Idrolisi di precursori d’aroma glicosilati nel corso della fermentazione malolattica

The ability of four commercial preparations of Oenococcus oeni lactic acid bacteria (EQ 54, Lalvin O.S.U., Uvaferm Alpha, and Lalvin 31) to hydrolyse wine aroma precursors was evaluated by measuring the concentration of free and bound aroma compounds at the end of malolactic fermentation carried out in model wines containing a mixture of glycosides extracted from Muscat wine. At pH 3,4 there was a decrease in glycosylated compounds matched by a concomitant increase in free forms in all starter cultures tested. When malolactic fermentation was carried out at pH 3,2 a significant decrease in the ability to hydrolyse aroma precursors was observed for two of the cultures tested (Uvaferm Alpha and Lalvin 31). Large differences in the extent of hydrolysis and in the specificity of this activity towards specific aroma precursors were observed, and appeared related to the chemical structure of the aglycon as well as to individual characteristics of each starter culture. The amounts of glycosylated aroma compounds released during malolactic fermentation suggest that O. oeni can alter the sensory characteristics of wine through the hydrolysis of aroma precursors.