Inhibition of the Malolactic Bacterium,Leuconostoc oenos(PSU-1), by Decanoic Acid and Subsequent Removal of the Inhibition by Yeast Ghosts

The influence of decanoic acid, a metabolite produced by wine yeasts, on the growth and malolactic activity of Leuconostoc oenos (PSU-1) in grape juice was investigated. Decanoic acid was dissolved in ethanol and added to diluted Aurore grape juice before inoculation with Leuconostoc oenos (PSU-1). Although low concentrations of decanoic acid (1 mg/L) did not significantly influence cell viability or the rate of malolactic fermentation (MLF), bacterial growth and MLF were inhibited at acid concentrations of 5.0 to 10.0 mg/L. Rapid bacterial death and complete inhibition of MLF was observed at 30.0 mg/L decanoic acid. Addition of yeast ghosts (1000 mg/L) to juice containing lethal concentrations of decanoic acid was found to remove the bacterial inhibition, presumably by adsorption of the acid.