Microbial Ecology Dynamics in Portuguese Broa Sourdough

• Published in: Journal of food quality 2016-12, Vol.39 (6), p.634-648
• Main Authors: Rocha, João M., Malcata, F. Xavier
• Format: Article
• Language: English
• Subjects: Aeration; Bacillus; Counting; Dynamics; Fermentation; Lactobacillus; Microorganisms; Rods; Sourdough; Staphylococcus; Zea mays
• ISSN: 0146-9428; 1745-4557
• DOI: 10.1111/jfq.12244

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 quasi‐stationary state. Practical Applications Microbial studies encompassing a large set of culture media and incubation conditions were previously undertaken in samples of maize and rye flours, and sourdoughs for broa obtained from 14 artisanal producers and in two seasons. Microbial counts and identification unfolded a complex wild microbiota, and fermentation played a major effect upon all microbial groups. Flours and mother‐dough microbiota were characterized during storage afterward. A similar approach was followed here to ascertain the microbiological profile of a wide range of microorganisms throughout long‐term sourdough fermentation, in attempts to answer the questions: how microorganisms evolve, and how they respond to increasing aeration. These studies provide an innovative way to look at sourdough systems and microbial dynamics therein. Results showed the importance of increasing fermentation time to take full advantage of ecological competition against undesirable microorganisms, and emphasized the need for further studies to reveal the role of Bacillus in sourdough fermentations.