The Critical Factor in Grain Storage Mycotoxin Risk: Beyond Field Contamination

This analysis is based on the book chapter "Relevant fungal species and associated mycotoxins in storage," authored by Carla Cervini, Andrea Patriarca, Carol Verheecke-Vaessen, and Angel Medina, published in Mycotoxins, DOI: 10.1163/9789004724969_011.

While pre-harvest contamination receives significant attention, storage is identified as the most critical stage in the food supply chain where fungal growth and mycotoxin accumulation can severely impact food and feed safety. Inadequate ventilation, improper temperature and humidity control, and poor sanitation practices can turn storage facilities into ecosystems that encourage the development of mycotoxigenic fungi such as Aspergillus spp., Fusarium spp., and Penicillium spp. This research underscores that targeted environmental management during storage is the most effective preventative measure.

For Producers and Professionals, the immediate focus must be on water activity (aW) and temperature. The study highlights that for wheat, Penicillium verrucosum is the exclusive source of the critical storage mycotoxin, Ochratoxin A (OTA), and its growth significantly increases if the amount of water available for fungal growth increases at any point. Preventing OTA accumulation is achieved by timely harvesting, immediate drying of crops, and ensuring adequate drying capacity. The design of grain storage facilities and their cleanliness are equally crucial, requiring prompt addressing of issues like condensation and poor ventilation to maintain the "Safe Zone" where no fungal growth or toxin production occurs. For maize, a recommended safe storage condition is a maximum of 14.5–15% moisture content (equivalent to 0.70 aW) to prevent the accumulation of highly toxic aflatoxins, which are primarily produced by Aspergillus flavus during the storage phase.

For Academics and Key Opinion Leaders (KOLs), a central point of debate is the influence of storage conditions on the relative abundance of conjugated mycotoxins. Studies show that specific storage conditions (water activity and temperature) not only influence the production of free mycotoxins but also significantly impact the ratio of free versus conjugated forms, such as DON-3-glucoside and ZEN-14-sulfate compared to their parent toxins (DON and ZEN). Given that these conjugated mycotoxins can revert to their parent forms in biological systems, their prevalence has significant implications for toxicological assessment and food safety risk management. Furthermore, the global challenge is exacerbated by disparities in infrastructure, with developing countries often experiencing higher contamination levels, a problem potentially worsened by the influence of climate change on temperature and humidity fluctuations.