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Controlling Wine Acidity With A Malolactic Fermenation

Malolactic CultureMy Cabernet Franc and Carmenere, made from juice, both need to have their acid levels increased. Both 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 malolactic fermentation?

Name: Dennis D.
State: Ohio

Hello Dennis,

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

  • To Make The Wine Stable: If the wine is forced through an MLF before bottling, you don't have to worry about an MLF occurring in the bottles. Having an MLF in the wine bottle would be the last thing you'd want.
     
  • To Lower The Acid: If the wine's acidity level 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: Wines that go through an MLF are lowering their malic acid content and raising their 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 an 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.

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.

With that being 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. I bring this up simply to point out the fact that if you do add malic acid back to the wine, it is also very important that the wine be treated with sulfites, such as sodium metabisulfite. This is needed to destroy the culture you added, 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 went on during the MLF besides just an exchange of acid that altered the flavor of the wine, as well. One 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.

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 malo-lactic 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 malolactic fermentations — why they are used, how they affect a wine — there's a great article on our website about it that may be of interest: Malolacitc Fermentation: Is It Right For You And Your Wines?

Happy Winemaking,
Ed Kraus
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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.

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