Impact of different strains of Saccharomyces cerevisiae on malolactic fermentation by Oenococcus oeni

The ability of different strains of wine yeast (Saccharomyces cerevisiae) to inhibit malolactic bacteria (Oenococcus oeni) was studied using Chardonnay musts. Initial experiments indicated that the bacterial inhibition in a wine fermented by yeast V-1116 could be removed by addition of acetaldehyde or H2O2, compounds that can potentially neutralize the antibacterial properties of any SO2 produced by yeast. Malolactic fermentation was induced in fermenting grape musts or wines inoculated with different commercial strains of S. cerevisiae. Although the yeasts released < 15 to 75 mg/L total SO2, during fermentation, little if any free SO2 ( < 3 mg/L) was produced. As O. oeni was generally inhibited in wines that contained higher amounts of total SO2, the lack of free SO2 suggests that bound SO2 may be more inhibitory than previously thought. Furthermore, bacterial inhibition was strongest in wines where the majority of SO2 was not bound to acetaldehyde but bound to other unidentified molecules. However, SO2 production by yeast did not always account for the inhibition of O. oeni, and the presence of other inhibitory mechanisms is probable.