African traditional brews: how safe are they?

Abstract

Several African traditional brews have been analysed for their alcohol and sugar content, acidity, fermentation by-products, heavy metals and other contaminants. Alcohol levels are variable and the highest was found in moonshine (21–44% v v ). Parameters such as methanol, fusel oils, aldehydes, esters and heavy metals have often been found to be above permitted WHO standards for drinking water. High contaminant levels occur in moonshine: methanol (18–152 ppm), butanol (200–800 ppm), propanol (39–75 ppm), esters (1.3–8.6 ppm) and copper (up to 31.2 ppm). Acidities of up to 80.2 mmol/litre are attained in some brands. The apparent high ester levels in banana brew are due to iso-amyl acetate in banana aroma. Sugar levels have been found to diminish, whereas acidity increases on ageing. For some brands, it is shown that the end of useful fermentation is approximately 17 h at 30 °C and, beyond this, quality deterioration predominates. This is therefore recommended as a maximum safe shelf-life for human consumption. Metal uptake from surfaces is enhanced by high acidity, long shelf-life and high temperature. Higher alcohol content enhances copper uptake, whilst zinc, iron and copper uptake diminish with increasing sugar and alcohol contents. Handling in iron or galvanized ironware is shown to deplete copper by almost 100% of initial levels and this has potential in health risk reduction applications.