Malolactic fermentation (MLF) is typically carried out in most red wines and in some white varietals. MLF plays an important role in the finished wine’s feel and taste. MLF reduces acidity and produces flavors often characterized as “soft” or “buttery”. In addition, carrying out MLF before bottling prevents an unintended development of carbon dioxide gas (CO2) due to MLF starting up in the bottle, which can lead to fizzy wine, or worse, exploding bottles!
Malolactic fermentation uses the beneficial bacterium Oenococcus oeni (O. oeni) to convert malic acid to lactic acid, and CO2:
Malic Acid O. oeni Lactic Acid + carbon dioxide
HOOC–CH2–CH(OH)–COOH CH3–CH(OH)–COOH + CO2
Sulfite, as free SO2, inhibits the O. oeni’s activity, so free SO2 levels must be kept low during MLF. This leaves the wine at risk of oxidation and microbial contamination. As soon as MLF is done, then, SO2 should be raised to appropriate levels for protection of the wine. Thus it is important to know when MLF is done, and the best way to do this is to measure malic acid levels in the wine.
Should I do MLF?
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