Quality Evaluation of Naturally Fermented Alcoholic Beverages, Microbiological Examination of Source of Fermentation and Ethanol Productivity of the Isolates

The naturally fermented alcoholic (NFA) beverages collected from tribal areas contained higher quantity of methanol, with wide variations in ethanol, pH and volatile acidity. The NFA beverages were also found to be contaminated with Brettanomyces spp. and coliform bacteria indicating a potential danger of their consumption. The examination of natural sources of fermentation (NSF), frequently used in such fermentations, revealed the presence of fungi viz., Aspergillus flavus, Aspergillus oryzae, Mucor spp., Rhizopus spp.: the yeast included Saccharomyces spp., Scytalidium thermophilus (Torula) and Rhodotorula and bacteria viz., Pediococcus, Leuconostoc and Pseudomonas. Except for a few, the general ethanol productivity of the isolates from NSF was low. Saccharomyces spp. had higher population and was predominant among the yeasts isolated from NSF. The abnormal characteristics of the NFA beverages could be correlated with the raw materials, source and method of fermentation and distillation. Use of pure yeast and proper distillation method could improve the quality of such beverages.