Malo-Lactic Fermentation is an important process to understand because it has a profound effect on the taste and texture of finished wine. Once you know whether or not a wine has under gone Malo-Lactic fermentation you will have a better idea of its qualities, including aromas, flavors and body.

First of all, the name Malo-Lactic fermentation (MLF) is a misnomer. Unlike the primary Alcoholic fermentation, which is carried out by yeast (a single cell fungus), Malo-Lactic is done by lactic acid bacteria. The Malo-Lactic process changes all of the tart tasting Malic acid naturally present in the grape into Lactic acid. Malic acid is found in granny smith apples and Latic acid is found in milk products, so you can imagine those very different flavors and see that this process has a huge effect on the wine.

Almost all red wines go through this process because the tart Malic acid is too harsh for red wines -- it would be too tart to be palatable. So it is really in the White wine arena where MLF plays a more important role. Almost all of the crisp and clean Sauvignon Blancs, Rieslings and Pinot Grigios do not go through MLF because they need that Malic acid to balance the dense fruit aromas and flavors, and because they are intended to have pleasant levels of tart flavor. Chardonnays are a completely different story.

The Chardonnay grape is a bit of a chameleon -- it takes on many different qualities depending on how it is made, where it is from and how it is aged before bottling. MLF plays an important role on determining the final flavor profile of the wine. Wines that are 100% ML fermented have a pronounced creaminess and a richer body, most stereotypically found in California Chardonnay, but also present in other New World Chards and some French white Burgundies. Chardonnays that are not ML fermented are crisper with notes of green and red apple and more medium to light bodied. This is the style of some of the un-oaked Chards on the market and the style of most of the still wine that will then be used for Champagne or other Chard based sparkling wines.

A large percentage of what is on the market now is a blend of wines that have and have not undergone MLF. The winemaker will use all of his or her experience to decide what ratio of ML fermented wine to non-ML fermented wine should be in the final blend. This is one of the factors that accounts for the huge variation found in Chardonnay, for example.

Hopefully this has answered some of the question regarding MLF, and the next time you see MLF in a tasting note or wine magazine it will be more useful to your understanding of that wine.