It seems that some people are interested not only in the "taste" of wine, but also in its "production process."
Listening to winemakers, reading high-level wine magazines, participating in seminars by renowned instructors... making an active effort to gain wine knowledge is truly wonderful.
However, there is no shortage of people who end up thinking, "In the end, I didn't really understand it..." because there are simply too many technical terms.
To deepen your knowledge of winemaking, it is necessary to first understand "basic terminology."
This time, let us introduce one of those wine terms that people seem to know yet do not fully understand: "Malolactic Fermentation."
About Malolactic Fermentation
Malolactic fermentation.
This is one of the terms frequently heard when discussing wine production.
In magazines and other media, it is often abbreviated as "MLF", which makes it seem even more incomprehensible.
When you hear things like "underwent MLF," "a short MLF," or "this MLF used a lactic acid bacteria starter," you might completely lose track of the conversation.
Setting aside the effects of malolactic fermentation for later, let us first look at what malolactic fermentation actually is.
What Is Malolactic Fermentation?
Malolactic fermentation is a production process conducted to soften the acidity of wine and mellow its aroma and flavor.
It is mainly adopted for red wines (and some white wines) and is carried out after alcoholic fermentation.
For example, red wine is an alcoholic beverage with strong astringency, which does not pair well with strong acidity.
Due to the nature of red wine, alcoholic fermentation alone leaves behind pronounced acidity, so malolactic fermentation is carried out to balance the flavor.
Now, you probably understand the surface-level idea, but why does conducting malolactic fermentation soften the wine's acidity?
The Mechanism of Malolactic Fermentation
The main player in alcoholic fermentation is "yeast," but the main player in malolactic fermentation is "lactic acid bacteria."
Wine must contains a component related to tartness called "L-malic acid," but when malolactic fermentation takes place, the action of malolactic enzyme decarboxylates the L-malic acid, converting it into "L-lactic acid."
It might sound a bit complicated, but...
Start of malolactic fermentation
↓
L-malate ions in the must enter the lactic acid bacterial cells
↓
Decarboxylation generates L-lactate ions
↓
L-lactic acid is excreted outside the cells along with protons
↓
As a result, malic acid in the must decreases, becoming mellow!
That is the flow of malolactic fermentation.
Of course, it goes through even more complex processes, but keep in mind that one of the objectives of malolactic fermentation is to achieve these kinds of effects.
Effects of Malolactic Fermentation
We have covered the mechanism of malolactic fermentation.
Next, let us look a little closer at the effects of malolactic fermentation.
Reducing Acidity
First, as mentioned earlier, there is the "deacidifying effect."
Because malic acid imparts a sharp acidity, an appropriate amount elevates wine quality, but too much makes the wine difficult to drink.
Basically, malolactic fermentation is not performed on white wine, but it appears to be adopted when aiming for a richer flavor or when acidity is high in cool-climate regions.
Impact on Aroma and Flavor
When wine undergoes malolactic fermentation, L-lactic acid increases in place of L-malic acid.
Things considered to be related are...
- Diacetyl... buttery, cheesy aroma
- Diacetyl... yogurt-like, buttery aroma
Therefore, malolactic fermentation is considered quite favorable for wine.
However, if it becomes too strong, it can turn into an unpleasant aroma (off-flavor), so selecting yeast and determining the duration according to the grape variety appear to be crucial.
Microbial Stability
For example, in the Champagne region, base wines undergo thorough malolactic fermentation. (Meaning complete removal of malic acid.)
Because malic acid serves as a nutrient source for numerous microorganisms, when conducting secondary fermentation in the bottle with long-term bottle aging, it is necessary to reduce the risk of contaminating microorganisms emerging.
In this way, there are cases where malolactic fermentation is performed in pursuit of microbial stability.
A Word on the Risks...
However, because malic acid is an acid that contributes to the pH of wine, the risk of malolactic fermentation raising the pH cannot be overlooked.
In particular, many grapes harvested in Japan have low acidity, so blindly applying malolactic fermentation causes the pH to rise too high, which is believed to lead to microbial contamination and a decline in wine quality due to high pH.
Incidentally, although we will not delve into it here, two patterns of malolactic fermentation exist: relying on natural origins, and using lactic acid bacteria starters.
Many producers of natural wine choose naturally derived fermentation, but because malolactic fermentation only occurs when the must has a certain pH value (somewhat high), risks are involved. (Such as microbial contamination.)
When producers put their wines through malolactic fermentation, it appears necessary to do so while taking various factors into account.
Knowing the Basics Helps You Understand the Conversation
When you want to hear various stories from wine professionals, you might not understand what they are saying unless you know some of the basics.
They may rarely discuss malolactic fermentation in detail, but conversations often proceed on the assumption that you already know it; knowing versus not knowing will also greatly change the way you perceive the taste of wine.
It might seem troublesome, but if you want to learn about wine, by all means try remembering the terminology, even if just the basics.
References
Malolactic Fermentation Trial Using Commercial Lactic Acid Bacteria Starters in Domestic Red Wine Production, Takumi Onda