Yeasts in the traditional brewing of pito in Ghana

Yeasts from pito, a cereal-based traditional alcoholic beverage were isolated and characterized using biochemical and physiological tests. A total of 21 strains belonging to 8 genera were identified as Saccharomyces cerevisiae (8), Candida tropicalis (4), Kloeckera apiculata (2), Hansenula anomala (2), Torulaspora delbrueckii (3), Schizosaccharomyces pombe (1) and Kluvyeromyces africanus (1). Various diluents used for a 2 h holding period shows that 0.1% malt extract and peptone gave < 20% decrease in cell viability for all the isolates, while phosphate buffer least supported the survival of the yeast cells with about 90% decrease in cell viability obtained for S. pombe at the end of the 2 h holding period. The effect of pH and temperature on the growth of the isolates revealed that at relatively low temperatures, growth increased with increasing pH, but a decrease was observed with increasing pH at high temperatures for S. cerevisiae and Candida tropicalis. All the isolates demonstrated good growth (10(2) to 10(6) c.f.u./ml) at 10% ethanol concentration over a period of 8 days incubation. However, growth of K. africanus was completely inhibited after 4 days incubation period. The quality indices of the beverage produced using S. cerevisiae as a single-starter organism compared favourably with the traditional brew. The paper suggests ways of scientifically regulating the production of fermented foods in sub-Saharan Africa.