Aflatoxins contamination in processed cassava in Malawi and Zambia

Abstract

Strains of the Aspergillus fungi, especially A. flavus and A. parasiticus, primarily produce aflatoxins which are a major health concern to man and livestock because of their acute and chronic health effects. Aflatoxins pose the greatest risk to health in tropical Africa because of their widespread prevalence and high toxicity; carcinogenic (cause liver and esophageal cancer) effect, immune system suppressing and anti-nutritional  contaminants in many food commodities and even cause death. Aflatoxins have also been reported to compromise vaccine efficacy in experimental animals. Due to the seriousness of aflatoxins, international agencies have restricted levels of aflatoxins to 20 ppb in food materials as the maximum permissible level in the United States and 4 ppb total aflatoxins and under 2 ppb aflatoxin B1 in Europe. These regulations directed at minimizing human exposure to aflatoxins results in severe economic loss to producers, processors and marketers of the contaminated crop. A study was conducted in Malawi and Zambia to assess the level of fungal and mycotoxins’ contamination in commonly processed cassava products. A total of 92 and 88 samples of processed cassava products comprising makaka, flour, kanyakaska, kadonoska, scrapes and grates were collected in the rainy season of 2008 and 2009 in Malawi, respectively. Further, 22 samples of processed cassava products comprising dried cassava chips and flour were collected in the rainy season of 2009 in Zambia. The samples were analyzed for fungal and aflatoxins B1, B2, G1 and G2 contamination using the Romer mini-column method and the VICAM AflaTest  immunoaffinity fluorometric method. None of the samples in 2008 were contaminated with aflatoxins. Similar results were obtained in 2009 with almost all the samples in Malawi and Zambia having aflatoxin levels much lower (<2.0 ìg/kg in Malawi and <4.2 ìg/kg in Zambia) than the Codex Alimentarius Commission (CAC) maximum permissible level of aflatoxins of 10.0 ìg/kg, implying that the cassava products analyzed were safe for human consumption. However, further studies are needed to cover a larger sample size over a period of a year to represent all seasons in the cassava producing and consuming areas and conclusively make certain the safety of these products for human consumption.

Key words: Cassava, consumption, aflatoxin, food, safety