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 aflatoxins 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 aflatoxins destruction. The addition of citric and phospheric 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 3.5-1.3. Subsequent cooking of the slurry resulted in further reductions in aflatoxin B₁ and B₂ levels. Dehulling of maize kernels as done during the preparation of abolo (a slightly fermented and steamed maize product) appeared to give a pronounced reduction in aflatoxins content which could be up to 86% depending on the the initial aflatoxins content. For practical purposes however, several approaches including acid addition and dehulling may be considered for use in reducing aflatoxin levels in maize and maize products whilst bearing in mind the possible nutritional and organoleptic consequences