Editorial: Destruction of Aflatoxins in Contaminated Maize

Abstract

An article in this issue of the journal by Nyandieka et al. describes destruction of aflatoxins in maize using an ammoniation procedure. Aflatoxins are naturally occurring mycotoxins produced by Aspergillus flavus and Aspergillus parasiticus which grow on cereals, oil seeds, spices and nuts. Favourable growth conditions for the mold include high moisture content and high temperature. Contamination can occur at pre-harvest, harvest and post harvest period. They were discovered around 1962 when groundnuts fed to turkeys were found to be contaminated with unknown substance leading to the death of the birds. Over 13 different types of aflatoxins are known, the most common ones being aflatoxins B1, B2, G1, G2, M1 and M2. The most toxic one is aflatoxin B1. Acceptable limit of aflatoxins in cereals for human consumption is about 30 parts per billion (ppb). Aflatoxins are highly oxygenated heterocyclic compounds. They fluoresce strongly in the ultraviolet light (ca 365nm). Aflatoxins B1 and B2 produce blue fluorescence while G1 and G2 produce green fluorescence. After entering the body, aflatoxins are metabolised in the liver to a reactive epoxide intermediate. The liver is the principal organ affected. Aflatoxins are carcinogenic, hepatotoxic, mutagenic and teratogenic. In the dry state, aflatoxins are stable to heat up to the melting point. However in presence of moisture and high temperature there is incomplete but significant destruction of aflatoxins. Hence cooking of contaminated cereals does not decrease the level of toxicity adequately.