What Is Malolactic Fermentation? Wine’s Game Changer

Editor: Arshita Tiwari on Jun 30,2025

You know that creamy texture in some Chardonnays or the soft, round finish in a bold red? That’s not just the grape doing its job. That’s malolactic fermentation quietly working in the background.

It’s not the kind of thing you’ll find on the front label of a wine bottle, but it’s one of the winemaker’s sharpest tools. Subtle. Technical. And when done right, absolutely game-changing.

Let’s break it down—no fluff, no textbook language—just what malolactic fermentation in wine really means, how it works, and why it plays such a crucial role in the final pour.

First Off—What Is Malolactic Fermentation?

Forget everything you associate with the word "fermentation" for a moment. Malolactic fermentation (or MLF if you want to sound like a cellar pro) isn’t about converting sugar to alcohol. It's a secondary process that kicks in after primary fermentation is done.

Here’s the short version:
It converts malic acid—the same stuff that makes green apples tart—into lactic acid, the smoother acid you’d find in yogurt or milk. So, instead of a sharp, punchy acidity, the wine gets a rounder, creamier mouthfeel.

And no, it’s not yeast doing the job this time. It’s lactic acid bacteria, most commonly Oenococcus oeni, stepping in and doing the conversion.

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Why Winemakers Use It (And Why It Works)

MLF isn’t something you throw into every wine like salt in pasta water. It’s used with purpose. It softens, stabilizes, and subtly shifts the wine’s personality. When a winemaker wants a smoother finish or a more integrated flavor profile, malolactic fermentation is the go-to move.

Let’s spell out what it brings to the table:

• It tames high acidity. Especially in cooler-climate wines or grapes picked early, malic acid can be sharp. MLF mellows that edge.
• It adds texture. You’ll feel it more than you’ll taste it—creamy, silky, often with a bit more weight.
• It introduces subtle flavors. Diacetyl, a natural byproduct of this process, gives off buttery, nutty, or brioche-like notes (not always, but often).
• It stabilizes the wine. Doing MLF under a winemaker’s watch means no surprises in the bottle later.

How Malolactic Fermentation Works (Without the Science Jargon)

If you're here for a PhD-level explanation, you're in the wrong cellar. But if you want to understand the core of what is malolactic fermentation, here it is in plain language:

Malic acid has two acid groups, which makes it tangy and mouth-puckering. Lactic acid? Just one acid group. That swap makes the wine smoother, rounder, and easier to drink.

The process also releases a bit of carbon dioxide, but not enough to make your wine fizzy. It’s quiet, it’s slow, and if you weren’t looking for it—you’d miss it happening.

Wines That Typically Go Through MLF

Let’s get one thing clear: malolactic fermentation in wine isn’t automatic. It’s a winemaking decision. Some wines absolutely benefit from it. Others? Not so much.

Reds

Almost every red wine you’ve had—Merlot, Syrah, Cabernet, Pinot Noir—has gone through MLF. Reds usually need it. It helps balance tannins and soften the overall mouthfeel without stripping away character.

Whites

Here’s where the fork in the road appears.

• Chardonnay? Often yes, especially if the winemaker’s going for that creamy, oaked style.
• Riesling, Sauvignon Blanc, Albariño? Usually no. These wines live and die by their bright acidity, and MLF would mute that.

There’s also the blended approach: partial MLF or blending MLF-treated wine with unoaked, acidic wine to get the best of both worlds.

What It Actually Tastes Like

You can’t always "taste" malolactic fermentation, but its impact is there. The wine feels softer. The acidity seems less aggressive. In some cases, there’s that unmistakable buttery or creamy note—especially in wines aged in oak.

But here’s the thing: not all MLF wines taste buttery. That depends on how much diacetyl (the butter compound) sticks around. Some winemakers stir the lees to reduce it. Some use stainless steel tanks to avoid it entirely.

So, if you’re sipping a white that feels silky and rich, or a red that glides across your tongue without biting—chances are, malolactic fermentation had a hand in that.

MLF vs. Alcoholic Fermentation—They’re Not the Same

Let’s not confuse the two. They’re both called “fermentations,” but they serve totally different roles:

One gives wine its kick. The other gives it finesse.

Can Winemakers Control It? Definitely.

MLF isn’t something winemakers leave to chance—at least not anymore. Whether they want it to happen or avoid it altogether, they’ve got tools:

• Inoculation: Want MLF? Add selected strains of Oenococcus oeni to get predictable results.
• Temperature control: MLF likes it warm. Keep the cellar too cool and it’ll stall.
• Sulfite additions: Sulfur dioxide (SO?) can halt MLF. Want to preserve the crispness? Hit the wine with sulfites.
• Sterile filtration: To make sure it never happens, especially in bottles meant to be acidic and bright.

Bottom line? Winemakers don’t just hope for the best. They plan this part meticulously.

The Risks That Come with MLF

Like most behind-the-scenes operations, malolactic fermentation in wine has its share of challenges. When not monitored, it can go sideways:

• Spoilage risk: If the wrong bacteria get in, you might end up with funky, off-putting flavors.
• Loss of freshness: Some wines lose their zing if MLF goes too far. It’s a tradeoff—texture vs. brightness.
• In-bottle fermentation: If MLF kicks off after bottling, it can lead to gassy bottles, cloudiness, or worse—spoilage.

So no, it’s not a throw-it-in-and-walk-away process. It’s strategic, delicate, and has to be timed just right.

How to Spot a Wine That Went Through Malolactic Fermentation

You won’t see a big “MLF” sticker on the bottle, but if you pay attention, the clues are there:

• Taste: Creamier mouthfeel, softer acidity, maybe a hint of butter or brioche.
• Type of wine: If it’s a bold red or a full-bodied white, it likely went through MLF.
• Winemaker notes: Premium wines often detail the fermentation process on their back labels or websites.

Still not sure? Ask the sommelier or check the winery's site—they usually love talking fermentation.

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Final Takeaway: A Quiet Star in the Winemaking World

So, what is malolactic fermentation, really? It’s not just a scientific afterthought. It’s a stylistic move. A textural choice. A flavor decision.

Winemakers use MLF not to fix bad wine but to shape great wine. It’s how they turn sharp reds into smooth ones, or zippy whites into creamy, full-bodied glasses.

You might not taste malolactic fermentation wine and think, “Ah, lactic acid!”—but you will notice how balanced, round, and drinkable it feels. That’s MLF doing its job without needing the spotlight.

And now that you know what’s going on behind the scenes, you’ll never drink that glass the same way again.

Cheers.

This content was created by AI