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.
Highlights
In semi-arid agro-ecologies of central Tanzania, most farmers practice inter-cropping or mixed cropping systems that involve diverse drought-tolerant crops such as bambara nut (Vigna subterranea (L.) Verdc.), sorghum (Sorghum bicolor (L.) Moench), sunflower (Helianthus annus L.), maize (Zea mays, L.), cowpea (Vigna unguiculata (L.) Walp), pigeonpea
The frequency of aflatoxigenic Aspergillus species in soil was not associated with aflatoxin B1 (AFB1) contamination in crop products, in groundnut (Table 2)
Predisposition of crops to AFB1 contamination was influenced by time of planting, crop variety, postharvest handling, and storage conditions (Diao et al 2015)
Summary
In semi-arid agro-ecologies of central Tanzania, most farmers practice inter-cropping or mixed cropping systems that involve diverse drought-tolerant crops such as bambara nut (Vigna subterranea (L.) Verdc.), sorghum (Sorghum bicolor (L.) Moench), sunflower (Helianthus annus L.), maize (Zea mays, L.), cowpea (Vigna unguiculata (L.) Walp), pigeonpea These crops are susceptible to infection by Aspergillus spp., which are fungi that produce a group of toxins known as aflatoxins (Guchi 2015). Mycotoxin Res (2017) 33:323–331 climate common to the tropical semi-arid agro-ecologies of sub-Saharan Africa are conducive to infection of crop produce by Aspergillus spp. and subsequent contamination with aflatoxins (Bosch et al 2004; Yu and Yuan 2004). Chronic exposure to low or moderate amounts of AFB1 through consumption of contaminated food products can cause liver cancer (Wild 2007), immune suppression (Jolly et al 2013), and stunted growth in children, as reported previously (Gong et al 2003; Williams et al 2004). The economies of many sub-Saharan African countries, being largely agrarian, with limited management of AFB1 contamination, miss the opportunity to engage in competitive markets (Monyo et al 2012)
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