Malolactic Fermentation

Malolactic Fermentation: The "Softening" Fermentation

Malolactic Fermentation (MLF) is a process where malic acid (the sharp, tart acid found in fruits like green apples) is converted into lactic acid (the softer, creamier acid found in dairy products like milk). This secondary fermentation often happens after the primary fermentation of wine and plays a key role in softening the wine's acidity while contributing to flavor complexity.

How Malolactic Fermentation Works

1. Post-Primary Fermentation – After the initial fermentation, where the yeast has converted sugars into alcohol, the wine is left to undergo MLF.
2. Bacterial Action – The process is carried out by lactic acid bacteria (such as Oenococcus oeni) that are naturally present or added to the wine. These bacteria consume malic acid and convert it into lactic acid and carbon dioxide.
3. Temperature & Environment – MLF usually takes place at a higher temperature (around 65-75°F / 18-24°C) in barrels or stainless steel tanks.
4. Completion – The process takes anywhere from a few weeks to a few months, and once complete, the wine has a softer acidity, often with a rounder mouthfeel