Microbiological and chemical characterisation of the traditional manufacture of Muratina wine
The microbiological and chemical aspects of the traditional manufacturing process of Muratina (a traditional Kenyan wine) were investigated. The objective was to elucidate the scientific basis of the process. Various aspects of the process were investigated III traditional breweries and in experiments. The wine was obtained by fermentation of sweetened sugarcane juice in the presence of Muratina sponges. These sponges were the fibrous tissues of Murat ina [Fruit ofthe sausage fruit tree (Kigelia afi-icanus)]. It was revealed that colonisation of sponges with yeasts that occurred in naturally fermenting cane juice formed the basis of Muratina manufacture. Sponges were colonized by yeasts in concentrations of 105-106 CFU per gram of their dry matter. This was achieved when sponges were incubated in the juice to condition them to the brewing process. Yeasts were then concentrated to a biomass with a concentration of 109_1011 Colony Forming Units per gram of sponge dry matter, during fermentation. Therefore, sponges were used as inoculants in Muratina fermentation. In raw brews they achieved inoculation in the range of 105 - 108 CFU /ml. This ensured that yeasts dominated the processes from the beginning. Alcoholic fermentation was therefore predetermined. Processes were hence successful irrespective of contamination that came with fresh brews. Fermentation processes required between 1 and 7 days to complete. The matured product contained 2 - 8 %(vol) ethanol, and 0.5 - 1.4 % lactic acid, while its pH lay between 2.7 and 3.2. The use of acidic ingredients and production of acids during fermentation ensured that fermentation processes progressed in acidic environments in between pH 3.0 and 4.0. This limited participants in the fermentation to yeasts and lactic acid bacteria. Due to evolution of ethanol, acids and accompanying changes in pH, bacteria were eliminated so that yeasts dominated the process almost as pure cultures. The maintenance of great yeast numbers in brewing units ensured process successfulness. The capacity of sponges to immobilize the yeasts facilitated this. Recycling sponges between processes ensured adequate inoculation was achieved in every process. On average this was done in twenty-seven brewing cycles before they caused flavour defects in the end product. Consequently, the old culture required disposal by washing sponges in water and then sun drying them. This prepared sponges for re-colonisation in future brewing processes. These aspects formed the basis of Muratina manufacture.