Effect of heat, acid treatment and dehulling on aflatoxins in maize and maize products

Abstract

The effect of heat on aflatoxins B1 and B2 during the cooking of two naturally contaminated fermented Ghanaian foods, Koko and Banku was studied. Boiling Koko for 25 minutes reduced aflatoxin B1 and B2 levels by 74% and 57% respectively. The greatest reduction of 45% and 43% for aflatoxins B1 and B2 occurred after boiling for 5 minutes. Cooking Banku (a semi-solid product of reduced moisture content) for 25 minutes did not have any effect on aflatoxins B1 and B2 levels, implying the important role played by moisture in aflatoxin destruction. The addition of citric and phosphoric acids to the fermented maize slurries before cooking into Koko resulted in significant reductions in aflatoxin B1 levels with the degree of reduction increasing with decreasing pH in the range pH 3.5 to 1.3. Subsequent cooking of the slurry resulted in further reductions in aflatcxin B1 and B2 levels. Dehulling of maize kernels as done durlnq the preparation of Abolo (a slightly fermented and steamed maize product) appeared to qive a pronounced reduction in aflatoxin content which could be up to 86% depending on the initial aflatoxin content. For practical purposes however, several approaches including acid addition and dehulling rmay be considered for use in reducing aflatoxin levels in maize and maize products whilst bearing in mind the possible nutritional and organoleptic consequences