Transfer of animal DNA from substrate to Hermetia illucens and Tenebrio molitor larvae and impact of fasting on residue contents

Insect farming offers a sustainable alternative for protein production, yet EU regulations prohibit the use of food waste containing meat due to concerns about disease transmission. This study examined the transfer of animal DNA from substrates containing beef, pork, and chicken meat to black soldier fly larvae (BSFL; Hermetia illucens (L.)) and yellow mealworms ( Tenebrio molitor (L.)). The effect of fasting as a mitigation strategy was also evaluated. Larvae were reared on substrates containing 0, 3, 15 or 30% mixed meat consisting of equal parts of beef, pork, and chicken meat. The BSFL did not retain detectable animal DNA from any substrates. By contrast, yellow mealworms retained DNA from all meat types at 15 and 30% inclusion in the substrate, and porcine DNA at 3% inclusion. Fasting for up to 72 h after exposure to 30% meat did not eliminate animal DNA in mealworms and further confirmed the absence of animal DNA in BSFL from the start of fasting. Fasting reduced BSFL mass but did not affect the mass of mealworms. BSFL had higher mass gain at higher substrate meat inclusion, while higher meat inclusion resulted in lower mass gain in mealworms. Our findings thus highlight species-specific differences in meat-associated growth, DNA retention in larvae, and fasting effects between the two species. While mealworms should not be used in food systems that require avoidance of animal-derived genetic material for safety purposes, BSFL appear safe to use as DNA was not detected in BSFL even directly after collection from the substrates.