What is malolactic fermentation in winemaking?
The techniques used to make a wine can offer profound insight into its flavor. Key terms such as "whole cluster," "carbonic maceration," and "barrel aging" can provide information about a bottle's flavor profile even before it's opened.
Of these terms, few evoke such strong reactions from both wine professionals and wine enthusiasts as "malolactic fermentation." So, what exactly does this complex-sounding phrase mean, and how does it affect the flavor of your next bottle?
What is malolactic fermentation and what is it used for?
“Malolactic fermentation (MLF) is a bacterial fermentation that converts malic acid into lactic acid, which provides a smoother mouthfeel,” says Joel Burt, Californian winemaker at Las Jaras Wines.
Burt explains that winemakers can choose to have their wines undergo this process. They can also block it, either partially or completely. “It really depends on the style of wine the winemaker wants to achieve,” he explains. In addition to a smoother mouthfeel, malolactic fermentation raises the wine’s pH and reduces its overall acidity. It can make a wine feel creamier or velvetier on the palate.
“In some wines, malolactic fermentation contributes buttery flavors, depending on the strain and other factors,” Burt explains. If a winery is looking to produce a powerful, buttery Chardonnay, it might select a pure strain of lactic acid bacteria that produce large amounts of diacetyl, the chemical compound that creates buttery flavors in dairy products, popcorn, and wine.
The ability of malolactic fermentation to soften a wine's mouthfeel can be especially desirable in red winemaking. "Winemakers look for malolactic fermentation in red wines because it reduces the wine's astringency," says Burt.
In white wines, malolactic fermentation can offer stability and a creamier texture.
Prevent malolactic fermentation
Certain wines are preferred without malolactic fermentation. “Avoiding malolactic fermentation can make the wine more angular and bright, which is preferred in some wines, such as Sauvignon Blanc and Riesling,” says Burt.
Malolactic fermentation is a natural process. Therefore, if it is not desired, it will be necessary to stop it. The main ways to stop malolactic fermentation include filtration, the addition of large doses of sulfur dioxide, or the addition of an enzyme, lysozyme.
Promote malolactic fermentation
Certain conditions can hinder malolactic fermentation, such as cold cellars, high alcohol levels, low pH, high sulfur content, or high volatile acidity. When conditions are less than ideal, Burt notes that some winemakers add a bacterial strain to stimulate malolactic fermentation.
He adds that malolactic fermentation allows many wines to be bottled without sterile filtration, thanks to the greater microbial stability the process provides. This is advantageous for producers who prefer natural, low-intervention, or low-sulfur winemaking.
“At Las Jaras Wines, we don’t block malolactic fermentation, as we usually don’t filter our wines and prefer a less prudent use of sulfur,” says Burt.
