Abstract
In this study, we explored the diversity of yeasts and lactic acid bacteria (LAB) associated with six spontaneous sourdough fermentations from the northern part of the Apulian region (Italy). Bacterial and yeast isolates from sourdough were investigated by amplified ribosomal DNA restriction analysis (ARDRA) and restriction fragment length polymorphism (RFLP) analysis, respectively. The identification of the isolates was confirmed by sequencing bacterial 16S gene and yeast ITS1–5.8S–ITS2 rRNA gene amplicons. Microbiological analysis of all sourdough samples revealed that LAB and yeast counts ranged between 1.7 × 105 and 6.5 × 108 cfu/g, and 7.7 × 105 and 2.5 × 107 cfu/g, respectively. The molecular identification at species level revealed the occurrence of Lactobacillus plantarum as the dominant LAB and Saccharomyces cerevisiae as the dominant yeast species in all different sourdough samples. Then, the ability of all isolated strains to inhibit and/or reduce the growth of several selected fungi was valued through the overlay method. In light of their antifungal performances, ten LAB strains were inoculated, singularly and in combination, in subsequent bread-making trials. Overall, we confirmed the potential of LAB to extend the shelf life of bread through spoilage inhibition and, for the first time, we observed a synergistic effect due to the combination of several isolated LAB on the inhibition behavior against selected fungal spoilage strains. Our findings suggest the exploration of a LAB-based approach in order to extend the shelf life of bread, reducing, at the same time, the use of chemical agents for food preservation.
Highlights
The manufacturing of several food products is founded on starter culture inoculation
Six Italian sourdoughs collected from different localities, i.e., Monte Sant’Angelo, Orsara di Puglia
The sourdough microbial ratio lactic acid bacteria (LAB):yeasts was 100:1 [9] and for some of the analyzed samples, i.e., B (Orsara di Puglia), D (Trani 02), E (Trani 03) and F (Ortanova), we found this kind of proportion
Summary
The manufacturing of several food products is founded on starter culture inoculation. On the one hand, today the food industry benefits from the numerous signs of progress made in the selection of new and increasingly active microbial starters to drive and standardize the manufacture of fermented foodstuffs, yet on the other hand we should not forget that there are some foods in which this process of microbial selection occurs naturally and gradually, leading to natural starters being independently selected over time This is the case of sourdough that is the combination of flour, water, autochthonous homofermentative and heterofermentative lactic acid bacteria (LAB), and yeasts [2]. The sourdough ecosystem is strictly dependent on factors such as dough hydration, type of cereal source, temperature of fermentation, and geographical area of production [8,9]
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