Mycotoxin migration in Alternaria alternata molded tomatoes: an on-going challenge for food safety and food waste management

Alternaria species are common mycotoxigenic fungi contaminating tomatoes which can lead to tomato-based products being contaminated by one or more mycotoxins. At the consumer level, there is a lack of information on the impact of storage conditions on Alternaria growth on tomatoes but also mycotoxin production and migration, yet this food safety hazard needs to be considered. In this context, we artificially inoculated tomatoes with a multi-mycotoxin producing A. alternata UBOCC-A-124001 isolate and incubated tomatoes in conditions mimicking refrigerated (8°C) or room temperature (20°C) storage until fungal lesions reached 1, 2 and 3 cm. Five mycotoxins were produced once lesions reached 2 cm in diameter. Highest concentrations were reached for 2 or 3 cm lesions at 20°C, namely 168758 ng/g for tenuazonic acid (3 cm) followed by 1146+/-1844 ng/g for alternariol (2 cm), 410 ng/g for altertoxin-I (3 cm), 89+/- 95 ng/g for alternariol methyl ether (2 cm) and 4.4 ng/g for altenuene (2 cm) while these mycotoxins were detected at much lower concentrations or <LOD at 8°C. Mycotoxins migrated once lesion sizes reached 2 and 3 cm diameters, but highest contents still remained close to fungal lesions. We hypothesize that some of the produced mycotoxins remain near the fungus or in specific tissues while others, as tenuazonic acid, diffuse well beyond the lesion. Overall, a strong reduction in mycotoxin content was observed at a 3 cm distance, even for the largest lesions. For small lesions, mycotoxin migration was limited. We therefore recommend removing a 2 cm portion around and below the fungal lesion for lesions up to 2 cm in diameter to limit mycotoxin exposure. For 3 cm lesions or greater, migration into the entire tomato occurred thus tomatoes should be discarded to ensure sufficiently protective conditions for consumer food safety. We recommend to consumers to store tomatoes in cool conditions to limit fungal growth and reduce mycotoxin production, thus contributing to better food waste management practices. • Up to five mycotoxins were produced and migrated in A. alternata molded tomatoes stored under consumer conditions • Tenuazonic acid was produced at highest concentrations and migrated farthest • Alternariol, alternariol monomethyl ether, altenuene and altertoxine-I contents were mostly concentrated near A. alternata growth • Mycotoxin migration was most intense for 2 and 3cm fungal lesions • Sufficiently protective recommendations are needed to ensure consumer safety as mycotoxin co-occurrence was observed • Cold storage limits mold growth and mycotoxin migration • Food waste due to moldy tomatoes can be reduced for smaller sized mold lesions