Understanding the Effects of a Malolactic Fermentation in Wine

Wines Going Through Malolactic FermentationMy Cabernet Franc and Carmenere, made from juice, both need to have their acid levels increased. Both wines went through malolactic fermentation. What type of acid is best to use? I have acid blend but it contains malic acid. Would using malic acid defeat the purpose of the malolactic fermentation in this wine?

Name: Dennis D.
State: Ohio
Hello Dennis,

There are three main reasons for wanting a malolactic fermentation in wine (MLF):

  • To Make The Wine Stable: If the wine is induced into an MLF before bottling, you don’t have to worry about an MLF occurring in the wine bottles, spontaneously. Having a malolactic fermentation in the wine, naturally, while it’s in the wine bottle would be the last thing you’d want.
  • To Lower The Acid Of The Wine: If the wine’s acidity is too high and the wine is tasting too sharp or too tart, then a malolactic fermentation can very possibly improve the wine by lowing its acidity level.
  • To Change The Flavor: A malolactic fermentation in wine lowers the malic acid content and raises the lactic acid content. The net result is a lowering of the wine’s overall acid level, but also, because of the exchange of malic to lactic acid, the wine takes on a different flavor character. The wine will tend to be less fruity and more earthy. This may, or may not, be an improvement depending on the wine and your personal taste preference.

If your malolactic fermentation caused the wine to be too low in acid, I am going to assume that you did not put the wine through the MLF to lower its acidity level, but rather, you did it to either make the wine more stable or to change its flavor profile.Shop Malolactic Culture

With that said, if you add malic acid back to the wine you are increasing its potential to become unstable again, especially sense, I assume, you put a malolactic culture in the wine to initiate the MLF. The malolactic culture is a bacteria that consumes malic acid. If you add more malic acid to raise the acidity of the wine, you could be feeding a renewed MLF.

This is why it is very important that the wine be treated with sulfites, such as sodium metabisulfite. This is needed to destroy the bacteria culture, or your MLF will very likely start back up again–fueled by the new malic acid.

If you put the wine through a malolactic fermentation for reasons of flavor, then again, adding malic acid is going to be counterproductive. The harsher malic acid was fermented into half carbon dioxide gas and half lactic acid. The lactic acid is not as harsh as malic. So if you replace your acid deficiency with malic acid you are going to go backwards.

There are some other things that go on with a malolactic fermentation in wine. It’s not just an exchange of acid that’s altering the wine’s character. One major example, is the production of diacetyl. This is a substance that causes the wine to have a buttery flavor and aroma and can give the wine a more creamy texture. These effects are there to stay regardless if you add back malic acid or not. So there could be an argument for using malic acid to raise the acid level if all you where looking for was the diacetyl effect on the wine.Shop Acid Test Kit

After going through all of this, I think it starts to becomes clear that, for the most part, adding malic acid back to a wine that just went through a malolactic fermentation, does not make too much sense. You are better off using a blend of tartaric acid and citric acid, instead. I would suggest 2 parts citric acid and 1 part tartaric acid.

If you would like to read more about using a malolactic fermentation in wine—why they are used, how they affect a wine—you might want to take a look at: Malolactic Fermentation: Is It Right For You And Your Wines?

Happy Winemaking,
Ed Kraus
Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

2 thoughts on “Understanding the Effects of a Malolactic Fermentation in Wine

  1. My friend transferred our kit wine into carboy and messed up by adding campden tablets after 1 week of fermentation. Thus killing the fermentation. How do we restart fermentation or did we ruin it.

    • Ty, you may not need to do anything.

      If you used an actual packet of “wine” yeast, it may continue to ferment on its own. Wine yeast is somewhat resistant to sulfites such as Campden tablets.

      The fermentation could also be already finished. You can check this with a hydrometer. If it gives a Specific Gravity reading of .998 or less, the fermentation is done, and you have no worries.

      If the fermentation does not continue on on its own and the hydrometer is reading a higher number than .998 [for example 1.020] then you will need to restart the fermentation.

      You start by making a yeast starter. This can be done by taking a quart mason jar; fill it half way with the wine in question, then add water until it is about 2/3 full. Next, add a 1/4 teaspoon of yeast nutrient, or better yet, a 1/2 teaspoon of Yeast Energizer, it you got it.

      Now sprinkle a whole packet of wine yeast onto it. Secure a paper towel over the top with a rubber band and allow to sit for a day in some place that isn’t cold.

      You should see some foaming on top after a day. Now you can pour this starter into your batch of wine, and you should see the fermentation take off in a day or two.

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