Malolactic fermentation

A process in winemaking that converts malic acid to lactic acid

Malolactic fermentation (MLF) is a process in winemaking where tart-tasting malic acid, naturally present in grape must, is converted to softer-tasting lactic acid. This process is carried out by lactic acid bacteria, primarily Oenococcus oeni, although other species such as Lactobacillus and Pediococcus can also be involved.

Process

Malolactic fermentation typically occurs after the primary alcoholic fermentation, although it can sometimes occur simultaneously. The process involves the decarboxylation of L-malic acid to L-lactic acid and carbon dioxide. This conversion reduces the acidity of the wine and can contribute to a smoother, rounder mouthfeel.

File:Malolactic fermentation diagram.png

Diagram of malolactic fermentation process

The reaction can be summarized as follows:

C_H_O_ (malic acid) _ C_H_O_ (lactic acid) + CO_ (carbon dioxide)

Role in Winemaking

Malolactic fermentation is a crucial step in the production of many wines, particularly red wines and some white wines such as Chardonnay. It can influence the flavor profile of the wine, adding complexity and buttery notes due to the production of diacetyl, a byproduct of the process.

Benefits

• Acidity Reduction: MLF reduces the acidity of the wine, making it more palatable and balanced.
• Flavor Complexity: The process can introduce new flavors and aromas, such as buttery or creamy notes.
• Microbial Stability: By converting malic acid to lactic acid, MLF can help stabilize the wine and prevent spoilage by other microorganisms.

Challenges

• Control: Winemakers must carefully control the process to avoid excessive diacetyl production, which can lead to undesirable buttery flavors.
• Timing: The timing of MLF is critical; if it occurs too early or too late, it can affect the quality of the wine.

Techniques

Winemakers can encourage malolactic fermentation by inoculating the wine with specific strains of lactic acid bacteria. Alternatively, they may allow it to occur naturally, relying on indigenous bacteria present in the winery environment.

Inoculation

Inoculation involves adding a cultured strain of Oenococcus oeni to the wine. This method provides more control over the process and can ensure a consistent outcome.

Natural Fermentation

Allowing MLF to occur naturally can result in more complex flavors, but it carries the risk of unpredictable results and potential spoilage.

Impact on Wine Styles

Malolactic fermentation is more common in red wines, where it is almost universally practiced. In white wines, the decision to undergo MLF depends on the desired style. For example, Chardonnay often undergoes MLF to achieve a rich, buttery flavor, while other white wines may avoid it to preserve crisp acidity.

Related pages

• Winemaking
• Fermentation (wine)
• Lactic acid bacteria
• Chardonnay