Four isolated lactic acid bacteria LAB strains Lactobacillus brevis, Lactobacillus plantarum, Pediococcus pentoseus, and Pediococcus acidilactici were selected and used to inoculate sourdough in order to reduce acrylamide content. After fermentation for 16 h, all of the inoculated sourdoughs showed lower pH values compared to the spontaneous sourdough. This acidification was accompanied by a significant (p<0.05) increase in the concentration of reducing sugars. The baked bread samples made with the tested LAB strains showed significantly reduced acrylamide content, in particular for the sample inoculated with P.acidilactici (5.64 µg/kg), compared to the bread sample prepared with baker's yeast (35.6 µg/kg). The resulting breads were also evaluated for several other quality parameters. The highest softness was registered for the breads obtained from the fermentation by P.acidilactici (2704 g). The different tested strains also influenced the color, the void fraction, and the cell density of the breads. The sensory evaluation indicated that the crust color, crumb aeration, as well as the salty and acidic tastes were not significantly affected by sourdough incorporation. However, breads made from LAB sourdoughs were more appreciated by the tasters. This study proved the suitability use of the selected P.acidilactici strain for industrial-scale bread production.

The present work was carried out to identify lactic acid bacteria (LAB) from wheat flours and to evaluate their technological capabilities for potential incorporation in sourdough process. Six samples of baking wheat flours were collected from mills situated in different geographical regions of Tunisia and used for microbiological analysis of total mesophilic aerobic microorganisms, yeasts, moulds and LAB. A total of 45 autochthonous LAB were isolated and identified by genetic analysis of 16S-23S rRNA intergenic transcribed spacer ITS generated patterns ITS-PCR. One representative strain of each ITS-PCR pattern was subjected to partial sequencing of the 16S rRNA. Strains were identified as Weissella cibaria, Lactobacillus plantarum, Lactobacillus brevis, Pediococcus pentosaceus, Pediococcus pentoseus, Pediococcus acidilactici, Enterococcus faecium, Enterococcus casseliflavus and Enterococcus faecalis. Technological features including acidification, antimicrobial, amylolytic, proteolytic and antioxidant activities of six selected LAB strains were investigated for future in situ applications. Moreover, LAB were investigated for their ability to produce exopolysaccharides. All tested LAB showed good acidifying ability by decreasing significantly (p<0.05) the pH of flour extract below 4.0 after 24 h and below 3.0 after 72 h. P. pentoseus and P. acidilactici presented fermentation quotient FQ (ratio of lactic and acetic acids) close to the optimal range. All flour LAB isolates, demonstrated extracellular proteolytic activity. W. cibaria S25 had the highest radical-scavenging activity with a rate of 25.57%. L. plantarum S28 demonstrated the highest amylolytic activity (1386 U/mL) followed by P. acidilactici S16 (1086 U/mL). Although, L. plantarum S28 showed the highest production of exopolysaccharides (0.97 g/L). Moreover, different halo of inhibition were detected against E. coli, Staphylococcus aureus, Aspergillus niger and Penicillium expansum. This study revealed that autochthonous flour LAB exhibited interesting technological features and thus could be used in sourdough production.

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