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

If you’ve ever opened a bottle of red wine and it pops softly as a wisp of fizz escapes, don’t panic. It’s not ruined and nothing is going to happen to you if you drink it.

It’s not quite like a corked champagne where the cork is trying to shoot across the room, but not quite still either. You pour it into a glass…and there it is: bubbles.

This isn’t a common occurrence, but if it happens, of course your mind is going to run run run. Is your wine ruined? Is this fermenting? I’ve heard of something called a fault…is that it?

It’s a fun and curious case of carbonated still wines, and I’d love to go into how malolactic fermentation could be quietly changing something in your glass.

What Is Malolactic Fermentation?

Malolactic fermentation (often called "malo" or MLF) is a secondary fermentation process used in many wines. Ehh, it’s also sort of a misnomer because it’s not really done with yeast, but bacteria. So, technically, it’s not really a fermentation at all, but…here we are, I didn’t name it.

During alcoholic fermentation, yeast turns sugar into alcohol. During malo, lactic acid bacteria—most often Oenococcus oeni—convert sharp malic acid, the kind that gives green apples their tartness, into the much softer lactic acid.

The change makes the wine feel rounder and smoother. It happens in most red wines and in certain whites, especially Chardonnay. Malo can also create diacetyl, the compound responsible for that familiar buttery aroma. Depending on how the winemaker manages the process, the effect can be obvious or barely noticeable.

Oenococcus oeni is particularly talented at surviving inside finished wine, which is not exactly a welcoming environment for most things out there. There’s plenty of alcohol, very little food left, and enough acidity to make most microorganisms reconsider their life choices. Have you ever heard of a microorganism having a life-crisis? I’m betting they do when they find themselves trapped in a bottle of wine.

Anywaaay, winemakers can allow the bacteria already present in the cellar to begin the process naturally, or they can add a cultured strain for more control.

As the bacteria convert malic acid into lactic acid, they also release a small amount of carbon dioxide. Once malo is complete, the wine is normally stabilized before bottling.

Normally being the key word here.

Sometimes the process stalls and it starts again later. Other times the little bacteria wakes up after the wine has already made it into the bottle. When that happens, the carbon dioxide has nowhere to go, and a supposedly still red wine can develop a faint little spritz that nobody ordered.

Why Is There Fizz in My Red Wine?

Okay, so back to the question at hand, when you open a bottle of red wine expecting the usual little sigh from the cork and instead, it pops, or there’s a slight prickling on your tongue, that’s probably not a bad thing.

Naturally, your first question is probably, “is this supposed to be happening?” There really are times where, yes it is. Lambrusco, sparkling Shiraz, Brachetto d’Acqui, and certain pét-nats are meant to bubble. Some low-intervention wines also keep a tiny bit of natural spritz, especially when they’re bottled young or described as “bottle-conditioned” (which sounds like something you put in your hair, but it’s not).

If you bought an ordinary bottle of still Cabernet or Barbera, though, the fizz probably wasn’t part of the original plan.

A small amount of carbon dioxide can remain dissolved in wine after fermentation. This is especially common in young wines that were bottled quickly, handled gently, or made with minimal filtration. The effect is usually subtle and disappears after a good swirl or a few minutes in a decanter. Fizz can also mean that something restarted inside the bottle. Yeast could be bouncing around in there, happily consuming residual sugar and beginning another alcoholic fermentation, or lactic acid bacteria may be finishing malolactic fermentation that never fully completed at the winery.

Both processes release carbon dioxide, but they aren’t the same thing. Yeast refermentation needs fermentable sugar while malolactic fermentation doesn’t. Like I said earlier, during malo, bacteria convert malic acid into softer lactic acid and release carbon dioxide along the way. If that happens after bottling, the gas has literally nowhere to escape (help, I’m trapped!!), so your still red wine starts developing a little personality it wasn’t supposed to have.

Without laboratory testing (which might be extreme), you usually can’t identify the exact cause from the bubbles alone. You can still collect a few clues along the way though!

A faint spritz that quickly disappears is probably leftover dissolved carbon dioxide. Stronger pressure, persistent bubbles, cloudiness, new sediment, or a noticeably yeasty aroma may point toward refermentation. In-bottle malo can also create haze or sediment, along with softer acidity and occasionally buttery, creamy, or strangely lactic aromas.

