Winemaking - Malolactic Fermentation

Malolactic Fermentation

Malolactic fermentation occurs when lactic acid bacteria metabolize malic acid and produce lactic acid and carbon dioxide. This is carried out either as an intentional procedure in which specially cultivated strains of such bacteria are introduced into the maturing wine, or it can happen by chance if uncultivated lactic acid bacteria are present.

Malolactic fermentation can improve the taste of wine that has high levels of malic acid, because malic acid, in higher concentration, generally causes an unpleasant harsh and bitter taste sensation, whereas lactic acid is more gentle and less sour. Lactic acid is an acid found in dairy products. Malolactic fermentation usually results in an increase on the pH of the wine. This should be monitored and not allowed to rise above a pH of 3.55, tartaric acid addition is used. The use of lactic acid bacteria is the reason why some chardonnays can taste "buttery" due to the production of diacetyl by the bacteria. All red wines go through complete malolactic fermentation, both to lessen the acid of the wine and to remove the possibility that malolactic fermentation will occur in the bottle. White wines vary in the use of malolactic fermentation during their making. Lighter aromatic wines such as Riesling, generally do not go through malolactic fermentation. The fuller white wines such as barrel fermented chardonnay, are more commonly put through malolactic fermentation. Sometimes a partial fermentation, for example, somewhere less than 50% might be employed.