Malolactic fermentation (or ML) is a secondary fermentation driven by lactic acid bacteria, converting harsh malic acid into softer lactic acid and carbon dioxide. This biochemical process reduces acidity and adds complexity, round texture, and butter or cream notes to wine. It occurs naturally or under winemaker control after the primary yeast fermentation. While essential in red winemaking and Burgundy whites, winemakers may block ML in crisp white wines to preserve bright acidity, making it a key stylistic choice.
WHY IT MATTERS FOR COLLECTORS
Collectors should understand that malolactic fermentation is central to red wine texture and ageing potential. Wines that undergo full ML age differently than those with blocked ML, affecting how they cellar and when to drink.
Tasting cues
- MLF softens sharp malic (green-apple) acid into creamier lactic acid.
- Buttery or creamy notes often come with diacetyl from certain MLF regimes (especially oak-aged Chardonnay).
- Reds almost always complete MLF; whites are a stylistic choice.
Examples
- California and Burgundy barrel-fermented Chardonnay frequently undergo full MLF.
- Many German Rieslings and Loire Sauvignons block MLF to keep a crisp line.
- “Unfiltered, full MLF” on a red is normal cellar talk, not a defect.
Cellar actions
- Match MLF style to food: creamy Chardonnay with rich fish; non-MLF whites with bright seafood.
- Do not confuse MLF creaminess with residual sugar sweetness.
Related terms
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