On the African continent, tropical cereals such as maize and sorghum are used for the production of beers, since barley (a cool-season, temperate cereal) cultivation is not viable (Taylor, 2003). Moreover, sorghum is the only viable food grain in regions with semi-arid and subtropical climatic conditions (Taylor, 2003). Sorghum beers are widely produced in sub-Saharan Africa and are well-known under their local names, such as burukutu (Nigeria), tchapalo (Ivory Coast), dolo (Burkina Faso), pito (Ghana), munkoyo (Zambia) and bili bili (Chad) (Abegaz, 2007; Faparusi et al., 1973; Lyumugabe et al., 2010, 2013; Marcellin et al., 2009; N'guessan et al., 2011; Nanadoum and Pourquie, 2009; Sawa- dogo-Lingani et al., 2007; Schoustra et al., 2013; Taylor, 2003; van der Aa Ktihle et al., 2001; Zulu et al., 1997). Sorghum beers are traditionally opaque, but some commercial clear versions exist as well (Hibbett and Taylor, 2013; Nanadoum and Pourquie, 2009). These beers are mostly produced by the women of agropastoral families (which perform agriculture by growing crops and keeping livestock) on a weekly basis and are often sold (Dancause et al., 2010). Production methods differ between countries and recipes are often household specific (Taylor, 2003).
As an example, the production of bili bili starts with a malting of the sorghum grains; steeping, germination, and drying of the grains takes about 1 week (Nanadoum and Pourquie, 2009). After the milling of the sorghum malt, the flour is steeped for at least 2 hours, after which the supernatant is removed from the residue (Nanadoum and Pourquie, 2009). The residue is cooked for an average of 2 hours to ensure gelatinization of the starch (Nanadoum and Pourquie, 2009). The thick mash of the residue is mixed with the supernatant at a temperature of 65°C to 70°C. Subsequently, this mixture is left to cool overnight in open air (Nanadoum and Pourquie, 2009). During overnight cooling, the wort acidifies through the action of LAB, which are spontaneously inoculated from either the sorghum malt or from the surrounding air (Nanadoum and Pourquie, 2009). Alternatively, in some sorghum beers, the LAB are introduced by backslopping (Taylor, 2003). In dolo and pito beers, Lactobacillus fermentum is reported as the predominant LAB (Sawadogo-Lingani et al., 2007), whereas in burukutu beer the predominant LAB are identified as Leuconostoc mesenteroides, Lactobacillus plantarum, Lb. brevis, and Lactobacillus delbrueckii (Faparusi et al., 1973). After boiling the acidified wort, either dried yeast obtained from a previous fermentation or backslopping from the previous beer is added to start the fermentation, in which S. cerevisiae dominates (Nanadoum and Pourquie, 2009). This yeast species is dominant in all sorghum beer main fermentation phases, which take place overnight (Faparusi et al., 1973; N'guessan et al., 2011; Nanadoum and Pourquie, 2009; van der Aa Ktihle et al., 2001). The next morning, the beer is ready to be sold and has a shelf-life of about one day (Nanadoum and Pourquie, 2009). In burukutu beer, also a high number ofAAB is found, which are now all classified as Gluconobacter oxydans (Faparusi et al., 1973).