Abstract
AbstractThis 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 ApplicationsMicrobial 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.
Highlights
Sourdough has been used since ancient times in food processing; it is one of the oldest biotechnological processes employed by Man
While to our knowledge no public case exists of food poisoning arising from consumption of broa, our results showed that fermentation constitutes a critical control point, and increasing the broa fermentation period would be a good manufacturing practice to increase food safety
High total viable counts were reached by 2 days of fermentation, Staphylococcus vanished by this time
Summary
Sourdough has been used since ancient times in food processing; it is one of the oldest biotechnological processes employed by Man. Bread and related products manufactured without baker’s yeast resort to a sour ferment. Examples of such breads encompass Portuguese broa (Rocha et al 2003; Rocha 2011; Rocha and Malcata 2012, 2015), Finnish sour-rye bread (Salovaara and Hatunp€a€a 1984), German rye bread (Spicher and Werner 1988), San Francisco sourdough French bread (Kline and Sugihara 1971) and soda crackers (Sugihara 1985), wheat Italian panettone (Ottogalli et al 1996), Italian pandoro (Zorzanello and Sugihara 1982) and colomba (Sugihara 1977), Iranian Sangak bread (Azar et al 1977), and Sudanese Kisra (Abdalla et al 1988; Osman et al 2010), among other varieties found in Arabic and African countries and India, such as lavash, injera, idli and dhokla (Antony et al 1996; Salovaara 1998)
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