Evaluation of the bright greenish yellow fluorescence test as a screening technique for aflatoxin-contaminated maize in Malawi

The bright greenish yellow fluorescence (BGYF) test has been used with varying success in screening for aflatoxins in maize. This test was applied to 180 maize samples collected from different markets within 12 districts of Malawi in order to evaluate its performance against high performance liquid chromatographic analysis. The number of BGYF grains in 2.5 kg unground samples ranged from 0 to 35 and about 49% of all tested samples had aflatoxin concentrations ranging from 1 to 382 mu g/kg. A total of 65 (36%) of the examined unground samples showed no BGYF. The European Commission recommends a false negative rate of less than 5% for a screening technique to be acceptable. In this study, four BGYF grains per 2.5 kg unground maize sample successfully indicated an aflatoxin contamination of >10 mu g/kg (10 mu g/kg being the maxium tolerable level proposed by the Common Market for Eastern and Southern Africa), with a 4.4% false negative rate. In this case, the amount of confirmatory analyses would be reduced by 63%, if the BGYF test was employed as a screening method. The screening technique therefore offers a practical tool for Malawi and possibly for the Sub-Saharan region

Probabilistic dietary based estimation of the burden of aflatoxin-induced hepatocellular carcinoma among adult Malawians

This research article published by Wageningen Academic Publishers, 2019The risk of aflatoxin-induced hepatocellular carcinoma (HCC) among adults (average body weight of 60 kg) in Malawi was assessed based on aflatoxin B1 (AFB1) exposure through groundnut and maize consumption, by Monte Carlo simulation. The risk (cases per year per 100,000 people) of aflatoxin-induced HCC was estimated based on the AFB1 exposures estimated by this study and hepatitis B virus infection prevalence published for Malawi. AFB1 exposures were estimated by probabilistically combining data of AFB1 contamination in 338 groundnut and 604 maize samples with data of per capita groundnut and maize consumption in 274 households. Aflatoxins in the samples were analysed using validated LC-MS/MS, HPLC and VICAM based methods. The groundnut and maize consumption survey was based on household expenditure technique. The simulated mean AFB1 exposures through consumption of groundnuts, maize, and combination thereof were 28±65, 42±174, and 71±211 ng/kg. body weight (bw)/day, respectively. The estimated HCC risks were 1.26±2.72, 1.86±6.66 and 3.10±6.85 cases per 100,000 persons per year, respectively. Further, hypothetical eradication of hepatitis B virus (HBV) reduced the risk of HCC by 78%. This reaffirms the need for integrating HBV vaccination in the fight of aflatoxin induced HCC

Participatory evaluation of groundnut planting methods for pre-harvest aflatoxin management in Eastern Province of Zambia

Aflatoxin contamination remains a major challenge for smallholder groundnut producers in Southern Africa. This is compounded by the stringent aflatoxin regulatory regimes in the lucrative international markets that continue to deny groundnuts produced in this region the access to markets. Participatory on-farm experiments were carried in 2016 and 2017 in Chinkhombe (Katete) and Kalichero (Chipata), and on-station trials at Mount Makulu Central Research Station (Chilanga) to evaluate the efficacy of groundnut planting methods: planting in double rows, single rows, tied ridges and on flatbeds, for pre-harvest aflatoxin management. Planting on flatbeds (no ridges), a popular planting method in most parts of Zambia was designated as the baseline. Significantly low (p < 0.05) levels of aflatoxin, (10.3 ± 3.1 mg/kg) were recorded in the groundnuts planted on tied ridges, and less than 22% of these had aflatoxin levels above the Zambia regulatory limit of 10 mg/kg, compared to more than 40% in other methods. Except for double rows, significantly higher pod yield, 1193 kg/ha, was recorded in groundnuts planted on tied ridges compared to other pre-harvest management options. A reduction of 37 and 81% in aflatoxin contamination was observed in groundnuts planted on single rows and tied ridges, respectively compared to an increase of 39.2% in double rows above 54.3 ± 10.9 mg/kg recorded in flatbeds. In addition, tied ridging was observed to improve plant vigour, lower disease incidence, insect pest and weed infestation. It is clear that the evaluation of these practices on-farm enabled more farmers to be more aware of the effects of these methods and get motivated to adopt them. It is thus imperative that participatory on-farm evaluations of existing aflatoxin management options are carried out as they are an essential step in influencing adoption and uptake of preharvest management control methods among smallholder farmers

