Malolactic Fermentation (MLF) is a winemaking process in which malic acid is converted to lactic acid. Commonly referred to as secondary fermentation, the process can occur naturally in wine, however winemakers tend to force it by adding lactic acid bacteria (LAB) to the wine.
Depending on the conditions of the wine and the time afforded to the winemaker, the process can occur simultaneously with primary fermentation or immediately after; many winemakers suggest waiting, so as to prevent the conflict of the different conversions within the wine. It generally takes between two to three months for the process to complete. Winemakers monitor the pH levels closely; when the bubbles stop forming and the wine is still, MLF is complete. If a winemaker chooses not to force MLF, they have to take measures to prevent it from occurring later.
Provided by: Wine Frog