Fermentationstechnologie

Abstrakt

Microbial and Biochemical Changes Occurring During Production of Traditional Rwandese Banana Beer "Urwagwa"

Parawira Wilson, Tusiime David and Binomugisha Sam

Banana beer, urwagwa, is one of the oldest and major alcoholic beverages traditionally processed in Rwanda produced mainly at homes as a family business. The banana beer is manufactured from fermentation of bananas which is an important crop economically and culturally in Rwanda. The processing methods of urwagwa have not yet improved and traditional methods are still in use. Microbial and biochemical changes that occur during production of traditional Rwandese banana beer were investigated in this study. Understanding the microbiological and physicochemical changes is essential in attempts to upgrade the traditional processing commonly used to commercial scale. Banana ripening, extraction of juice from banana and fermentation to produce beer was done using modified traditional methods. During fermentation to produce banana beer, total aerobic mesophilic bacteria, lactic acid bacteria, yeast and molds increased with fermentation time. The presence of high numbers of yeast and lactic acid bacteria (3.12 x 109 and 4.12 x 1013 cfu/ml, respectively) shows that the natural fermentation was a mixed alcohol and lactic acid fermentation. Titratable acidity increased from 0.18 % lactic acid to 0.9 % lactic acid, pH decreased from 4.78 to 4.0, while alcohol concentration increased to 7% v/v after 72h fermentation time. These results give an insight into the microbial and biochemical changes during traditional fermentation processes which is important in attempts to upgrade it to pilot and commercial scale. The study could serve as a starting point for a scientific understanding of the microbiological and physico-chemical processes in urwagwa production with the aim of improving the efficiencyof the production.