Managing aflatoxin in smallholder groundnut production in Southern Africa: Paired comparison of the windrow and Mandela cock techniques

Timely drying of groundnuts is important after harvest. In most parts of sub-Saharan Africa, moisture content reduction is practically achieved by solar drying. In particular, the groundnuts are traditionally cured in the field using the inverted windrow drying technique. Recently, the Mandela cock technique, a ventilated stack of groundnut plants with a chimney at the center, has been introduced in the southern Africa region with the aim of reducing moisture content and the risk of aflatoxin contamination. An on-farm study was conducted in Malawi to compare the effectiveness of the Mandela cock and Windrow drying techniques with respect to aflatoxin control. For two consecutive years, farmers (2016, n = 29; 2017; n = 26) were recruited to test each of the two drying techniques. A mixed-design ANOVA showed that the Mandela cock groundnut drying technique led to sig- nificantly (p < 0.001) higher aflatoxin levels in groundnut seed compared to the traditional inverted windrow drying (5.7 μg/kg, geometric mean vs 2.5 μg/kg in 2016 and 37.6 μg/kg vs 8.4 μg/kg in 2017). The present findings clearly demonstrate the need for regulation and technology validation if farmers and consumers are to benefit

Aflatoxin B1 levels in groundnut products from local markets in Zambia

In Zambia, groundnut products (milled groundnut powder, groundnut kernels) are mostly sold in under-regulated markets. Coupled with the lack of quality enforcement in such markets, consumers may be at risk to aflatoxin exposure. However, the level of aflatoxin contamination in these products is not known. Compared to groundnut kernels, milled groundnut powder obscures visual indicators of aflatoxin contamination in groundnuts such as moldiness, discoloration, insect damage or kernel damage. A survey was therefore conducted from 2012 to 2014, to estimate and compare aflatoxin levels in these products (n = 202), purchased from markets in important groundnut growing districts and in urban areas. Samples of whole groundnut kernels (n = 163) and milled groundnut powder (n = 39) were analysed for aflatoxin B1 (AFB1) by competitive enzyme-linked immunosorbent assay (cELISA). Results showed substantial AFB1 contamination levels in both types of groundnut products with maximum AFB1 levels of 11,100 μg/kg (groundnut kernels) and 3000 μg/kg (milled groundnut powder). However, paired t test analysis showed that AFB1 contamination levels in milled groundnut powder were not always significantly higher (P > 0.05) than those in groundnut kernels. Even for products from the same vendor, AFB1 levels were not consistently higher in milled groundnut powder than in whole groundnut kernels. This suggests that vendors do not systematically sort out whole groundnut kernels of visually poor quality for milling. However, the overall contamination levels of groundnut products with AFB1 were found to be alarmingly high in all years and locations. Therefore, solutions are needed to reduce aflatoxin levels in such under-regulated markets

Keeping mycotoxins away from the food : does the existence of regulations have any impact in Africa?

Following the discovery of aflatoxins in the early 1960s, there have been many studies leading to the uncovering of many mycotoxins and the understanding of associated health effects in animals and humans. Consequently, there has been a global increase in the number of countries with mycotoxin regulations in foods. However, many African countries have only regulations for aflatoxins (or a few other mycotoxins) in specific foods, or no regulations at all. This paper critically reviews the challenges thwarting the establishment of mycotoxin regulations and their impacts on human dietary mycotoxin exposure in Africa. Mycotoxin regulatory limits for different countries are compared with mycotoxin tolerable daily intakes established by international food safety bodies taking into account consumption patterns. The agrarian setup, food insecurity, and mycotoxin analytical challenges in African countries are discussed; and more feasible mycotoxin dietary exposure reduction strategies are proposed

Effectiveness of hand sorting, flotation/washing, dehulling and combinations thereof on the decontamination of mycotoxin-contaminated white maize

Maize is one of the major staple foods of Sub-Saharan Africa and is consumed as whole or dehulled grain. In this region, where the environmental conditions favour fungal growth and mycotoxin production, the majority of the population are subsistence consumers who, unfortunately, have little or no access to mycotoxin testing of their food. In an attempt to develop feasible reduction strategies in dietary mycotoxin exposure of the population, a three-factorial design experiment was conducted to examine and compare the efficacy of hand sorting, flotation, dehulling and combinations thereof in removing naturally occurring aflatoxins, fumonisins, nivalenol, deoxynivalenol and alternariol in shelled white maize. Regression analysis was used to determine the significant (p<0.05) process variables on the removal of mycotoxins from the maize. Results from this experiment indicated that hand sorting had the greatest effect on mycotoxin removal, while flotation yielded the least effect. In particular hand sorting left <6% of aflatoxin B1 and <5% of fumonisin B1. Based on these results, hand sorting of maize grains is being recommended as a last line of defence against mycotoxin exposure among subsistence consumers

