Production of organic flavor compounds by dominant lactic acid bacteria and yeasts from Obushera, a traditional sorghum malt fermented beverage.

Single and mixed starter cultures of lactic acid bacteria (LAB): Weissella confusa MNC20, Lactobacillus plantarum MNC21, Lactococcus lactis MNC24 and Lactobacillus fermentum MNC34 and yeasts: Issatchenkia orientalis MNC20Y and Saccharomyces cerevisiae MNC21Y were used to produce Obushera , a fermented sorghum beverage. Microbial counts, pH, sugars, organic acids, and volatile compounds in starter culture and spontaneous fermentations were monitored during 48 hrs. Maximum counts of LAB (8.4-9.4 log cfu g-1 ) and yeasts (7.5 ± 0.1 cfu g-1 ) starter cultures were attained in 6-48 hrs. Weissella confusa , Lc. lactis , and Lb. fermentum showed possible acid sensitivity while I. orientalis produced surface films. LAB starter cultures and their combinations with S. cerevisiae lowered pH from 5.83 to <4.5 (3.50-4.13) in a shorter time (12 hrs) than spontaneous fermentations (24 hrs). Lactococcus lactis and W. confusa metabolized glucose the fastest ( p  < .05) during the first 6 hrs. Lactobacillus fermentum, Lb. plantarum , and S. cerevisiae utilized glucose and maltose concurrently. Lactobacillus plantarum and S. cerevisiae additionally utilized fructose. S. cerevisiae metabolized sugars the fastest ( p  < .05) during the first 12-24 hrs. Lactobacillus plantarum and W. confusa produced the highest ( p  < .05) amounts of lactate (5.43 g kg-1 ) and diacetyl (9.5 mg kg-1 ), respectively. LAB also produced acetate, ethanol, acetaldehyde, acetone, and acetoin. Coculturing LAB with S. cerevisiae reduced ( p  < .05) lactate and diacetyl yield. Yeasts produced high amounts of acetaldehyde and methyl alcohols. Issatchenkia orientalis produced higher ( p  < .05) amounts of 2-methy-1-propanol and 3-methyl-1-butanol than S. cerevisiae . Combinations of LAB with S. cerevisiae produced a profile flavor compounds close to that of spontaneously fermented Obushera . These combinations can be adopted for controlled fermentation of Obushera and related fermented cereal products.