Malolactic Fermentation: Because Wine Needed Butter Too

If you’ve ever taken a sip of Chardonnay and thought,

“Hmm… this tastes like it’s been lightly basted in butter,”

congratulations — you’ve met malolactic fermentation, or “malo” if you’re on nickname terms.

Malolactic fermentation is the bit in winemaking where things get creamy. Literally. It’s not fermentation in the yeast + sugar = booze sense — that part’s already happened. This is the next stage. The spa treatment. The makeover montage. Where sharp, zippy malic acid (think green apples and awkward acidity) gets mellowed into soft, round lactic acid (think Greek yoghurt and smug silkiness).

It’s done by bacteria, not yeast — specifically Oenococcus oeni, which sounds like a Harry Potter spell but is really just the nerdy microbe making your Chardonnay smoother than your ex’s apologies.

Why should you care? Because this sneaky little process changes how a wine feels, tastes, and makes you sound very clever at dinner parties.

Malolactic fermentation reduces sharp acidity, softens texture, and brings in those comforting, creamy notes people either love or pretend to hate. And while it’s often associated with buttery whites, it’s also behind the plush mouthfeel in loads of reds.

In short: malolactic fermentation is the difference between a wine that slaps and a wine that seduces. And who doesn’t want to know about that?

The Science Bit — But Sexy

Right, time for a bit of science — don’t worry, no one’s grading you.

Malolactic fermentation is a secondary bacterial process that usually kicks in after the alcoholic fermentation has wrapped up. Instead of yeast doing the work, lactic acid bacteria take the stage, specifically Oenococcus oeni (say it with a French accent — you’ll sound credible).

Their job? Turning malic acid (tart, edgy, thinks it’s better than everyone) into lactic acid (creamy, soft, maybe teaches yoga). This isn’t about alcohol production. It’s about texture transformation. Think green apple vs. milk. Malic acid bites. Lactic acid hugs.

The by-product? A bit of carbon dioxide (not enough to sparkle) and diacetyl — the real MVP of the process. Diacetyl is what gives wine that iconic buttery aroma. You’ll smell it and think: “Popcorn?” Congratulations, your palate is now accidentally educated.

Winemakers can control how much malolactic fermentation takes place. Some allow it naturally. Others encourage it. Some stop it cold with a dose of sulphur dioxide like a wine-based crime scene. Why? Because not every wine should be soft and creamy. Sometimes you want those edges.

The whole thing is a bit like skincare: some wines need exfoliating. Others? A rich, silky moisturiser. Malolactic fermentation is the latter.

Butter, Cream, and the Chardonnay Controversy

Ah, Chardonnay — the wine that launched a thousand opinions. And nothing divides a room of wine lovers faster than the question: “Do you like it buttery?”

If your Chardonnay tastes like a croissant with a splash of oak, chances are it’s gone through full malolactic fermentation — and someone made damn sure of it. That soft, oily mouthfeel? That wave of toasted brioche and lemon curd? That’s malo magic with a side of oak influence.

Some people adore it. Others act like buttered Chardonnay personally insulted their dog. The “Anything But Chardonnay” (ABC) crowd rose to fame precisely because of this — sick of over-oaked, over-malo’d whites that felt more like desserts than drinks.

But here’s the twist: not all malolactic Chardonnays are butter bombs. In the Burgundy region, especially Meursault and Puligny-Montrachet, malolactic fermentation is often used — but elegantly. There, it’s more silk than slime. More cream than custard.

In contrast, New World Chardonnays (hello California and Australia) often go full dairy. Malolactic + oak = “buttery oak bomb” — sometimes glorious, sometimes like licking a barrel of ghee.

The key is balance. Diacetyl (that buttery compound) is not inherently evil. Overdone, sure. But used with restraint? It’s the thing that turns a sharp, acidic Chardonnay into something lush and luxurious.

So next time someone says, “This Chardonnay tastes buttery,” you say, “Ah, classic malolactic signature — probably full malo with moderate oak integration.” Then casually sip and feel superior.

