Malolactic Fermentation

🔍 Quick Summary

Malolactic fermentation softens a wine’s sharp edges, trading green-apple bite for creamy roundness and buttery notes.

🛠️ What It Is

Malolactic fermentation (often called “MLF” or “malo”) is a secondary fermentation where tart malic acid the kind found in green apples is converted into softer lactic acid, the same kind found in yogurt or milk.

This transformation is carried out by lactic acid bacteria, primarily Oenococcus oeni, and typically occurs after the primary alcoholic fermentation has finished. It can happen naturally or be intentionally initiated by the winemaker through inoculation.

Although called a fermentation, no alcohol is produced. It’s more of a biological conversion that subtly reshapes a wine’s flavor, texture, and stability.

👅 Flavor & Style

Color

  • Minimal effect on color, though slightly more stable hues in reds due to increased pH.

Aromas & Flavors

  • Before MLF: Green apple, citrus

  • After MLF: Cream, butter, hazelnut, brioche (especially in whites)

  • Some wines also develop a faint dairy or lactic tang.

Structure

  • Acidity: Noticeably reduced — softer, rounder mouthfeel

  • Body: Enhanced creaminess and perceived fullness

  • Tannins: Slightly mellowed in red wines

Common examples:

  • Chardonnay from California or Burgundy, often buttery and rounded

  • Pinot Noir, especially in cooler climates, where MLF smooths acidity

  • Syrah/Shiraz, where partial MLF may be used to preserve brightness

🎯 Why Winemakers Use It

Winemakers employ malolactic fermentation to soften acidity, stabilize the wine, and add complexity.

  • Flavor effects – Adds buttery, creamy, or lactic notes; can mute overt fruitiness, creating a more layered wine

  • Structural impacts – Lowers total acidity, increasing roundness; adds mid-palate weight and texture

  • Technique variation –

    • Whites: Winemakers may block MLF to preserve zippy acidity (e.g., in Riesling or Sauvignon Blanc)

    • Reds: Often used universally for stability and softness

    • Can be done in barrel (for richness) or tank (for freshness)

Tradeoffs:

  • Too much MLF can flatten a wine’s brightness or mask varietal character

  • Requires careful microbial management to avoid spoilage

  • Adds time and cost to the winemaking process

🔗 Related Topics to Explore

  • 🍇 Chardonnay – A grape deeply shaped by malolactic decisions

  • 🧪 Yeast in Winemaking – Primary fermentation's microbial partner

  • 🧂 Sur Lie Aging – Enhances the creamy effects of MLF

  • 🧵 Barrel Fermentation – Often paired with MLF in whites

  • ❄️ Cold Stabilization – Another post-fermentation step

🤓 Deep Dive Topics

  • Malolactic Fermentation – Wikipedia

  • Yeast in Winemaking – Wikipedia

  • Wine Acidity – Wikipedia

  • Winemaking – Wikipedia

  • Wine Chemistry – Wikipedia