Enzyme immunoassays for the detection of mycotoxins in plant-based milk alternatives: pitfalls and limitations.

Plant-based milk alternatives (PBMAs) are a potential source of mycotoxin uptake. To ensure food safety, simple and rapid testing methods of PBMAs for mycotoxins are therefore required. This study investigated the applicability of enzyme immunoassay (EIA) methods for direct testing of PBMAs without sample extraction. Mycotoxin analyses included aflatoxin B1 (AFB1), sterigmatocystin (STC), ochratoxin A (OTA), deoxynivalenol (DON), and T-2/HT-2-toxin (T-2/HT-2). It was found that the PBMA matrix negatively affected the EIA to varying degrees, thus affecting the reliability of the results. A dilution of PBMAs of at least 1:8 was necessary to overcome matrix interference. This resulted in calculated detection limits of 0.4 µg/L (AFB1), 2 µg/L (STC), 0.08 µg/L (OTA), 16 µg/L (DON), and 0.4 µg/L (T-2/HT-2). After analysis of 54 PBMA products from German retail stores, positive results in at least one test system were obtained for 23 samples. However, most positive results were near the calculated detection limit. Control analyses of selected samples by LC-MS/MS for AFB1, STC, and OTA qualitatively confirmed the presence of trace amounts of STC in some samples, but quantitative agreement was poor. It was concluded that the high diversity of ingredients used in PBMAs led to a highly variable degree of sample matrix interference even in a 1:8 dilution. Since the use of higher dilutions conflicts with the need to achieve low detection limits, the application of EIA for routine mycotoxin analysis in PBMA for mycotoxins requires further study on the development of a feasible sample preparation method.

Metabolic fate and toxicity reduction of aflatoxin B1 after uptake by edible Tenebrio molitor larvae.

The use of insects as food and feed is gaining more attention for ecological and ethical reasons. Despite the high tolerance of edible yellow mealworm (Tenebrio molitor) larvae to aflatoxin B1 (AFB1), the metabolic fate of the toxin along with its toxic potential in the insect is uncertain. The present study aimed at investigating the AFB1 mass balance and the metabolite formation in a feeding trial with AFB1-contaminated grain flour. T. molitor larvae tolerated the AFB1 level of 10,700 µg/kg in the feed, however, weight gain was decreased by 15% over a 4-weeks feeding period. The investigation of the phase I metabolite pattern revealed the formation of AFM1 and a novel presumably monohydroxylated compound in larvae extracts that was not formed by reference incubation with rat, bovine or porcine liver microsomes. Mass balance quantification of ingested AFB1 revealed that 87% of the initial toxin remain undetected in larval body or residue. Analysis of histone H2Ax phosphorylation in human liver cells as a surrogate for genotoxicity showed that extracts from exposed larvae did not exhibit an elevated toxic potential. Although toxicological uncertainties remain due to the undetected transformation products, the resulting mutagenicity of the edible larvae appears to be low.