Seven mature type I sourdoughs were comparatively back-slopped (80 days) at artisan bakery and laboratory levels under constant technology parameters. The cell density of presumptive lactic acid bacteria and related biochemical features were not affected by the environment of propagation. On the contrary, the number of yeasts markedly decreased from artisan bakery to laboratory propagation. During late laboratory propagation, denaturing gradient gel electrophoresis (DGGE) showed that the DNA band corresponding to Saccharomyces cerevisiae was no longer detectable in several sourdoughs. Twelve species of lactic acid bacteria were variously identified through a culture-dependent approach. All sourdoughs harbored a certain number of species and strains, which were dominant throughout time and, in several cases, varied depending on the environment of propagation. As shown by statistical permutation analysis, the lactic acid bacterium populations differed among sourdoughs propagated at artisan bakery and laboratory levels. Lactobacillus plantarum, Lactobacillus sakei, and Weissella cibaria dominated in only some sourdoughs back-slopped at artisan bakeries, and Leuconostoc citreum seemed to be more persistent under laboratory conditions. Strains of Lactobacillus sanfranciscensis were indifferently found in some sourdoughs. Together with the other stable species and strains, other lactic acid bacteria temporarily contaminated the sourdoughs and largely differed between artisan bakery and laboratory levels. The environment of propagation has an undoubted influence on the composition of sourdough yeast and lactic acid bacterium microbiotas.
Many studies have undoubtedly demonstrated the nutritional, sensory, texture, and shelf-life advantages of using sourdough for the manufacture of baked goods (14). Nowadays, sourdough is largely used for making wheat and rye breads, crackers, pizza, various sweet baked goods, and gluten-free products (2,14,20).Based on the biotechnology protocol, sourdough fermentations are usually classified into three types (types I, II, and III) (48). Type I, or traditional, sourdoughs are characterized by continuous (daily) propagation (back-slopping) of the dough at ambient temperatures (20 to 30°C). Typical and traditional Italian breads are mainly made using sourdoughs belonging to type I (27), and, in most cases, only one back-slopping per day is carried out (26,27). A microbial consortium mainly consisting of obligately and/or facultatively heterofermentative lactobacilli and yeasts usually dominates the mature sourdough (48). For sourdoughs made with various cereals, the stable population of lactic acid bacteria seemed to occur through a three-phase evolution within a few days of back-slopping (45). Nevertheless, the stability of the mature sourdough depends on a number of factors, which include the environmental microbiota (e.g., flour and other ingredients, house microbiota), its metabolic activity (e.g., amylase activity, cofactor regeneration capability, and energy synthesis from various ...