The malolactic fermentation: what is it and what for?

You all know the principle of fermentation. To summarize, it is a phenomenon in which yeasts convert sugar into alcohol. This transformation is known since ancient times and is the most important process in wine making. Today this phenomenon known uses as diverse as baking, brewing, wine making or manufacture of biofuel.

But in the wine another fermentation takes place sometimes. This is much less known, because the more discreet (which has notably led to an understanding of the phenomenon later). This is the malolactic fermentation.


We’ll see what is behind this barbaric name and the vital importance of this step in the winemaking.

The malolactic fermentation occurs (usually) once the alcoholic fermentation is completed.
The new wine is cloudy and carbon dioxide will escape clause. Until you ask me, nothing very different from the alcoholic fermentation.
Yet the alcoholic fermentation is well and truly finished and that is another transformation takes place.

What happens is that lactic acid bacteria are found in wine. Note that these bacteria are almost the same as those used to manufacture cheese and other dairy products. Yet here they will not all the same destiny.

By their specific properties in the middle of the wine lactic acid bacteria will transform one of the acids in the grapes into another acid. The malic acid (which is the same as found in green apples) is converted into lactic acid.

A tit for tat you say? No, because lactic acid has the distinction of being less aggressive than malic acid: the wine will be processed and rounder, less harsh and more flexible in the mouth.

Another peculiarity of this phenomenon is the formation of specific odorants. After malolactic fermentation can be collected in the new wine flavors such as whey, butter, hazelnut, etc. …
In addition, the wine has undergone this transformation will be more likely to be retained. Indeed, the risk that the phenomenon is triggered once the bottled wine will be eliminated. Note that if this were the case (which happens sometimes) you’d have a strong odor of gas and milk when you open your wine.

The malolactic fermentation, although rarely reported, is therefore a very important phenomenon in the wine.

It will be sought in most red wines they otherwise would be too aggressive.
In some white wines malolactic fermentation can also be sought. This will mainly wines from northern areas to well marked acidity. The white wines of Long guarde must also undergo this secondary fermentation. But white wine to drink young and for which one seeks a certain freshness does not undergo this transformation, or only partially.