Malolactic Fermentation (MLF) is a method used to reduce total titratable acidity and raise the pH by adjusting the relative concentrations of L-Malic and L-Lactic Acids, softening the wine and allowing red wine to develop mellowness and full-bodiedness. (Peynaud)
Since grapes do not produce lactic acid, regular monitoring of D-Lactic Acid levels throughout winemaking and aging can be used as an indicator of the onset of bacterial contamination and allows for minimally invasive yet effective control of lactic acid bacteria infections. Contamination is assumed at D-Lactic Acid levels of 300 mg/L or greater.
Since grapes do not produce lactic acid, monitoring for L-Lactic Acid can be used as an indicator of the onset of malolactic fermentation. Having a reliable, on hand test to ensure the onset of MLF solves another problem for winemakers.
Monitor Malic Acid for the progress and completion of malolactic fermentation.
****Wines are put through malolactic fermentation to improve taste and mouthfeel. Red wines with < 30 mg/L malic acid after a full MLF are mellow on the palate and have a full-bodied taste with easy to pick out characters.