Munkoyo beverage, a traditional Zambian fermented maize gruel using Rhynchosia root as amylase source

A typical munkoyo beverage was made by fermenting Rhynchosia heterophylla root extract-cooked maize meal mixture with Lactobacillus confusus LZ1 and Saccharomyces cerevisiae YZ20. The fermented munkoyo beverage had a pH of 3.3, lactic acid content of 60 mmol/l, ethanol 320-410 mmol/l and a characteristic 'munkoyo' aroma. L. confusus, used alone, produced a beverage with a faint munkoyo flavour note whilst beverage produced with S. cerevisiae alone seemed not to have a typical munkoyo note. R. heterophylla root extract converted 75% of the starch in sterile cooked maize meal to maltose (80% of total sugars), maltotriose (17%) and glucose (3%) in 1 h at 45°C. During fermentation by the mixed culture or the yeast alone most of the maltose was utilised but little or none of the maltotriose. The ratio of yeast to lactic acid bacteria in the starter culture affected the rate of production of ethanol but had no effect on the growth or acid production by the bacterium. To obtain a munkoyo beverage with the desired low alcohol concentration (< 100 mmol/l), the ratio of yeast concentration (cfu/ml) to Lactobacillus concentration in the starter culture should be 1:1000 or less and the beverage should be fermented for 24 h only.