Occurrence of aflatoxins and its management in diverse cropping systems of central Tanzania

Abstract

The staple crops, maize, sorghum, bambara nut, groundnut, and sunflower common in semi-arid agro-pastoral farming systems of central Tanzania are prone to aflatoxin contamination. Consumption of such crop produce, contaminated with high levels of aflatoxin B1 (AFB1), affects growth and health. In this paper, aflatoxin contamination in freshly harvested and stored crop produce from central Tanzania was examined, including the efficacy of aflatoxin mitigation technologies on grain/kernal quality. A total of 312 farmers were recruited, trained on aflatoxin mitigation technologies, and allowed to deploy the technologies for 2 years. After 2 years, 188 of the 312 farmers were tracked to determine whether they had adopted and complied with the mitigation practices. Aflatoxigenic Aspergillus flavus and aflatoxin B1 contamination in freshly harvested and stored grains/kernels were assessed. A. flavus frequency and aflatoxin production by fungi were assayed by examining culture characteristics and thin-layer chromatography respectively. AFB1 was assayed by enzyme-linked immunosorbent assay. The average aflatoxin contamination in freshly harvested samples was 18.8 μg/kg, which is above the acceptable standard of 10 μg/kg. Contamination increased during storage to an average of 57.2 μg/kg, indicating a high exposure risk. Grains and oilseeds from maize, sorghum, and sunflower produced in aboveground reproductive structures had relatively low aflatoxin contamination compared to those produced in geocarpic structures of groundnut and bambara nut. Farmers who adopted recommended post-harvest management practices had considerably lower aflatoxin contamination in their stored kernels/grains. Furthermore, the effects of these factors were quantified by multivariate statistical analyses. Training and behavioral changes by farmers in their post-harvest practice minimize aflatoxin contamination and improve food safety. Moreover, if non-trained farmers receive mitigation training, aflatoxin concentration is predicted to decrease by 28.9 μg/kg on average.

Aflatoxins: Production, Structure, Health Issues and Incidence in Southeast Asian and Sub-Saharan African Countries

“…Moreover, Villers [105] quoted that aflatoxin concentration increased by 200 times in peanut after 2 months of storage under conventional conditions in Mali and by 300 times in maize after 3 months of storage in traditional facilities in Uganda. Such results were corroborated on bambara nut (Vigna subterranean, L), groundnut, maize, sunflower, and sorghum from different AEZs in Tanzania [99]. Strikingly high aflatoxin levels were recorded in commercial peanut samples collected from different marketing structures in Kenya, with the highest levels, e.g., 32,328 g/kg, being recorded in informal market outlets and poorly designed stores of retailers and stockists [110], see also Tables 7 and 8.…”

“…In fact, there is a multiplicity of factors that interfere with the effect of the climate type at different production stages from plant development to crop storage [18,62]. It is increasingly recognized that management systems with rigorous implementation of the good agricultural practices (GAPs) and farmer trainings are critical measures to mitigate the incidence of aflatoxins in agricultural products regardless of the climate type [18,67,80,[97][98][99]. The implementation of such measures in South Africa in the framework of a project on the "Adaptation of agricultural practices to climate change in Sub-Saharan Africa (CAADP)" aimed at "good agricultural adaptation practices" [100], appears to have been successful in controlling aflatoxin contamination.…”

Present Status and Perspective on the Future Use of Aflatoxin Biocontrol Products

“…Examples of exceptions include cases when the contamination levels reach a national health emergency, such as maize destruction in areas of Kenya, and the banning of several brands of maize flour and peanut butter in Kenya, Rwanda, and Uganda [16][17][18][19]. Therefore, in emerging and developing nations, most contaminated crops enter the food and feed chains, regardless of their aflatoxin content [3,[20][21][22][23][24][25]. The absence of mechanisms to enforce aflatoxin tolerance levels results in chronic aflatoxin exposure with subsequent lack of access to markets, poverty, low well-being, poor economic growth, being among other constraints in the affected populations [2,26,27].…”

“…The notion that aflatoxin contamination is a problem restricted to post-harvest stages still incorrectly permeates in certain regions and sectors across the globe. Aflatoxin contamination usually starts in the field and, if post-harvest handling is deficient, aflatoxin concentrations can dramatically increase during storage [22,24,26,29,30]. Several cultural practices and technologies that prevent or limit the contamination process in the field are available for both highly mechanized and small-scale agricultural systems.…”

“…Chemical detoxification is mostly limited to human food, but some compounds (e.g., ammonium, hydrated bentonite, magnetic carbon) can reduce aflatoxin concentration in the final product [36]. Finally, other practices such as crop drying, improved sanitation, controlled processing and storage conditions, significantly contribute to reduce aflatoxin accumulation [22,24,26,30,[37][38][39][40].…”