Aflatoxins, discolouration and insect damage in dried cowpea and pigeon pea in Malawi and the effectiveness of flotation/washing operation in eliminating the aflatoxins

Abstract

Aflatoxin contamination and biodeterioration were examined in 302 samples of dry cowpeas and pigeon peas that were randomly purchased from 9 districts of the Southern Region of Malawi during July and November 2015. Further, the impact of flotation/washing on aflatoxin levels on the pulses was elucidated. Aflatoxin analyses involved immunoaffinity column (IAC) clean-up and HPLC quantification with fluorescence detection (FLD) while legume biodeterioration assessments were done by visual inspection. Aflatoxins were frequently detected in cowpea (24%, max., 66 μg/kg) and pigeon pea (22%, max., 80 μg/kg) samples that were collected in the month of July. Lower aflatoxin incidence of 15% in cowpeas (max., 470 μg/kg) and 14% in pigeon peas (max., 377 μg/kg) was recorded in the November collection. Overall, aflatoxin levels were significantly higher in the pulses that were collected in November. However, there were no significant differences in the total aflatoxin (aflatoxin B (AFB) + AFB + AFG + AFG) levels between the two types of pulses. Remarkably, in 76.2% of the aflatoxin positive cowpea and in 41.7% of the aflatoxin positive pigeon pea samples, aflatoxin G concentration exceeded aflatoxin B Insect damage percentage averaged at 18.1 ± 18.2% (mean ± SD) in the cowpeas and 16.1 ± 19.4% in pigeon peas. Mean discolouration percentage (number of pulses) of the cowpeas and pigeon peas was found to be at 6.7 ± 4.9 and 8.7 ± 6.2%, respectively. Washing and discarding the buoyant fraction was highly efficient in reducing aflatoxin levels; only 5.2 ± 11.1% of the initial aflatoxin level was found in the cleaned samples. In conclusion, cowpeas and pigeon peas sold on the local market in Malawi may constitute a hazard especially if floatation/washing step is skipped.

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

“…Similar to the occurrence pattern or the aflatoxin analogs (AFB1, AFB2, AFG1, and AFG2) previously published for maize, groundnuts, pigeon pea and cowpea from Malawi 2017b), AFB1 was the most frequently detected toxin and occurred in all but one aflatoxin positive sample. AFG1 was the second most frequently detected toxin and was present in 84% of aflatoxin positive samples.…”

“…Generalized global occurrence ratios of the four aflatoxins (AFB 1 + AFB 2 + AFG 1 + AFG 2 ) reported earlier (European Commission EC, 2012;Kensler et al, 2011;Van Egmond and Jonker, 2004) indicate that AFB 1 exceeds half of the sum of the aflatoxins and that AFB 2 and AFG 2 occur in the lowest concentrations. Interestingly, the present unusual aflatoxin profile corroborate published aflatoxin occurrence patterns in maize, cowpea, pigeon pea and groundnut samples from Malawi, with AFG 1 found frequently at equal or higher levels than AFB 1 (Matumba et al, , 2017. This pattern is also apparent in peanut butter samples from neighbouring Zambia (Matumba et al, manuscript in preparation) and in a publication made on samples from neighbouring Mozambique where average AFB 1 and AFG 1 concentrations were comparable (Warth et al, 2012).…”

Farmers knowledge, perceptions and management of Kersting’s groundnut (Macrotyloma geocarpum Harms) insect pests in Benin

“…Heavily infested kersting's groundnut grains are consumed by the interviewed farmers. However, there are reports of a strong relation between insect infestation and aflatoxins contamination in some pulses such as horsegram (Reddy, Brijitha, & Raghavender, 2005), grass pea (Reddy & Nusrath, 1983), cowpea, and pigeon pea (Matumba et al, 2017) which are poisonous and contribute to the genesis of primary liver cancer in Africa (Koshio et al, 2017;Peers, Gilman, & Linsell, 1976). It is therefore urgent to assess the presence of mycotoxins in Kersting's groundnut seeds heavily infested with insects and to raise farmers' awareness on the harmful effects of mycotoxins on human health.…”

The aflatoxin situation in Africa: Systematic literature review

“…Also, flotation of kernels is mentioned as a possible means of separating infected or contaminated kernels from the noninfected /noncontaminated ones. It showed to reduce aflatoxin contamination by as much as 95% (Matumba et al., 2015; Matumba et al., 2017).…”