Wine Words Demystified: Malolactic Fermentation

You know the deal, the more some folks learn about a topic, the more shortcuts/slang/acronyms/initials/technical jargon can be tossed around.  I’m here to help you understand those sometimes mysterious words and phrases, thus – Wine Words Demystified!

This week’s word/phrase is Malolactic Fermentation

According to Karen MacNeil‘s The Wine Bible:

This process has nothing to do with regular FERMENTATION since it does not involve yeasts or the production of ALCOHOL.  Rather, malolactic fermentation is a chemical conversion of ACID instigated by beneficial bacteria.  During the process, the strident sharp malic acid in grapes is converted to softer lactic acid.  This has the effect of softening the overall impression of acid when the wine is drunk. Malolactic fermentation may also contribute a buttery character to the wine and may add complexity…Malolactic fermentation can either occur naturally or be prompted by the winemaker.  All red wines go through malolactic fermentation.  White wines may or may not. 

In other words malolactic fermentation, also referred to as “ML”, or “MLF”,  is a conversion of malic acid, which is naturally present in grapes, via a beneficial bacteria (Oenococcus oeni, and others, including the stuff in yogurt and milk, Lactobacillus) to lactic acid.

Ball-and-stick model of L -lactic acid
Ball-and-stick model of L -lactic acid (Photo credit: Wikipedia)

I’ve heard “ML’ most often used when discussing Chardonnay.  That’s because Chardonnay is the wine with the biggest reputation for being “buttery”.  That buttery mouthfeel, aroma and flavor is a due to the presence of diacetyl, which is byproduct of the process.  Diacetyl is one of the compounds that gives butter its characteristic taste.  And that’s how Chardonnay that has undergone “ML” (and that folks either love or hate) comes to be described as “buttery”!


  1. We just saw (or should I say tasted) the results of this on our recent visit to Burgundy…Buttery is great!

    1. Martin D. Redmond says:

      I really enjoy the mouthfeel of white wines that have undergone malolactic fermentation too!

      1. Yesterday, I had a 2007 Puligny Montrachet, La Garenne, 1ere Cru…..Was awesome…and what timing :)

      2. Martin D. Redmond says:

        Wow! That sounds great! I drink a LOT of wine, but I’d never had a Chablis until last week! A good one too – ’08 Domaine Drouhin Vaudon Chablis Grand Cru Les Clos. Won’t be my last Chablis…loved it!

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