Evaluation of the simultaneous effects of a heat stabilized starter concentration and the duration of fermentation on the quality of the opaque sorghum beer

This study evaluates the simultaneous effect of dried starter concentration and fermentation duration on the quality characteristics of the African opaque sorghum beer using response surface methodology. The aim was to improve the beer quality and to optimize its fermentation process. Results show that the granule starter concentration and the fermentation duration have significant effects on the dry matter, refractive index, titrable acidity, glucose, raffinose and fructose contents of the beer. The lactic acid bacteria, yeasts and total mesophilic aerobic bacteria counts were significantly modified as a result of these fermentation parameters. The pH was only affected by the fermentation duration. The optimum beer quality could be reached between 10 and 15 h at starter concentration in the interval of 100 to 120 g/L. The use of the dried starter granules revealed to be an efficient alternative to produce sorghum beer with stable quality at a shorter fermentation time. Key words : starter, kpete-kpete, sorghum beer, tchoukoutou.