These Two Words Are Key to Understanding Why Your Wine Tastes Buttery

The techniques used to produce a wine is made can offer enormous insight into its taste. Key terms like “whole cluster,” “carbonic maceration,” and “barrel aging” can inform you about a bottle’s flavor profile before you ever pull its cork. 

Of these, few terms cause as strong reactions in both wine professionals and casual drinkers as “malolactic fermentation.” So what exactly does this complicated-sounding phrase mean, and how does it affect what you’ll taste in your next bottle?

What is malolactic fermentation and what does it do?

“Malolactic fermentation (MLF) is a bacterial fermentation that converts malic acid to lactic acid, which is softer in mouthfeel,” says, Joel Burt, a California-based winemaker at Las Jaras Wines. 

Burt says that winemakers can choose to have their wines undergo the process. They can also block it, either partially or in total. “It really depends on the style of wine that the winemaker wants to achieve,” he says.

In addition to a softer mouthfeel, malolactic fermentation will raise the wine’s pH and lower its total acidity. It can make a wine feel creamier or more velvety on the palate. 

“In some wines, malolactic fermentation will add buttery flavors, depending on the strain and other factors,” says Burt. If a winery seeks to make a “big, buttery Chardonnay,” it can select a pure strain of lactic acid bacteria that produces large amounts of diacetyl, the chemical compound that creates buttery flavors in dairy products, popcorn, and wine. 

Malolactic fermentation’s ability to soften a wine’s mouthfeel can be particularly desirable in red wine vinification. 

“Winemakers pursue malolactic fermentation in red wines because it makes the wine have less astringency,” says Burt. 

With white wines, malolactic fermentation can offer stability and a creamier texture. 

Avoiding malolactic fermentation

Certain wines are favored without malolactic fermentation. 

“Avoiding malolactic fermentation can make the wine more angular and bright, which is preferred in some wines, like Sauvignon Blanc and Riesling,” says Burt. 

Malolactic fermentation is a naturally occurring process. So if it’s not desired, it will need to be blocked. The main ways to block malolactic fermentation include filtration, adding large doses of sulfur dioxide, or through the addition of an enzyme, lysozyme. 

Encouraging malolactic fermentation

Certain conditions can make malolactic fermentation difficult, such as cold cellars, high levels of alcohol, low pH, high sulfur, or high volatile acidity. When conditions are not ideal, Burt says that some winemakers add a bacterial strain to encourage malolactic fermentation. 

He says malolactic fermentation allows many wines to be bottled without sterile filtration, thanks to the increased microbial stability that the process provides. That’s advantageous for producers that prefer natural, low-intervention, and/or low-sulfur vinification. 

“At Las Jaras Wines, we do not block malolactic fermentation, as we tend to not filter our wines and we prefer less judicious use of sulfur,” says Burt.