Optimization and lactic acid bacteria (LAB) characterization of a spelt sourdough for organic bread production

Sourdoughs have been used for centuries as the only starter used to obtain craft products. In the last years, many studies focused to various aspects of sourdoughs production, such as mapping of lactic and yeast microflora, factors that influence fermentative activity of microorganisms, type of products resulting from fermentation of doughs, compounds used by the microbial species and their interactions, microflora evolution during dough’s production and performance of some microrganisms within this particular ecosystem. Purpose of this study was the optimization and LAB characterization of a sourdough obtained using spelt flour for the production of organic bread. The best conditions of time of fermentation, temperature, pH and the amounts of water and flour to obtain a sourdough suitable for baking were choosen. Microbiological analysis were carried out using classical and molecular techniques to have a view of the biodiversity of the lactic acid bacteria during the natural fermentation. Sourdough were collected at different times of fermentation and subjected to traditional and molecular microbiological analysis. After the counts, the plates were used for bulk formation. DNA was extracted directly from the bulks and amplified by PCR and emulsion-PCR (ePCR), using universal primers. DGGE analysis and sequencing of the resulted bands allowed fingerprinting of the microbial populations present in the fermentations. Chemical analysis showed that, in order to obtain a sensorially acceptable bread, pH value of sourdough had to be kept around 4.0. Quantitative determination showed that lactic acid bacteria concentration was higher than the yeasts count values (100:1 ratio), according to what reported in literature. LAB ranged from 103 to 109 cfu/g. Using PCR-DGGE, Lactobacillus sanfranciscensis and Weissella cibaria resulted as the main species involved in the natural fermentation. Conversely, a more complex picture of the involved LAB species was obtained using ePCR-DGGE. For the first time this technique associated with DGGE analysis was applied. The obtained results confirmed the efficiency and usefulness of e-PCR, due to its capacity to avoid preferential amplification in terms of concentration and type of DNA.