Evaluation of Metal(loids) Concentrations in Soils of Selected Rice Paddy Fields in Malawi

The aim of this study was to obtain baseline data for heavy metal(loids) concentrations of rice paddy fields to evaluate the impacts of soil metal(loids) concentrations on quality of rice, and to identify sources of metal(loids) pollution of paddy fields in Malawi. In total, 66 soil samples were collected from 22 different smallholder rice farmers&rsquo; paddy fields (sites) in Malawi. Concentrations of metal(loids) (arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), manganese (Mn), lead (Pb), uranium (U), and gallium (Ga)) were measured using inductively coupled plasma mass spectrometry (ICP-MS) after acid block digestion with a mixture of concentrated nitric acid (70% HNO3) and hydrogen peroxide (30% H2O2). Measured soil metal(loids) concentrations were compared with Soil UK CLEA soil metal(loids) guidelines, maximum allowable limits (MAL) recommended by the World Health Organization (WHO), the Chinese Environmental Quality Standards (CEQS) for soil metal(loids) concentrations in agricultural soils, and the normally reported soil metal(loids) concentrations in agricultural fields worldwide. Results indicated that mean soil As (2.2 mg As kg&minus;1), Cd (0.044 mg Cd kg&minus;1), Pb (11 mg Pb kg&minus;1), Co (14 &plusmn; 6 mg Co kg&minus;1), Mn (601 mg Mn kg&minus;1), U (2.02 mg U kg&minus;1), and Ga (24 mg Ga kg&minus;1) concentrations were at least three times lower than the respective guidelines and MAL recommended by WHO, UK CLEA, and CEQS (20 mg As kg&minus;1, 0.3 mg Cd kg&minus;1, 32 mg Pb kg&minus;1, 50 mg Co kg&minus;1, and 2000 mg Mn kg&minus;1). The values obtained in this study were also within the normally reported metal(loid) concentrations for unpolluted agricultural soils worldwide. However, the mean Cr concentration (78.0 mg Cr kg&minus;1) obtained in this study was higher than that reported for agricultural soils in China (27 &plusmn; 5 mg Cr kg&minus;1; range: 22&ndash;39 mg Cr kg&minus;1) but was within the normally reported Cr concentrations (1&ndash;100 mg Cr kg&minus;1) for unpolluted soils. These findings suggest that metal(loids) concentrations of Malawian rice paddies pose no threat to production to elevated metal(loids) accumulation in rice, and that rice paddies should be safeguarded from contamination. However, further research is required to investigate the impacts of factors such as source of irrigation of water, water management regimes, soil cation exchange capacity, organic manure/composts amendments, and the application of inorganic fertilizers on uptake, transfer, and translocation of soil metal(loids) to various parts of rice plants, even when the soil metal(loids) concentrations are low

Reduction of aflatoxins during brewing of a Malawian maize‐based non‐alcoholic beverage, thobwa

Abstract This study reports onthe effect of various production steps on levels of aflatoxins during preparation of thobwa, a traditional maize‐based fermented non‐alcoholic beverage, brewed across Malawi. The effect of boiling, fermentation and their interaction on the level of aflatoxins, the trends of aflatoxin reduction during brewing, and the distribution of aflatoxins between the solid and liquid phases of the beverage were studied using VICAM AflaTest immunoaffinity fluorometric assay. Fermenting and boiling thobwa pre‐mix‐, with initial aflatoxin content of 45–183 μg/kg, resulted in aflatoxin reduction of 47% (13–61 μg/kg) on average. Fermentation and boiling contributed about 20 and 33% aflatoxin reduction, respectively, but without interactive effect between the two factors. Fermenting the thobwa for 24 h led to further reduction of aflatoxins to about 37% of the initial content, and remainedconstant for up to 8 days. Thobwa is a popular beverage in Malawi which is consumed in large quantities by all gender categories including infants, therefore the presence of aflatoxins may constitute a significant health risk factor. This study highlights the need to use raw materials with low levels of aflatoxins for production of maize‐based non‐alcoholic beverages to ensure consumer safety