Not too dry, not too wet

Various media reports on high levels of aflatoxins in various foodstuffs have again fuelled the ongoing attention to these compounds which are known for causing cancer. They are produced by certain moulds, notably Aspergillus flavus, a fungus found in the soil. It thrives under hot, humid conditions and as a general rule attacks crops under drought stress such as groundnuts, maize, sorghum and chili peppers. It is also found in stored grains and even processed products like peanut butter or vegetable oils. Since aflatoxins do not smell or have any taste, they are difficult to detect and are extremely harmful to poultry, humans, and to a lesser extent livestock. In April 2001, high levels of aflatoxins were found in the peanut butter which a South African nutrition programme provided to schoolchildren. A recent study by Ragaa El Hadi Omer in Sudan has shown that poorly stored groundnuts in the country contain twenty times more aflatoxins than the levels permitted by the World Health Organisation (WHO). For those people who do not manufacture a certain enzyme in Sudan, half the population or who have had hepatitis, the aflatoxins are even more than fifteen times more likely to lead to liver cancer. The problem is aggravated by the fact that most farmers process lower quality groundnuts into groundnut butter for home consumption. In the early 1990s, as part of the trade bans which led to the collapse of much groundnut production in West Africa, many countries in Europe and elsewhere imposed strict permissible limits of aflatoxin levels. These ranged from zero detectable aflatoxin to around a standard of 10 parts per billion (micrograms per kilogram) for human consumption, of which 5 parts per billion may be the most dangerous type: aflatoxin B1. Various methods exist to detect the toxin in foods, but these are too expensive for smallholder farmers. Prevention measures offer a better solution, such as preventing drought stress in maize and sorghum, and considering irrigation during pollination. Preventing drought stress in pre-harvest groundnuts will prevent cracks in the shells which allow Aspergillus to enter. On the other hand, prevention of humid conditions in stored grains and groundnuts and avoidance of feeding bad quality grains and groundnuts to animals, especially poultry, is also recommended. [caption to illustration] Aspergillus flavus (magnified here 1,000 times) poses great health risks Mycotoxins in grain CTA, GASGA, 1997. 12 pp. CTA number 812. 5 credit points

Mycotoxins in grain CTA, GASGA, 1997. 12 pp. CTA number 812. 5 credit points