Aspetti microbiologici del trattamento di acidificazione della vinaccia ed effetti sulla componente aromatica

This work was aimed at focusing the effects of an acidification treatment of grape pomace destined to the production of Grappa, on microbial population and on aromatic compounds after distillation. Grape marcs were acidified up to pH 2,9 at the beginning of the storage period. In order to evaluate the dynamics of the indigenous microorganisms, three different samplings were made, at T0, after 15 days (T15) and after 43 days (T43). Quantification of yeasts and bacteria, evidenced that lowering of the pH limits bacterial growth throughout the ensilage period. Genetic analyses of yeast isolates showed that the species succession lead to non-Saccharomyces species dominance in both conditions although acidified marc showed a lower percentage of Saccharomyces at any sampling time. Gas chromatographic analysis showed a remarkable change in the aromatic profile of distilled grape marcs at the end of the storage, thus evidencing the reduction of the main volatile products associated with potential off-flavours