Microbial ecology dynamics in portuguese broa sourdough

This research effort aimed at a better understanding of microbial phenomena taking place during time in spontaneous sourdough fermentation for broa, a traditional Portuguese bread. Unlike most microbiological studies of sourdough, viable counts obtained were not limited to Lactobacillus and yeasts, but encompassed also molds, Gram-negative rods, endospore-(non)forming Gram-positive rods and catalase-positive/negative Gram-positive cocci. This less conventional approach unveiled the ubiquitous Bacillus genus throughout spontaneous broa sourdough fermentation. Presumptive yeasts, Lactobacillus and Bacillus were found to low levels after kneading, but became dominant by the end of regular (no aeration) fermentation. They apparently inhibit undesired rods and Staphylococcus, which were found to relatively high numbers after kneading. By 24 h of fermentation, lactic acid cocci accounted for an important fraction of biodiversity, and pH decreased significantly reaching about 4.1. Aeration accelerated the microbial dynamics. In terms of total viable counts, such a long-term fermentation appeared to reach a quasistationary state.