I’ve written an essay about malolactic fermentation as my first MW assignment. I wanted to share a simple and shorter version of it for those who are interested:
So, let’s start with the definition of Malolactic Fermentation (MLF)!
MLF is a winemaking process where malic acid is converted into soft-tasting lactic acid. It is also known as secondary fermentation or malolactic conversion. It occurs mostly during red winemaking process and some white wine production. The application or absence of MLF depends on the desired wine style because it results in several changes in wine such as: acidity structure, stability of wine, and flavour profile.
Before discussing the effects of MLF on wine style, it is crucial to understand how this process works. Initially, MLF converts malic acid to lactic acid and carbon dioxide. During this process, titratable acidity levels are reduced (typically around 0.1 – 0.3 g/ 100 mL) With this, a small increase in pH occurs as well. This conversion is done by lactic acid bacteria that are active between 2.9 – 3.6 pH and above 15 C. (up to 37 C) High levels of sulphur dioxide and ethanol inhibits their activity.
Here are the main outcomes of MLF:
MLF transfers harsh-tasting malic acid to softer-tasting lactic acid and decreases the titratable acidity (TA). This means that the tart taste of wine is perceived less in wine. This softening is an advantage for red wines as it gives smoothness. Therefore, most of the winemakers make sure that red wines complete MLF before bottling. For the white wines, it depends more on the style of the wine which will be mentioned shortly.
Another result of MLF is more stability in wine. Without MLF, the wine might go through MLF in the bottle. If this happens, it will create turbidity due to cell growth. The by-product carbon dioxide will dissolve in wine and make it fizzy. The winemaker will lose the control of flavour profile. For this reason, having MLF done before bottling creates more stability in wine. Furthermore, the lactic acid bacteria consume nutrients that might be otherwise available for other harmful organisms.
MLF is known to add complexity and flavours both to red and white wine. Flavour changes are associated with the production of certain compounds such as diacetyl. Diacetyl around 1-4 mg/L creates buttery flavors. If it exceets 4mg/L it gives more rancid flavor. There are also other compounds that can affect the taste of the wine. For instance 2,3 Butantediol or acrolein can lead to a bitter finish on wine.
Now that we know the results of MLF, we can have a look at wine styles with or without MLF:
For red wines, winemakers mostly prefer to do malolactic fermentation, even if the wine has low acidity. It makes the taste smoother and keeps the wine stable especially if it is going to age in barrels for the following months. Also, the risk of malolactic conversion in the bottle would be eliminated and the winemaking doesn’t have to do sterile filter (where he/she loses other flavours) or add preservatives to protect the wine from bacteria growth.
In terms of white wines, grape varieties such as Riesling, Gewürtztraminer, Pinot Gris, Sauvignon Blanc, Chenin Blanc, Muscat show more fruity, floral profile with high acidity. Using malolactic fermentation would completely change the natural style of these wines, especially from countries like Germany, Austria, France, New Zealand. Therefore, the winemakers usually protect these wines from MLF.
In white wines, Chardonnay is a grape variety that is more appropriate for MLF. If we have a look at Chardonnay’s from California, the wines have a character of vanilla, butter and can be described as oily and smooth. They are mostly rounder with creamy-feeling wine that shows the effects of MLF. On the other hand, it is important to mention that there are many Chardonnay’s in the world including California that are crispy showing citrus, green apple aromas without any MLF. According to the recent panel tasting in Decanter, Andy Howard MW mentions that the trend is shifting away from big bold wines to fresher and crispy model.
Another important region of Chardonnay is indeed Burgundy. In Chablis, one of France’s coolest regions, Chardonnay’s have a particular flavour structure with wet stones and citrusy, green fruits. Chardonnay does not easily ripen and the wines are mostly refreshing, higher in acidity and lighter in body. MLF is not very common in Chablis as it is in Cote d’Or. Whites of Burgundy mostly go through MLF. However, it is also important to mention that, the acidity is still high after MLF in white Burgundy compared to California. This is simply because of the climate conditions.
The white wines of Switzerland are another interesting example in discussing malolactic fermentation. As is known, Switzerland is a cool winegrowing region and the most planted white varieties are Chasselas, Muller-Thurgau, Chardonnay, Sylvaner, Pinot Gris. The natural acidity of the wines in this region is usually very high. As a tradition in Switzerland, white wines go through full malolactic fermentation. However, sometimes this can result in flabby wines. Recently, some young winemakers started avoiding MLF or using only partial MLF and this provides the winemaker to have a better balance in wine
In addition to red wines and certain white wines, sparkling wines also go through MLF. The base needs to be as stable as it can be before second fermentation takes place in the bottle or in tank.
There are always exceptions as winemakers experiment constantly around the world. However, we summarized the aspects of MLF and went through different types of wine styles with or without MLF. Overall, if the primary fruit flavours and the acidity are important for the wine, MLF is avoided. On the other hand, some white wines benefit from MLF to attain buttery flavours and less sharp acidity. Red wines and sparkling wines mostly go through MLF for smoothness and stability. There are also producers who apply partial MLF to reach the best balance. It is always about creating the best balance in my opinion, considering the nature and the potential of the wine.