Malolactic Fermentation and Wine

Wine Fermentation. Morsa Images / Digital Vision / Getty Images

Malolactic fermentation is a vital part of the vinification process for the vast majority of red wines and a handful of white wines. Malolactic fermentation (also known simply as "malo" or MLF)  is largely associated with Chardonnay and is one of the key reasons that Chardonnay can exhibit a buttery component on the nose and palate. Typically tough to initiate with high acid grapes, the low-level acidity of most Chardonnay makes it a natural choice to run through malo.

What is Malolactic Fermentation?

Basically, malolactic fermentation is a secondary fermentation that requires hardworking bacteria and instead of yeast. Essentially, it is the process of taking the harsher malic acid that occurs naturally in the wine must and converting it to a softer lactic acid. Malic acid is associated with the tart acid found in a Granny Smith apple, while lactic acid is the more subtle acid found in milk, butter, cheese and yogurt (and it is the diacetyl derivative of the lactic acid, that shows up as "buttery" in a Chardonnay that has undergone malolactic fermentation). By converting malic acid to lactic acid via Lactobacillus bacteria, you end up with a wine that carries a lower total acidity and is generally more approachable, often creamy in texture and less abrasive on the palate.

Why Use Malolactic Fermentation?

While malolactic fermentation often happens naturally during the fermentation process, winemakers can pre-determine whether to allow it to happen or prevent it based on the stylistic results they are shooting for in the bottle.

While a wine that has undergone malolactic fermentation is less acidic in nature, the trade-off is that it will often have diminished fruit character. Today, many Chardonnay producers are putting part of the blend through malolactic fermentation and holding a percentage of the base wine back to maintain the purity of fruit.

Once malo is complete, they blend both batches together to retain the fruit character, while keeping the overall acidity in check. This split production method has replaced the somewhat popular "all or nothing" approach that has plagued many Chardonnay wines, which have taken a bit of a beating for being "over manipulated," over processed and drowned in malo. As a happy medium, partial malo has been a successful compromise in many popular Chardonnays where the malic acid lends complexity and the non-malolactic wine contributes solid fruit.

What Does Malo Taste Like?

Malolactic fermentation results in a wine that is overall more approachable on the palate due to it's lower levels of acid, softer textures, rounder profiles and increased aromatic intensity and integration of fruit and oak in a wine. It's typically the fuller-bodied white wines and fuller bodied red wines that benefit the most from a run through malolactic fermentation.