Preliminary study by molecular methods on lactic acid bacteria and yeasts of Calabrian sourdoughs

Sourdough is widely utilized in the production of traditional bread. Lactic acid bacteria (LAB) and yeasts co-exist establishing a dynamic equilibrium that determines the peculiarity of this product as well as its long-term storage. Aim of the present study was to investigate LAB and yeast population of Calabrian sourdoughs. Four sourdoughs collected from bakeries located in Catanzaro (PF1, PF2, and PF4) and in Reggio Calabria (PF5) were tested for pH and total titratable acidity (TTA). For the microbiological analyses, each sample was homogenized, serially diluted, and plated in MRS and SDB for LAB and in YPD for yeasts. DNA was extracted from representative colonies both of LAB and yeasts and subjected to amplification using specific primers [1, 2]. The LAB and the yeasts identification was performed by PCR-ARDRA [3] and by PCR-RFLP [2] comparing the profile isolates to those of reference strains by International collections. Among the sourdoughs, PF1 showed the lowest pH (3.93) and the highest TTA (9.60 ml of NaOH 0.1 N) while the opposite was observed in PF2 (pH: 5.59 and TTA: 2 ml of NaOH 0.1 N). The highest count for LAB was recorded in PF1, PF4, and PF5 (107 CFU/g) and for yeasts in PF1 and PF2 (106 CFU/g). In PF1 and PF5, a dominance of Lactobacillus sanfrancisciensis was observed; in PF2 additionally was observed Pediococcus acidilactici while in PF4 the obtained profiles did not match any of the reference strains considered in this contribution. Concerning the yeasts, Saccharomyces cerevisiae was detected in all the sourdoughs. LAB and yeasts will be tested for technological features to select the best autochthonous strains to use as starter in sourdough production.