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Assessment of aflatoxins B<sub>1</sub>, B<sub>2</sub>, G<sub>1</sub> and G<sub>2</sub> status of home grown maize in Swaziland

Kgomo Hlobsile
GC Bwembya
SS Mamba
JM Thwala


Aflatoxins belong to a group of naturally occurring toxins which contaminate foodstuffs under favourable conditions. Aspergillus flavus and Aspergillus parasiticus produce aflatoxins; the four major aflatoxins which contaminate foodstuffs are B1, B2, G1 and G2. Maize, groundnuts, rice, wheat and other foodstuffs are susceptible to aflatoxin contamination. B1 in the majority of cases is the most abundant, most toxic and the most potent natural carcinogen and is classified as a Group 1 human carcinogen. The extent of contamination varies with geographical location, agricultural practices of farmers and susceptibility of crops to fungal activity during pre- and/ or post-harvesting. Research on groundnuts in Swaziland showed contamination with aflatoxins; however, no data exists on the contamination of maize grains, yet maize is a main staple food of the Swazi nation and its consumption is high. The purpose of the study was to carry out an investigation on the occurrence of aflatoxins on maize grown in various homesteads. Maize samples were collected from different areas in Hhohho, Manzini, Shiselweni and Lubombo regions. Extraction with methanol:water (85:15 v/v) was followed by detection with HPLC-PDA for the analysis of aflatoxins. Results showed that B1 was the most pre-dominant toxin with the lowest concentration at 0.4 ppb and the highest at 25 ppb, both samples were from the Shiselweni region. A total of 90 maize samples were collected for analysis, it was determined that overall contamination with G2 was 20% with 13% above 4 ppb- the European Union (EU) maximum recommended limit. B1 contamination was at 31%, overall, with 18% above 2 ppb- the EU maximum recommended limit. Concentrations for G1 and B2 could not be determined due to poor resolution of peaks. These results show that people in Swaziland are being exposed to aflatoxins through feeding on contaminated maize. There is a growing urgency for the Swaziland government to come up with strategies of teaching the people about food safety.

Keywords: aflatoxins, Aspergillus, maize, contamination, carcinogen, toxin, Swaziland, HPLC-PDA