Abstract: A method is disclosed for deacidifying wine using malolactic fermentation (MLF) under conditions inhibitory for spoillage lactic acid bacteria (LAB), making possible a "pure culture" MLF in which a winemaker is provided with a way to control the timing of onset and the outcome of wine MLF. The method comprises adding nisin to the wine at a concentration lethal to nisin-sensitive LAB, adding to the wine an inoculum of nisin-resistant LAB mutants capable in the presence of nisin of converting malic acid to lactic acid, and maintaining the inoculated wine under conditions in which the MLF can occur. Afterward, nisin can be removed from the wine by contacting the wine with a nisin-removing substance, such as bentonite. The nisin can be added either before or simultaneously with addition of the nisin-resistant LAB, at any time during winemaking, including primary yeast fermentation.