Aflatoxin prevalence and association with maize grain physical and nutritional qualities in the informal markets in Meru County, Kenya

In Kenya, aflatoxin contamination in maize remains a persistent issue, with potential negative impacts on both public health and economic growth. Aflatoxins are toxic secondary metabolites produced by certain mold species, primarily Aspergillus flavus. The extent of Aspergillus fungal invasion in maize grains and the resulting increase in aflatoxin levels is heavily influenced by pre-and post-harvest practices. Before harvest, factors such as insect damage and exposure to warm, humid conditions increase the crop's susceptibility to Aspergillus infection and subsequent aflatoxin formation. Post-harvest, additional risks arise when kernels are damaged by pests like rats or when they are stored in unfavorable conditions for extended periods, leading to significant aflatoxin accumulation. This study examined the prevalence of aflatoxin contamination in maize and its association with the physical and nutritional characteristics of grains collected from 49 informal markets across eight sub-Counties in Meru County, Kenya. A total of 353 maize samples were collected from traders. A competitive enzyme-linked immunosorbent assay (ELISA) was used to determine aflatoxin levels, while proximate analyses of ground maize grain samples were conducted in duplicate, following the guidelines of the Association of Official Analytical Chemists (AOAC). The physical characteristics of maize grains including the proportions of undamaged, broken, and insect-damaged grains along with moisture content, were also assessed. The average aflatoxin level in maize samples was 8.66 ppb, with 35.2% containing less than one ppb (low or none), 47.8% falling between 1–10 ppb (moderate), and 17.0% exceeding 10 ppb (high). Physical factors found to be positively correlated with aflatoxin contamination included high proportion of broken grains, insect damage, and elevated moisture content. However, nutritional parameters, including fat, starch, and protein content, were consistent across sub-Counties and did not significantly associate with aflatoxin levels. To mitigate aflatoxin contamination, the study recommends implementing management practices such as ensuring adequate drying of maize to a moisture content below 13%, proper storage and transportation, and optimizing threshing and harvesting times to improve kernel quality. Relevant government agencies should support farmers, traders, and consumers by disseminating information and providing training programs on these practices. Key words: Aspergillus flavus, Aflatoxin levels, Food handling practices, mitigate, Maize