Aspects of manufacture, composition and safety of orubisi: a traditional alcoholic beverage in the north-western region of Tanzania.

The processing technology and characteristics of orubisi/amarwa, an opaque beer commonly consumed in Kagera region in the north-western part of Tanzania is described in detail. The protein content of orubisi increased from 2.0 to 2.7% after 120 hours of fermentation. The maximum alcohol content of orubisi as determined by specific gravity method was 2.5%. The alcohol profile of orubisi analysed by gas liquid chromatography (GLC) was found to contain ethanol and iso-butanol. The test for methanol was negative. Orubisi was characterised as product with relatively high acidity ranging from 0.35-0.89 g/100 ml and a final pH of 3.7. The levels of fermentable sugars--sucrose, maltose, glucose and fructose--were 0.5, 0.7, 1.8 and 0.6 g/100 ml after 120 hours of fermentation, respectively. High microbial counts were encountered in orubisi. The viable counts included yeasts: 2.0 x 10(7) cfu/ml, moulds 7.4 x 10(6) cfu/ml, coliforms 1.18 x 10(2) cfu/ml, lactic acid bacteria 6.5 x 10(7) cfu/ml and total aerobic count 2.95 x 10(7) cfu/ml. Based on these results, orubisi poses a serious danger to public health due to the presence of high numbers of total count and coliforms. In order to improve the safety of orubisi the pasteurisation step is recommended in the process of preparing orubisi. Hygienic handling of the final product is necessary in order to avoid contamination before consumption. The presence of trace amount of iso-butanol can lead to irritation of mucous membranes and depression of central nervous system.