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  • Population kinetics of yeasts during wine fermentations in Carst and coastal regions of Slovenia
    Povhe Jemec, Katja ...
    The fermentation of grape juice into wine is a heterogeneous microbiological process involving the sequential development of various yeasts and other microbial species, affected by particular ... environment. The population kineticsof yeasts responsible for alcoholic fermentation of musts depends on specific factors such as climate conditions, soil and vine varieties and also viticultural and enological practices used. The aim of our work was the analysis of the yeast population kinetics and genetic diversity during five spontaneous and two induced fermentations of ŸrefoǴkŐ musts in six selected cellars in Karst and coastal wine-producing regions of Slovenia. In autumn 1995, altogether 12 samples of grapes, 36 microbiological smears of cellar equipment and 81 samples of must/wine from different fermentation phases were collected for microbiological and physico-chemical analyses. The total yeast population as well as bacterial and mould contamination of sampleswere determined. Temperature, pH and the concentration of ethanol, sugars, total and volatile acids and SO2 were followed during fermentations. A strong correlation betweenenological interventions (i.e. sulphurization, starter culture application), physico-chemical features of must/wine samples and yeast growth kinetics during fermentations was found. The top of all spontaneous fermentations was reached later than in induced fermentations, but other differences in yeast population dynamics were monitored by intraspecific distinction of Saccharomyces isolates with electrophoretic karyotyping (CHEF PFGE, LKB Pharmacia). Among 469 isolates tested, extremely high inter- and intra-specific heterogeneity was observed on the basis of chromosome length polymorphism of yeasts, isolated during different fermentation stages in spontaneous and also in starter culture induced fermentations. Population composition varied not only between areas but also between cellars in the same area. In the first step of must fermentation, grape flora dominated in all fresh musts but was later overgrown by specific Saccharomyces cerevisiae yeast population. S. cerevisiae strains, which appeared in the first stages of fermentations were usually present at the highest frequency to the end of the processes. Those strains of S. cerevisie (four altogether) were found in all fermentations studied. They seemed to be widely distributed in wine-producing region of Primorska. However, many specific karyotypes were determined for strains isolated from later stages of wine fermentations and many of them were only batch specific. The number of such strains increased during the majority of fermentations. On the other side, we could not determine region-specific yeastpopulation, responsible for the production of ŸrefoǴkŐ and ŸteranŐ wine, produced in geographically different Karst and coastal regions .
    Source: Yeast nutrition and natural habitats : book of abstracts (str. P4-12)
    Type of material - conference contribution
    Publish date - 1997
    Language - english
    COBISS.SI-ID - 1955960

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