Invisible Threats: Characterization of Aflatoxigenic Fungi in Post-Harvest Cashew and Groundnut in Ogun State, Nigeria.

Implications for Food Safety and public health

Abstract

The global reliance on nuts as a dietary staple underscores the critical need for robust food safety measures, particularly concerning post-harvest contamination. This investigation sought to characterize the fungal microbiome of stored cashew nuts and groundnuts sourced from Alabata, Ogun State, and to assess the prevalence of aflatoxin-producing species. Using a combination of conventional mycological plating and species identification, along with a specialized Neutral Red Desiccated Coconut Agar for rapid screening, fungal contamination was quantified. Aflatoxin levels were further confirmed and measured using High-Performance Liquid Chromatography (HPLC), providing a precise assessment of mycotoxin load. The analysis revealed significant fungal populations in both nut types, with cashew nuts exhibiting total counts ranging from 4.0×103 to 2.4×104 colony-forming units per gram (cfu/g). Five distinct fungal species were isolated from cashew nuts, of which Aspergillus niger, A. flavus, and A. fumigatus were the most prevalent. Critical findings demonstrated that while A. flavus and A. fumigatus isolates showed a high potential for aflatoxin production, the A. niger strains identified in this study were non-aflatoxigenic. HPLC analysis showed total aflatoxins in groundnut and cashew samples ranging from 0.05 to 12.41 µg/kg, with low but consistent AFB1 levels. Most samples were within the EU limit of 4 µg/kg, though a few exceeded it, indicating persistent contamination and potential public health risks The confirmed presence of these potent mycotoxin producers in a widely consumed food source highlights a tangible public health risk, given their established link to severe health conditions, including primary hepatocellular carcinoma. This research underscores the necessity for implementing rigorous hygiene protocols and enhanced storage practices to safeguard against fungal proliferation and subsequent mycotoxin exposure in these staple crops.