Lactic Acid Bacteria and Yeasts in Spontaneously Fermented Sorghum Sourdough

Abstract

Introduction: Generally, natural fermentations are carried out by yeast and lactic acid bacteria forming a complex microbiota that acts in cooperation. Yeast have a prominent role in the production of beverages, due to the ability to accumulate high levels of ethanol and to produce highly desirable aroma compounds, but lactic acid bacteria are particularly important in fermentation because they produce desirable acids, flavor compounds, and peptides that inhibit the growth of undesirable organisms [1]. Studies on the ecology of sourdough microflora may help in the understanding of the microbial dynamics and differences between groups of closely related microbial population in cereal (sourdough) fermentations. In most natural fermentation, starters used are poorly known [2]. Methodology: Lactic acid bacteria and yeasts were isolated from Sourdoughsusing pour plating methods as described by Harrigan and McCance [3]. Mann Rogosa Sharpe (MRS) and potato dextrose medium were used for culturing lactic acid bacteria and yeasts respectively. Cultured MRS plates were incubated anaerobically at 30°C for 48h while that of PDA plates were incubated in an incubator at 25°C for 72h. The microbial populations of the sourdoughs were enumerated on each day of fermentation. Isolation and sub-culturing was done until pure cultures were obtained. Result: The spontaneously fermentative lactic acid bacteria and yeast populating the fermenting sorghum sourdough observed in this study increased rapidly as the fermentation time increased. The mutual or synergistic relationship between the duo confirmed and justified Wood (2004) report in fermenting food matrix. Wood and Hodge (1985), describe the co-existence of lactic acid bacteria and yeast in food processing as very crucial. Conclusion: The microbiological and physicochemical analysis of sorghum sourdough fermented spontaneously showed a synergistic relationship of lactic acid bacterial and yeast growing in it. The titratable acidity, pH, and temperature of the fermenting sorghum sourdough increased with increase days of fermentation with higher values observed in sorghum vulgare.