Natural postharvest aflatoxin occurrence in food legumes in the smallholder farming sector of Zimbabwe

Abstract

Aflatoxins, mainly produced by Aspergillus flavus and Aspergillus parasiticus, are highly toxic and may lead to health problems such as liver cancer. Exposure to aflatoxins may result from ingestion of contaminated foods. Levels of AFB, AFB, AFG and AFG in samples of groundnuts (Arachis hypogaea), beans (Phaseolus vulgaris), cowpeas (Vigna unguiculata) and bambara nuts (Vigna subterranean) grown by smallholder farmers in Shamva and Makoni districts, Zimbabwe, were determined at harvesting, using high performance liquid chromatography after immunoaffinity clean-up. Aflatoxins were detected in 12.5% of groundnut samples with concentrations ranging up to 175.9 µg/kg. Aflatoxins were present in 4.3% of the cowpea samples with concentrations ranging from 1.4 to 103.4 µg/kg. Due to alarming levels of aflatoxins detected in legumes versus maximum permissible levels, there is a need to assist smallholder farmers to develop harvest control strategies to reduce contamination of aflatoxins in legumes.

The Burden and Trends of Primary Liver Cancer Caused by Specific Etiologies from 1990 to 2017 at the Global, Regional, National, Age, and Sex Level Results from the Global Burden of Disease Study 2017

“…Aflatoxin B 1 intake is also an important cause of liver cancer. It is primarily produced by Aspergillus flavus and Aspergillus parasiticus and is often present in grains, nuts, and oils harvested in tropical and subtropical regions [18-20]. The risk of liver cancer due to aflatoxin B 1 consumption is higher in India [21, 22].…”

Current Status of Mycotoxin Contamination of Food Commodities in Zimbabwe

“…Zimbabwe should come up with its own standards which cater for the nation’s own diet. For legumes, there are no limits on the level of mycotoxins, making it difficult to enforce law [ 27 ]. There is also a need for researchers to share their findings with the general population.…”

“…Other researchers have worked on groundnuts, beans, cowpeas, and Bambara nuts, where they also isolated Aspergillus and Fusarium [ 21 , 26 , 27 ]; whereas in another study [ 2 ], Aspergillus flavus ( A. flavus ) and Aspergillus parasiticus ( A. parasiticus ) were isolated from peanut butter samples from Zimbabwe and Botswana. This suggests that the temperature of 160 °C used for roasting in commercial peanut butter production [ 28 ] is not high enough to destroy the vegetative cells and spores, not to mention the temperatures used in homemade peanut butter, which are not even monitored [ 2 ].…”

“…Analysis of some food commodities and their products showed the presence of aflatoxins [ 2 , 27 , 28 ]. Foods that have been analysed include maize, groundnuts, peanut butter, beans, Bambara nuts, and cowpeas, among others, as shown in Table 1 .…”

“…All four major aflatoxins were detected in groundnuts, Bambara nuts, beans, and cowpeas in research done by Maringe and others [ 27 ]. Groundnuts and other legumes are important protein supplements in animal feeds [ 57 , 58 , 59 ] as well as the human population [ 48 ].…”