What is Malolactic Fermentation?

Question from Sally: I was at a tasting room at a winery and when the guy at the bar served the Chardonnay he said “40% M L”. I was too intimidated to ask what that means.

Reply: Hello, servers and barristas everywhere – stuff like this is what steers people toward beer! Be helpful and kind to your customers or get a new job description!

OK, I’ve stepped down from the soap box…

ML is short for malolactic fermentation. This normally follows the primary, alcoholic fermentation so sometimes it’s called the second fermentation. It’s actually a conversion, but whatever.

It’s routine for reds, for the sake of stability and to soften the acid. When it comes to whites, it’s more of a question mark and when people talk about ML it’s usually in reference Chardonnay. This is the technique that makes your Chardonnay buttery. Here’s how it goes:

It takes the wine maker about three weeks to make his Chardonnay. Then, lactic-acid bacteria is added to the new wine. It causes the tart malic acid – the green apple acid, to convert to soft lactic acid – the milk acid. So the wine feels softer on your palate.  ML also has a byproduct, called diacetyl, which adds a sort of viscous, oily sensation to the texture and smells and tastes buttery.

The wine maker might choose to go with ML to reduce the acidity or because he wants the buttery character or both. Depending upon his stylistic goals he can do ML for only some of the wine and blend it with non-ML wine. It’s a question of how high the acid is, to begin with, and how much of it is malic – where’s the wine maker going to be in terms of acid when it’s all over? It’s especially important for whites to be nice a crisp.

And, it’s a question of stylistic preference. Some wine makers love the buttery character and think of it as a complement to the wine. Others might call it a competition. In cool climates, where the acid is sometimes painfully high to begin with, ML is routine.

When the server says it’s 40% ML, what he’s saying is that the wine maker decided on a compromise. If he made 10 barrels of Chardonnay, 4 of them were put through ML. He’ll blend that wine with the non-ML wine to reach a nice balance of fruit to buttery character and a sound acidity.  

Trivia du Jour: Diacetyl is the substance they add to microwave popcorn to make it buttery!

Getting back on my soap box, those who really know wine understand that there’s waaaay to much to know – nobody knows it all – which should give them empathy for those just getting started. They should never make someone feel bad or ignorant when they have questions!

I hope that helps! And, please don’t hesitate to let me know when I’ve used jargon that’s confusing! Cheers!

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