Does Your Wine Pop a Little When You Open It? Malolactic Fermentation in the Bottle and the Sparkle You Didn’t Expect

Jun 12

You open a bottle of red wine. It pops softly. A wisp of fizz escapes.

Not quite a corked champagne, but not quite still either. You pour it into a glass…and there it is: bubbles.

Is your wine ruined?
Fermenting?
Faulted?
Or could it be something more interesting?

Let’s dive into the curious case of carbonated still wines, and how malolactic fermentation might be quietly rewriting the script in your glass.

What Is Malolactic Fermentation?

Malolactic fermentation (often called "malo" or MLF) is a secondary fermentation process used in many wines.

Instead of turning sugar into alcohol (like primary fermentation), it transforms harsh malic acid (the stuff that gives green apples their tartness) into softer lactic acid (think milk or cream).

The result?
A rounder, smoother mouthfeel. It’s what makes some Chardonnays buttery, or what gives red wines a silky polish.

MLF is done using a bacteria called Oenococcus oeni. Once the process finishes, most winemakers stabilize the wine, but sometimes, malo keeps going. And sometimes, it wakes up again in the bottle.

Meet the Microbe: Oenococcus oeni

It doesn’t get the spotlight like yeast does, but Oenococcus oeni is one of the quiet architects of great wine.

This little bacterium is responsible for malolactic fermentation…that process of turning sharp malic acid into softer, smoother lactic acid.

You’ll find it naturally present in many wine cellars, clinging to barrels, tanks, and sometimes even grape skins.
Winemakers can let it happen on its own, or add a cultured strain to guide the process more precisely.

Unlike yeast, O. oeni doesn’t feast on sugar.

It consumes acid.
And in doing so, it takes the edges off a wine, mellowing the profile and adding that creamy, almost milky texture you find in buttery Chardonnay or polished red blends.

Its actually eating some of the carbon of the acid structure and in the process, transforming it into another kind of acid.
It's sensitive, slow-working, and thrives in low-nutrient, high-alcohol environments, just like the inside of a finished wine.

Some winemakers love it.
Others fear what happens when it acts without permission.
But one thing’s certain: without this gentle bacterial alchemist, many of our favorite wines would taste far more aggressive.

Why Is There Fizz in My Red Wine?

If your wine pops or fizzes slightly when opened, it could be one of two things:

Residual carbon dioxide from fermentation that wasn't fully off-gassed.
Unfinished malolactic fermentation that reactivated in the bottle.

The second scenario is rare but fascinating.
If malolactic fermentation resumes inside the bottle (especially if the wine was bottled too early or without proper sulfur), it can create gas, pressure, and that curious effervescence.

This doesn’t mean your wine is bad …but it is unexpected. And in some cases, it becomes a feature, not a flaw.

Is It Dangerous to Drink?

No. In most cases, lightly fizzy red wine isn’t harmful.

It may be unusual, but unless the wine smells rotten, vinegary, or like wet cardboard (which could indicate a fault like Brettanomyces or TCA), it’s probably safe.

That said, fizz where it doesn’t belong can indicate instability in the bottle. If you’re aging wines, this one should be drunk sooner rather than later.

When Carbonation Is the Whole Point

Some winemakers intend for their wines to have a bit of sparkle. Meet the rebels:

Lambrusco (Italy): A naturally fizzy red that embraces its frizzante charm.
Pétillant-Naturel (Pét-Nat): Bottled before fermentation finishes, creating light bubbles.
Sparkling Shiraz (Australia): Rich, spicy red with celebratory fizz.

In these cases, the fizz is deliberate…a nod to joy, surprise, and fermentation as performance art.

The Forgotten Bottles That Surprise You Years Later

Sometimes it’s the bottles you leave behind…the ones tucked in the back of the wine rack, forgotten under dust…that come alive unexpectedly.

You open it expecting quiet, and instead, it hisses.

A whisper of carbonation rises, and your first sip crackles faintly on the tongue.
It’s not quite pét-nat, not quite still…it’s liminal.

These accidental re-fermentations feel like the wine has been thinking, dreaming, doing unfinished work. And maybe, it has.

The Role of Sulfites in Keeping Wine Still

Sulfites are often misunderstood, but in truth, they’re the peacekeepers of a bottle’s inner world.

Their job?

To silence yeast and bacteria once the winemaker is ready to bottle calm.
When sulfite levels are too low (or omitted entirely in natural wines) the door stays open for fermentation to sneak back in.

That’s how you end up with a wine that fizzes not by design, but by rebellion.
In low-intervention winemaking, sulfites are not villains, but sometimes, their absence is the source of the sparkle.

When Malolactic Fermentation Goes Rogue

MLF is usually completed under the watchful eye of the winemaker, but when it doesn’t fully finish, or when the wine is bottled too early, things can get lively.

The bacteria can lie dormant, waiting for the right conditions…just enough warmth, just enough sugar.

Then one day, inside your bottle, they wake up.
They stretch, they eat, they release carbon dioxide, and your still wine is still no longer.
It’s a reminder that wine isn’t a product.
It’s a process.

The Tactile Beauty of Micro-Bubbles

There’s something oddly intimate about tiny, unexpected bubbles in a glass of red.

They don’t scream like Champagne…they whisper.

They dance up the sides like nervous thoughts.
They change the texture of the wine, sharpening the acidity, lifting the aroma.
Even when they weren’t invited, they add something strangely alive. Maybe not elegance…but curiosity.

What to Pair With a Slightly Fizzy Red

When a wine surprises you with effervescence, lean into the moment.

Slight fizz pairs beautifully with fatty or salty foods…like duck confit, pâté, or creamy cheeses.

The bubbles cut through richness the way acidity does, but with a more playful edge.
Think tapas.
Think funky natural cheese and rustic bread.
The unexpected sparkle becomes a palate cleanser, not a flaw.

Should You Send It Back at a Restaurant?

If a still wine pops or fizzes in a restaurant setting, what’s the etiquette?

The answer lies in intention.
Was the wine meant to be still, or is this part of its natural, unfiltered charm?
A good sommelier will know the difference, and will welcome your questions.
If the wine smells good and tastes balanced, enjoy the quirk.

If it smells off, sending it back isn’t rude…it’s respect for the bottle and your experience.

Why Some Winemakers Embrace the Chaos

Not every winemaker wants control.

In the world of low-intervention and natural wines, chaos is part of the philosophy.
A little fizz, a little haze, a bit of bottle variation…these aren’t mistakes.

They’re the wine continuing to speak after it leaves the cellar.
For these producers, a slight pop isn’t an error.
It’s a personality trait.

How Common Is This? (And Why It Might Be Growing)

Malolactic-in-the-bottle isn’t widespread, but it’s more likely with:

Natural or low-intervention wines
Wines with minimal sulfites
Early-bottled reds or unfiltered wines
Small producers pushing stylistic boundaries

In the natural wine scene, a bit of haze or fizz isn’t taboo, it’s a conversation. You might even see "bottle-conditioned" on the label.

A Sommelier's Take: What to Do When Your Wine Pops

When I first opened a bottle and heard that tiny hiss, I froze. The wine was a Barbera…meant to be still, elegant, dry. But there it was: a whisper of sparkle.

I poured, swirled, sipped. It was alive. Not flawed. Just…dancing.

So here’s what I do now:

Taste it before judging.
Decant it if the fizz feels distracting.
Pair it with something fatty (like cheese or duck).

And I remember that wine is a living thing. Sometimes it finishes what it started…even years later.