Wine Word Wednesday: Malolactic Fermentation

Photo Credit: Robert S. Donovan's flickr

Ever wonder what gives some wines a buttery taste? Some mistakenly say it's from oak, but really it's from a process called malolactic fermentation. The name is somewhat misleading as it isn't really a fermentation at all. Rather, malolactic fermentation (or MLF) is the conversion of harsh malic acid into the softer lactic acid. Lactic acid bacteria is either present in the wine or a cultured version is added. It always happens after regular fermentation, if it happens at all.

This is an important step to take in the practice of wine making because it can control how well balanced the wine is. It is a step that is universally taken in red wines, especially in those from cooler regions where acid levels would be out of balance with the sweetness levels. However, it is used far more judiciously in white wines where high levels of acid are needed to balance out sugar levels and where preservation of the delicate grape flavors is desired. You'll never see it in a Riesling, for example, or in Sauvignon Blanc.

Chardonnay is an exception to this rule (and in wine there is always an exception). Chardonnay is a very neutral grape and seems to have an affinity for the creamier flavors that MLF produces. Just try a California Chardonnay or a White Burgundy and compare that to Chardonnay from Chablis. You'll notice a very distinct difference in the levels of acid and the flavors. Steely for Chablis, creamy for California Chardonnay and White Burgundy. (Or just read yesterday's post).

So where does butter come in? If MLF gets out of control, it will reduce acid too far and produce excessive amounts of diacetyl. At low levels, it is perceived as toasty or nutty, but at high levels it produces buttery flavors that can be unpleasant in wine. Interestingly, levels of diacetyl are much more easy to detect in white wines than in red wines. Fortunately, new world winemakers have become much more cautious with MLF and that super buttery California Chardonnay should be a thing of the past.

Cheers.
Sandy