Fungal Contamination of Stored Grains and Potential Mycotoxin Risk in Katsina State Markets

Post-harvest fungal contamination of stored grains poses substantial risks to food safety and public health, particularly through mycotoxin production that can cause liver damage and immunosuppression. This study investigated the fungal species associated with maize and groundnut stored in grain markets across Katsina State, in the North West geopolitical zone of Nigeria. A total of 120 grain samples were collected from 10 major markets and processed using direct plating and dilution plating on Sabouraud Dextrose Agar supplemented with chloramphenicol. Fungal colonies were identified by gross morphological features, slide culture, and lactophenol cotton blue staining. Aspergillus flavus was the most frequently isolated species at 42 percent of all isolates, followed by Aspergillus niger, Fusarium species, and Penicillium species. Aflatoxin-producing potential of A. flavus isolates was assessed by UV fluorescence under Wood's lamp. Moisture content analysis revealed that 65 percent of sampled grains exceeded the safe storage threshold of 13 percent moisture content. These findings indicate a high risk of aflatoxin contamination in grain markets across Katsina, with serious implications for consumer health. The study recommends adoption of improved hermetic storage technologies, routine aflatoxin testing, and post-harvest handling training for farmers and grain traders across the North West. Keywords: mycotoxin, Aspergillus flavus, stored grains, Katsina, aflatoxin.