Fungal biodiversity and mycotoxin risk in cheese aged in natural environments

Cheese, a dairy product rich in proteins, fats, and vitamins, is prone to microbial growth, which is crucial for its flavor and texture development, especially during ripening. The microbiota includes fungi as secondary starters, leading flavor, aroma, texture, color, appearance, yield, and nutritional composition in the ripening step of cheese production. Filamentous fungi are a particular reason for concern due to their ability to produce mycotoxins, which can compromise the safety of the cheese, especially in artisanal cheeses, where uncontrolled “addition” of fungal strains increases the risk of mycotoxin production, making risks not fully assessed. Based on current literature, cheese is particularly susceptible to contamination by mycotoxins and related fungal species belonging to the Aspergillus and Penicillium genera. However, the European Commission currently only regulates aflatoxin M1 levels in milk and dairy products, with no specific limits for other mycotoxins produced by filamentous fungi in cheese. Studies have already highlighted since 2007 the risk of ochratoxin A (OTA) in cheese, especially from species known to produce it [1]. In 2020, the European Food Safety Authority conducted a risk assessment on OTA contamination in food, including dairy products, and emphasized the need for further data collection on OTA levels to refine risk assessments and enhance food safety measures. The present study, built upon these recommendations, investigates fungal communities in semi-hard cheese ripened under different environmental conditions and assesses associated mycotoxin risks. Cheese maturation was monitored in parallel in natural cave environments and controlled aging refrigerated cells, over different ripening periods, to evaluate OTA risks. Washing and brushing protocols were applied to assess their impact on mycotoxigenic fungal occurrence and potential toxin production. Monitoring activities revealed the presence of Aspergillus westerdijkiae, a known OTA producer, predominantly in cave-ripened cheeses. Chemical analyses, performed both in vitro and on cheese samples, confirmed the toxigenic potential of these fungal strains and detected OTA occurrence (12÷47 μg/kg). These findings highlight the need for a balanced approach that preserves the fungal biodiversity contributing to the uniqueness of traditional cheese aging, while limiting potential mycotoxin risks. This research contributes to the targeted monitoring of cheese to assess authenticity and ensure consumer safety.