Adding Malolactic Bacteria to Wine

If you’ve been trying to figure out the proper process for adding malolactic bacteria to wine, you’ve come to the right place. It helps to understand the entire process so you can figure out your place in it, if you have any place at all. What do we mean by that? You’ll see.

What Is Malic Acid?

Malic acid is a naturally occurring chemical compound found in most fruits. It is what makes unripe green apples so tart, and in fact the name comes from the Latin word “malum” for apple.

You get hints of it in pretty much any unripe fruit, and in many ripe fruits as well.

Of course, it is present in almost all ripe, sweet wine grapes.

What Is Malolactic Fermentation?

Malolactic fermentation is not actually fermentation at all, because there is no yeast involved or required, but rather decarboxylation, a conversion process. But chemists have long called the process of MLF fermentation because of the release of gases.

Instead, what happens when wine is made is that grapes are crushed and left out to ferment.

At this point, all the local yeast and bacterial cells are going to compete to consume this sugary substance.

In almost every case, yeast will win. It is a more complex organism and has perfected its rapid fermentation process over hundreds of thousands, if not millions, of years.

Maybe billions.

Thus, the yeast crowds out all the competition and consumes all the sugar in the grape juice, or must. It will then release alcohol and carbon dioxide as waste products. Lucky us.

At this point, primary fermentation is complete, and many people will be perfectly content to simply consume this beverage as wine.

However, if you leave this wine out for a bit longer, you will get an even smoother, creamier product.


Well, now that yeast is done fighting the competition, but alcohol has been created to fight off any nasty invaders, beneficial bacterial cells are free to do their thing.

The bacterial cells are called Oenococcus oeni, and they are part of the family of lactic acid bacteria. They are only interested in consuming the malic acid in the must, which the yeast left alone because it is not sugar.

Now, the bacteria consume the malic acid and convert it to lactic acid, just like the acid produced in dairy, giving wine a smooth, creamy flavor and texture that often comes with notes of butter and vanilla.

You’ll find this process takes place naturally in all red wines and in many white wines as well.

How Do You Add MLF to Wine?

If you’re hoping to mimic this process, you can try it one of two ways.

You can of course follow the examples of our ancestors in winemaking and allow malolactic fermentation to take place as a natural course of winemaking.

Once primary fermentation has completed, the necessary bacteria will find its way into your must and begin the process.

However, modern times often call for modern approaches, and you may be interested in maintaining more control. This modern approach can be useful for a couple of reasons.

First, if you decide to wait, malolactic fermentation may not take place until after your wine is bottled, which can create unwanted gases that can cause the bottles to explode.

Second, it can help speed up the secondary fermentation process, which can otherwise take weeks or even months to complete.

To add your own malolactic bacteria to wine, you can simply purchase the correct strain from a reputable source and, in general, add one pack for every 5 to 10 gallons of wine.

In the end, making great wine is all about striking the right balance between letting nature take its course and helping nature along.

Make sure you’re allowing yourself to bend and stretch according to where you’re at in your own process, taking note of where you’ve failed and how you’ve succeeded, and then make corrections as you see fit.

Over time, you’ll find yourself a master of your craft.


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