None of these clues are absolute, because wine enjoys being complicated whenever we would prefer a straightforward answer.

Is Fizzy Red Wine Safe to Drink?

A few unexpected bubbles don’t automatically make a wine dangerous. Most of the time, this is a wine-stability issue rather than a health emergency. I doubt you’ll get sick from it unless you go ham and drink too much of it. Hydrate please.

Start by smelling the wine though. Wet cardboard points toward cork taint or a weird barnyard, Band-Aid, or sweaty leather aromas can come from Brettanomyces. Vinegar or nail-polish remover smells suggests high volatile acidity. Those are separate wine faults, and the bubbles themselves don’t diagnose any of them.

Then taste a small amount. If the wine smells clean, tastes balanced, and only has a tiny prickle that fades after swirling, it’s probably fine to drink. Decanting it for twenty or thirty minutes can help the remaining carbon dioxide escape if you’re ready to say goodbye to those bubbles.

A bottle with obvious pressure deserves more care. If the cork is beginning to push out, wine is leaking around the closure, or the bottle gushes when opened, chill it thoroughly and point it away from your face for the love of God. Fermentation inside a sealed bottle can create considerably more pressure than the winemaker intended, and nobody needs to be taken out by an angry Merlot.

What Sulfites Have to Do With It

Sulfites help protect wine from oxidation and suppress unwanted yeast and bacterial activity. They’re useful, but they’re also not a magical force field surrounding the wine.

Their effectiveness depends partly on the wine’s pH and the amount of sulfur dioxide present. Winemakers also rely on clean equipment, completed fermentations, temperature control, filtration, and proper bottling practices to keep a finished wine stable.

When a wine contains very little sulfur, hasn’t been filtered, or still has residual sugar or malic acid, microorganisms coud hang out in there and remain active. Give them the right conditions and they can begin working again after the bottle leaves the cellar.

This is one reason unexpected fizz appears more often in some natural and low-intervention wines. A producer may accept a little haze, sediment, bottle variation, or gentle spritz as part of the style. Sometimes it’s charming and other times it’s simply an unstable bottle wearing a very good philosophical outfit.

“Natural” doesn’t automatically mean that every surprise was intentional, and it’s important to remember that while all the “Natty” Sommeliers try to shove it down your throat. I like a good natural wine as much as the next person, but the wine needs to taste like it was actually made on purpose, not by accident.

Should You Send It Back at a Restaurant?

If the wine was sold as a sparkling or lightly pétillant style, enjoy the bubbles. That’s what you ordered.

If the wine was meant to be still, swirl it and give it a minute. A tiny amount of residual carbon dioxide may disappear almost immediately. When the fizz remains noticeable, the wine tastes unbalanced, or the bottle shows signs of refermentation, ask the sommelier or server to taste it.

You don’t need to diagnose the microbiology tableside. You can simply say, “this seems unexpectedly fizzy. Is that typical for this wine?”

A good sommelier should know whether the spritz is intentional. If it isn’t, sending the bottle back is completely reasonable. You ordered the wine the producer intended to make, not the weird sequel it started writing inside the bottle.

Can You Still Enjoy It?

Sometimes the wine tastes perfectly good once the extra gas blows off. Pour it into a decanter, swirl it a few times, and let it sit. Slightly chilling the bottle can also make an overly lively red feel more composed. A little sparkle works especially well with salty, fatty food, which happens to be my favorite sort of food to eat. Think cured meats, pizza, burgers, duck, pâté, creamy cheese, or anything fried. That’s part of the reason Lambrusco feels so perfect beside salumi and Parmesan. Acidity refreshes the palate, and bubbles provide a little extra scrubbing power.

Still, pairing advice shouldn’t become an excuse to rescue a wine that tastes genuinely bad. Sometimes the bottle is flawed, I mean…it happens.

Wine is always changing in the bottle. Usually the winemaker manages to slow that process down before bottling, but every once in a while, though, the wine decides it still has something left to do.

If you’re headed on a cruise anytime soon, check out my website Cruising With Wine to find the best places to stop along the way to find some truly remarkable wines.