What is Malolactic Fermentation? The Buttery Taste in Wine


February 20, 2017 Blog » Learn About Wine » What is Malolactic Fermentation? The Buttery Taste in Wine

Ever wondered why some wines have a creamy or buttery taste? The process of Malolactic Fermentation is a winemaking process that gives both red and white wines a richer and creamier texture. Oddly enough, Malolactic Fermentation isn’t technically a fermentation at all.

What is Malolactic Fermentation?

Malolactic Fermentation Oenococcus Oeni Illustration
Bacteria is responsible for releasing an impact compound called Diacetyl which gives wine buttery/creamy aromas.

Also called malo or MLF, malolactic fermentation is a process where tart malic acid in wine is converted to softer, creamier lactic acid (the same acid found in milk). The process reduces acidity in wine and also releases some carbon dioxide in the meantime.

MLF isn’t technically a fermentation because it doesn’t use yeast. Instead, a special kind of bacteria called Oenoccocus Oeni (along with a few other Lactobacillus strains) eat the malic acid in wine and poop out lactic acid. Yum! The result is a wine with a creamy, almost oil-like texture on the middle of your tongue, that adds a marvelous, velvety texture to the wine. Thank you, lil’ guys!

What Wines Undergo Malolactic Fermentation?

Nearly all red wines and some white wines (such as Chardonnay and Viognier) undergo malolactic fermentation.

One way to recognize MLF in a wine is to note if it has a creamy, oily mid-palate texture. This can indicate malo (or also lees aging). Another easy way to identify the malo is to see if the wine was aged in oak, since MLF typically occurs while wines age in oak barrels. It’s not uncommon for white wines to let only a small percentage of the wine have the malolactic conversion. This is a clever way of adding texture and body to the wine without losing too much of the positive floral and citrus aromas that waft off when white wines are aged in oak.

GMO Yeasts and Bacteria in Wine

Wine grapes are not genetically modified. However, to date there are both yeast strains and bacteria that have been genetically modified to help fermentations complete (and produce desirable aromas in wine). Oenoccocus oeni is one of the bacteria strains that is has been genetically modified, but to our knowledge there are no GMO strains on the market.

What’s our take on this slippery topic? It’s tricky. On one hand, GM yeasts and bacterias could produce better, more consistent wines that are more affordable. On the other hand, they could remove the sense of terroir in wine, which has been shown more recently to be greatly affected by regional bacteria and yeast diversity.


Additional Reading
If you want to read more about GMOs in wine, Wine Anorak pretty well sums it up here.

For the longest time, people were concerned that O. oeni caused an increase of histamines in wine (a health concern). Oenococcus Oeni vs. Histamines. This study clarifies that it’s not true.

Here’s a neat study that discusses the chemical changes that occur with MLF in Oregon Chardonnay and Pinot Noir Roles of yeast and lactic acid bacteria in malolactic fermentation of wines : a chemical and sensory study


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By Madeline Puckette
I'm a certified sommelier and creator of the NYT Bestseller, Wine Folly: The Essential Guide to Wine. Find me out there in the wine world @WineFolly