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

Abstract

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 ng/g for alternariol (2 cm), 410 ng/g for altertoxin-I (3 cm), 89 ng/g for alternariol monomethyl 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, with highest contents 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