Selection of lactic acid bacteria from home-made sourdoughs for resistance to the main almond skin polyphenols

The aim of this research was to identify lactic acid bacteria (LAB) that could be used as starter strains in sourdough made with almond peel powder to create novel fermented functional bakery products. Physicochemical characteristics and LAB were analyzed from ten home-made sourdoughs used at the family level in western Sicily (Italy). The pH (3.57-4.80) and TTA (8.20-14.20 mL 0.1 N NaOH/10 g) were inversely correlated. LAB dominated all sourdoughs, and the highest cell densities (6.74-9.28 log cfu/g) were detected on the medium Sour Dough Bacteria, except for one sample. Among LAB groups, the lowest counts (4.92-6.19 log cfu/g) were obtained on M17 used for LAB cocci. Yeasts were lower than LAB from two to four orders of magnitude with values between 3.93 and 6.11 log cfu/g. Twenty strains belonging to the species Enterococcus gilvus, Fructilactobacillus sanfranciscensis, Lacticaseibacillus paracasei, Lactiplantibacillus pentosus, Lactiplantibacillus plantarum, Lactococcus lactis, Lentilactobacillus buchneri, Lentilactobacillus diolivorans, Leuconostoc citreum, Leuconostoc holzapfelii, Levilactobacillus brevis, Pediococcus pentosaceus, and Weissella cibaria were identified. Eleven out of the 20 strains identified showed the ability to grow in presence of 16 polyphenols characterizing the peel of almonds. Eight of these LAB strains dropped pH below 4.5 after 6-8 h of fermentation, and two strains showed a strong inhibitory effect against Listeria monocytogenes ATCC19114 with inhibition diameters around the wells >19 mm. Thus, all acidifying strains were selected to produce sourdough bakery goods enriched with almond skin powder.