid bacteria, yeasts/molds, as well as the major pathogens used in human food, were tested according to current standards (Clostridium perfringens, Bacillus cereus, Listeria monocytogenes, Salmonella spp., Escherichia coli, Cronobacter spp.). These data revealed a high microbial load of larvae potentially transmitted by the substrate. The main pathogenic bacteria identified were Bacillus cereus, Clostridium perfringens, Cronobacter spp, Escherichia coli, Salmonella spp and coagulase-positive Staphylococcus aureus, while Campylobacter spp and Listeria monocytogenes were not detected.
Main conclusions:
This study confirms the importance of adding a microbial inactivation treatment step during larvae processing, and of controlling the risks associated with pathogenic bacteria (notably Bacillus cereus, Clostridium perfringens and Cronobacter spp.) along the farm-to-fork chain. The results obtained will guide the definition of control criteria and optimize manufacturing steps to offer safe, sustainable products.