Malolactic fermentation

Malolactic Fermentation

Malolactic fermentation spotting on a wine sample.

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, and is a key step in the production of many wines, particularly red wines and some white wines such as Chardonnay.

History

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Hermann Müller, a pioneer in the study of malolactic fermentation.

The understanding of malolactic fermentation has evolved over time. It was first observed in the early 20th century, with significant contributions from scientists such as Hermann Müller who studied the microbiological aspects of winemaking. The process was initially considered a fault, but later recognized as beneficial for the stability and flavor profile of wines.

Process

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Diagram of the malolactic fermentation process.

Malolactic fermentation is initiated by the inoculation of wine with lactic acid bacteria. These bacteria convert malic acid into lactic acid and carbon dioxide. The reduction in acidity results in a smoother, rounder mouthfeel and can enhance the complexity of the wine's flavor profile.

Bacteria Involved

Oenococcus oeni, the primary bacterium responsible for malolactic fermentation.

The primary bacterium responsible for malolactic fermentation is Oenococcus oeni. Other bacteria such as Lactobacillus and Pediococcus can also perform MLF, but O. oeni is preferred due to its ability to thrive in the acidic and alcoholic environment of wine.

Impact on Wine

Malolactic fermentation can significantly alter the sensory characteristics of wine. It reduces acidity, enhances body, and can impart buttery flavors due to the production of diacetyl. This is particularly desirable in Chardonnay wines.

Chardonnay grapes, often subjected to malolactic fermentation.

Techniques

Winemakers can control malolactic fermentation through various techniques, including the use of commercial bacterial cultures, temperature control, and nutrient management.

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Inoculation and nutrient management for malolactic fermentation.

Challenges

While malolactic fermentation offers many benefits, it also presents challenges. Uncontrolled MLF can lead to spoilage and off-flavors. Winemakers must carefully manage the process to ensure desired outcomes.

Lactobacillus bulgaricus, another bacterium that can perform MLF.

Chemical Reactions

The primary chemical reaction in malolactic fermentation is the decarboxylation of malic acid to lactic acid and carbon dioxide. This reaction is catalyzed by the malolactic enzyme.

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Chemical structure of acrolein, a compound that can be produced during MLF.

Related Pages

• Winemaking
• Fermentation
• Lactic acid bacteria
• Chardonnay