ena-STUDY-Department of Agriculture-15-05-2018-15:45:08:963-24
Molecular, pro-technological and functional characterization of yeasts isolated from Tuscan sourdoughs to be used as potential starters
Here, yeast populations of traditional sourdoughs collected from four Tuscan bakeries were investigated. Among 200 isolated strains, 78 were randomly selected and molecularly characterized. Saccharomyces cerevisiae was dominant, representing the only species detected in three out of the four sourdoughs. The fourth one harboured also Kazachstania humilis. Inter-delta regions analysis revealed a high intraspecific polymorphism discriminating 16 biotypes of S. cerevisiae isolates, which clustered based on their origin. Representative isolates from each biotype group were singly used to ferment soft and durum wheat flour, aiming at evaluating their pro-technological and functional properties. During fermentation under standardized conditions, all strains were able to grow of ca. 2 log cycles, but only S. cerevisiae L10Y, D18Y and D20Y had a significantly shorter latency phase in both flours. Overall, the highest volumes were reached after 16h of fermentation in both soft and durum fermented dough. S. cerevisiae D2Y and D6Y produced the highest dough volume increase. K. humilis G23Y was the only strain able to increase the total free amino acids concentration of the doughs. Overall, values of phytase activity were significantly (P<0.05) higher in durum compared to the corresponding soft fermented dough. K. humilis G23Y and S. cerevisiae D20Y, D24Y showed a three times higher phytase activity than spontaneously fermented control, and the highest concentration of total phenols. Almost all the strains led to increases of antioxidant activity, without significant differences among them. Besides the evaluation of the properties related to bakery applications, the resistance of the strains to simulated gastric and intestinal conditions, that is considered a pre-requisite for the selection of probiotics, was also investigated, revealing a relevant in vitro survival for many of the strains considered.
Here, yeast populations of traditional sourdoughs collected from four Tuscan bakeries were investigated. Among 200 isolated strains, 78 were randomly selected and molecularly characterized. Saccharomyces cerevisiae was dominant, representing the only species detected in three out of the four sourdoughs. The fourth one harboured also Kazachstania humilis. Inter-delta regions analysis revealed a high intraspecific polymorphism discriminating 16 biotypes of S. cerevisiae isolates, which clustered based on their origin. Representative isolates from each biotype group were singly used to ferment soft and durum wheat flour, aiming at evaluating their pro-technological and functional properties. During fermentation under standardized conditions, all strains were able to grow of ca. 2 log cycles, but only S. cerevisiae L10Y, D18Y and D20Y had a significantly shorter latency phase in both flours. Overall, the highest volumes were reached after 16h of fermentation in both soft and durum fermented dough. S. cerevisiae D2Y and D6Y produced the highest dough volume increase. K. humilis G23Y was the only strain able to increase the total free amino acids concentration of the doughs. Overall, values of phytase activity were significantly (P<0.05) higher in durum compared to the corresponding soft fermented dough. K. humilis G23Y and S. cerevisiae D20Y, D24Y showed a three times higher phytase activity than spontaneously fermented control, and the highest concentration of total phenols. Almost all the strains led to increases of antioxidant activity, without significant differences among them. Besides the evaluation of the properties related to bakery applications, the resistance of the strains to simulated gastric and intestinal conditions, that is considered a pre-requisite for the selection of probiotics, was also investigated, revealing a relevant in vitro survival for many of the strains considered.