Malolactic Fermentation - what is it and what does it do?
Updated: Oct 22
Part of our Wine Science series
Malolactic fermentation (MLF or malo) is a natural process that occurs during the winemaking process. It is a secondary fermentation that converts tart malic acid (which is found in grape juice) to softer lactic acid, reducing the wine's acidity and increasing its complexity and flavor.
MLF is typically desired in red wines and some white wines, such as Chardonnay or Viognier. You would not want to induce MLF in a white wine that is meant to be fresh, zingy and high in acidity such as Riesling or Sauvignon Blanc.
During MLF, bacteria convert malic acid into lactic acid, which produces carbon dioxide as a byproduct. This process can occur naturally or can be induced by adding a malolactic culture to the wine. Winemakers can monitor MLF by testing the wine's pH levels and tasting the wine to determine when the process is complete.
The benefits of MLF can include a smoother mouthfeel, increased complexity, and a more rounded flavour profile. However, if the process is not monitored closely, it can lead to unwanted flavors and aromas, such as buttery or cheesy notes in the wine.
MLF is particularly important for red wines with higher levels of tannins and acidity, making them less approachable in their youth. By undergoing MLF, red wines can achieve a more balanced and integrated flavour profile, with that softer mouthfeel. While MLF is typically desired in most red wines, it may not be desirable for white wines or more delicate reds. In these cases, winemakers may choose to block MLF by using sulfites or other techniques to preserve the wine's fresh acidity.
I hope that helps to demystify malolactic fermentation but what else can we demystify? If something confuses you in the world of wine, you can be sure it confuses lots of other people. Let us know what puzzles you and we'll aim to answer the question ..
Tony Elvin - The Wine Events Company