Effetti di alcuni trattamenti tecnologici (acidificazione e inoculo di lieviti selezionati) su microflora di vinaccia durante la fase di stoccaggio e implicazioni sulla qualità del distillato.

The present work was aimed at focusing the effects of two acidification treatments of grape pomace destined to the production of Grappa, during the storage period. The first is an acidification treatment, commonly adopted by the distilleries to limit bacterial proliferation, whereas the second is the inoculation with a selected yeast, chosen from a wide pool of isolates collected during previous experimentations. In the first case, non-treated grape marcs were compared with acidified grape marcs up to pH 2,9. In order to evaluate the dynamics of the indigenous microorganisms, three different samplings were made during the storage period (T0, after 15 days and at the end). Quantification of yeasts and bacteria, evidenced that low pH limits bacterial growth throughout the ensilage period. Gas-chromatographic analysis of the distillates obtained from marcs at the end of the storage period, show that the concentration of aromatic compounds is higher in non-acidified than in acidified grape marc. As regards the inoculation of a Saccharomyces cerevisiae yeast, population dynamics monitored at three sampling times showed no differences between control and inoculated pomace. By means of molecular methods, the presence of the inoculated yeast during the first 15 days of storage was assessed.