Malolactic fermentation (MLF or “malo”) is a secondary wine-making process in which lactic acid bacteria convert sharper malic acid into softer lactic acid and carbon dioxide. It usually reduces perceived acidity and can change the wine’s texture and aroma. Despite the name, it is not a yeast fermentation that produces alcohol.
MLF can soften a wine’s acidity, improve microbial stability when completed and contribute texture or flavour complexity. Some wines develop buttery, creamy or dairy-like notes, especially when MLF is combined with certain lees and oak practices. Those aromas are not produced in every wine that undergoes MLF.
Most red wines undergo malolactic fermentation, although practices vary. For white wines, it is a stylistic decision: some Chardonnay producers encourage MLF for a rounder texture, while producers seeking a crisp, high-acid style may block or prevent it.
Winemakers manage temperature, sulphur dioxide, pH, bacterial activity and cellar hygiene to encourage or prevent MLF. The process may occur after alcoholic fermentation or, in some cases, concurrently.
Chef’s pairing tip: A Chardonnay that has undergone MLF may show a softer texture that pairs well with richer fish, poultry, cream sauces and browned butter. Taste the wine; not every MLF Chardonnay is buttery.
Key distinction: Malolactic fermentation converts malic acid to lactic acid; alcoholic fermentation converts sugar to ethanol and carbon dioxide.
This term is one of hundreds covered in depth across OCS courses, learning paths, and 1-on-1 coaching with Chef Eric.
