Study Shows Food Allergens Can Carry Over From Insect Feed to Edible Insects
Edible insects reared on substrates containing food allergens may retain allergen residues even after a 48-hour pre-harvest fasting period, according to a recent study published in Foods. The findings highlighted the importance of considering rearing substrate composition when assessing the allergen safety and labeling of insect-based foods.
Researchers from the Experimental Zooprophylactic Institute of Piedmont, Liguria, and the Aosta Valley (IZSPLV) and the National Reference Center for the Detection of Food Allergens and Substances Causing Food Intolerance (CReNaRiA) in Italy investigated whether plant-derived allergens could carry over from insect feed into Hermetia illucens (black soldier fly) larvae.
The larvae were reared for 15 days on rice- and maize-based substrates containing 10 percent peanut, almond, soy, celery, or gluten. The 10 percent concentration was selected to represent a high-exposure, worst-case scenario. Researchers collected larvae at the end of feeding, after 24 hours of fasting, and after 48 hours of fasting. Samples were dried and ground to simulate standard industrial processing, then analyzed using real-time PCR and ELISA methods.
Soy showed the clearest evidence of allergen carryover. Soy DNA was detected in all nine treatment samples across the three sampling times, compared with none of the controls. ELISA testing also detected soy protein above the 2.5-parts-per-million (ppm) limit of detection in every treatment sample, including after 48 hours of fasting.
Celery DNA was detected in seven of nine treatment samples and remained detectable after 48 hours of fasting. Detection was significantly more frequent among treated larvae than controls. Almond DNA was detected sporadically at the end of feeding and after 24 hours of fasting, but the difference from controls was not statistically significant. Peanut DNA was not detected in any larval samples.
Gluten concentrations were below the ELISA method's 5-ppm limit of detection in all samples. The researchers cautioned that this result did not necessarily indicate that gluten was completely absent.
Importantly, the researchers found no statistically significant differences in allergen detection among the three sampling times. Therefore, the study did not demonstrate that fasting for up to 48 hours could consistently reduce allergen carryover. The researchers suggested that persistence may depend on the specific allergen and could be influenced by substrate composition, processing conditions, and whether residues remain in the intestinal tract or become associated with larval tissues.
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The authors said the findings have implications for food business operators involved in insect rearing, pointing to allergen-free substrates and appropriate precautionary allergen labeling as potential strategies for protecting consumers. They also stressed that the safety of insect products with respect to feed-derived allergens should be evaluated on a case-by-case basis.
The researchers acknowledged the pilot study's small sample size, with three replicates per sampling point, and called for further research to determine whether detected allergens originate from insects' intestinal contents or tissues.
