Lactic Acid Bacterium and Yeast Microbiotas of 19 Sourdoughs Used for Traditional/Typical Italian Breads: Interactions between Ingredients and Microbial Species Diversity

Abstract

The study of the microbiotas of 19 Italian sourdoughs used for the manufacture of traditional/typical breads allowed the identification, through a culture-dependent approach, of 20 and 4 species of lactic acid bacteria (LAB) and yeasts, respectively. Numerically, the most frequent LAB isolates were Lactobacillus sanfranciscensis (ca. 28% of the total LAB isolates), Lactobacillus plantarum (ca. 16%), and Lactobacillus paralimentarius (ca. 14%). Saccharomyces cerevisiae was identified in 16 sourdoughs. Candida humilis, Kazachstania barnettii, and Kazachstania exigua were also identified. As shown by principal component analysis (PCA), a correlation was found between the ingredients, especially the type of flour, the microbial community, and the biochemical features of sourdoughs. Triticum durum flours were characterized by the high level of maltose, glucose, fructose, and free amino acids (FAA) correlated with the sole or main presence of obligately heterofermentative LAB, the lowest number of facultatively heterofermentative strains, and the low cell density of yeasts in the mature sourdoughs. This study highlighted, through a comprehensive and comparative approach, the dominant microbiotas of 19 Italian sourdoughs, which determined some of the peculiarities of the resulting traditional/typical Italian breads. During the last decades, European and worldwide consumers have come ever more to appreciate traditional and typical foods. Traditional is the definition used for foods that historically are part of the cultural heritage of people living in a certain geographical area (29a). Typical is the attribute used for a food produced using one or more ingredients having characteristics strictly depending on the geographical area it comes from (9). Mainly due to the long history of regional political division, about 200 different types of bread are manufactured throughout Italy with large differences of recipes and traditions (24). Some breads have already received the Protected Designation of Origin (PDO) (Pane di Altamura and Pagnotta del Dittaino) or the Protected Geographical Indication (PGI) (Pane di Matera, Pane Casareccio di Genzano, and Coppia Ferrarese). In spite of the differences, almost all traditional/typical Italian breads use sourdough as the natural starter. Sourdough represents a very complex biological ecosystem (19) where yeasts and, especially, lactic acid bacteria (LAB) largely determine the sensory, technology, nutritional, and functional features of the resulting baked goods (20). In mature sourdoughs, LAB occur in numbers Ͼ10 8 CFU g Ϫ1 , whereas the number of yeasts is at least one order of magnitude lower (19). The microbial composition of the sourdough was subjected to numerous studies which have revealed a large species diversity (for reviews, see references 15, 16, 22, and 43). Overall, Lactobacillus brevis, Lactobacillus paralimentarius, Lactobacillus plantarum, Lactobacillus rossiae, and Lactobacillus sanfranciscensis dominate sourdough processes that are characterized by low incubation t...

Codominance of Lactobacillus plantarum and obligate heterofermentative lactic acid bacteria during sourdough fermentation

“…The levels of LAB estimated on SDB were above 10 8 CFU g À1 for the majority of samples indicating the dominance of this group of bacteria. The levels of LAB detected in this study were reported for other sourdough samples produced in Sicily (Minervini et al, 2012). Yeasts were also counted and, for many sourdoughs, yeast/LAB ratio was almost 1:100 which is in agreement with those reported in literature for type I sourdoughs (Gobbetti et al, 1994;Ottogalli et al, 1996;Valmorri et al, 2006).…”

“…The majority of LAB screened and selected to act as starters in sourdough production belong to OHe species (Minervini et al, 2012;Settanni et al, 2013). In general, FHe LAB are reported to be found at lower cell densities than the OHe species (Minervini et al, 2012).…”

“…The general characteristics of the sourdoughs collected in western Sicily were determined by the measure of pH, TTA and the chromatographic analyses of lactic and acetic acid. The majority of samples showed an acidity level typical for sourdoughs produced in Italy (Minervini et al, 2012). However, the concentrations of lactic and acetic acid revealed that the FQ of only seven sourdoughs was in the range 1.5e4, considered to affect positively the aroma profile Results indicate mean values of three measurements and are expressed as relative peak areas (peak area of each compound/total area) Â l00.…”

Development of a method for the direct fermentation of semolina by selected sourdough lactic acid bacteria

“…The values of pH and TTA registered after fermentation were comparable to those commonly found in mature durum wheat sourdoughs (Minervini et al, 2012a;Pepe et al, 2013;Rizzello et al, 2015;Ventimiglia et al, 2015). Thus, regarding the acidification of the doughs, the liquid starter culture behaved like a mature sourdough inoculum.…”

“…However, after the fermentation with the starter inocula, the microbiological counts increased consistently in almost all sourdoughs. Independently on the microbiological characteristics of the semolina, the addition of the multi-species culture in form of liquid inoculum prepared in SSE determined the development of high numbers of LAB until the levels commonly found in mature sourdoughs produced in Sicily (Minervini et al, 2012a;Ventimiglia et al, 2015), confirming that the method developed in this study is effective for the development of sourdoughs. However, the recognition of the added strains was necessary to state that the cultures added with the liquid inocula dominated the fermentation process over the indigenous LAB hosted in semolina.…”