Effect of pH and Sulfur Dioxide on the Rate of Malolactic Fermentation in Red Table Wines

Abstract

The pH of three must samples from Chancellor, a red French hybrid, was adjusted to 3.3, 3.5, and 3.7, respectively. Musts at each pH were treated with 25, 50, and 75 ppm sulfur dioxide, respecitvley, and then inoculated with a wine yeast, <i>Saccharomyces cerevisiae</i> Montrachet #522. When the fermenting musts reached 5°Brix, each was inoculated with a malolactic bacteria, <i>Leuconostoc oenos</i> PSU-1. For each level of SO₂, rates of malolactic fermentation were nearly the same at pH 3.5 and 3.7, but fermentation was much slower at pH 3.3. At a given pH, malolactic fermentation was faster at the lower SO₂ levels. Following inoculation, the bacterial population decreased, and the lowest bacterial count was observed in the presence of low pH and high SO₂.