Malo in Red Wine: The Unsung Smoother

While Chardonnay gets all the buttery limelight, red wines are actually doing malolactic fermentation all the time — they just don’t brag about it.

In fact, most still reds go through malolactic fermentation as a standard part of winemaking. Not because they want to taste like dairy products (ew), but because reds need less sharpness and more smooth swagger. Nobody’s sipping a Cabernet and thinking, “Hmm, this could use more acid.”

Malo in reds is all about mouthfeel and structure. It softens tannins, rounds out the texture, and helps reds taste cohesive — like a well-dressed bouncer at a wine bar: firm, but smooth.

You won’t find the same buttery flavour profile here because red wines are full of so many other big characters — tannins, oak, dark fruits, spice, and self-importance — that diacetyl barely gets a word in. It’s less about flavour, more about feeling. Reds become less angular, more plush. Less “just punched you,” more “firm handshake and knowing nod.”

In some natural or minimal-intervention wines, winemakers might skip malo on reds — especially if they want to preserve that zippy acidity or bottle early. But this is rare and usually done on purpose (or because they forgot).

So yes, malolactic fermentation is quietly making your reds smoother without shouting about it. No cream, no croissants — just the vinous equivalent of switching from skinny jeans to cashmere joggers.

How to Spot a Wine That’s Gone Full Malo

Malolactic fermentation doesn’t come with a neon sign — but your senses are smarter than you think.

Start with your nose. Diacetyl, that buttery compound, is the big giveaway. Think buttered popcorn, cream, or that weird moment in a Chardonnay where you wonder if you accidentally poured melted Lurpak into your glass. That’s a wine that’s probably undergone full malolactic fermentation.

Then there’s texture. Wines that have gone through malo tend to feel softer, rounder, creamier. Less angular, less like lemon juice spiked with adrenaline. More like a satin pillow that also gets you drunk. This is especially noticeable in whites — where the transformation from “sharp and citrusy” to “smooth and mellow” can be dramatic.

In reds, it’s more subtle. Malolactic fermentation in red wines is like a discreet stylist — not changing the outfit, just making sure it fits better. You’ll get a rounder mouthfeel, softer edges, and less acidic bite. But don’t expect butter. Expect balance.

And then there’s context clues. A winemaker will usually mention malolactic fermentation on the back label if it was intentional and they’re proud of it. Especially if they’re selling a buttery Chardonnay or a “creamy” white. In fancier places like Burgundy, they’ll never say it — you’re just supposed to know, darling.

Pro tip: if the wine tastes like dairy and citrus had a baby, congratulations — that’s the work of malolactic fermentation, and you are now 17% more smug than your dinner guests.

Champagne, Chablis, and Other Places It Gets Political

Ah, sparkling wine. Where bubbles rise, tempers flare, and malolactic fermentation becomes a matter of philosophy.

Let’s start with Champagne — the Paris Fashion Week of wine. In Champagne, the choice to allow or block malolactic fermentation is a big deal. Some producers go full malo to soften the wine’s intense acidity, especially in cooler vintages. Others block it entirely with sulphur dioxide or temperature control, arguing that high acid is what gives Champagne its age-worthiness and je ne sais quoi.

Maison Krug? Famously anti-malo. Ruinart? More relaxed. It’s like the sparkling wine version of whether you put cream or jam first on a scone. Everyone has an opinion. No one agrees. And someone’s definitely offended.

Now let’s talk Chablis, the coolest and most aloof of all Chardonnays. Here, winemakers are torn between preserving razor-sharp acidity and adding just enough malo to make things interesting. The result? Some Chablis are zippy and lean. Others are subtly creamy, like someone whispered “butter” into the barrel and then left.

In warmer regions, like California or South Africa, blocking malo is harder — the wines naturally have less acidity to begin with. So winemakers often let it happen, but balance it out with fresh fermentation practices or oak management.

Basically, malolactic fermentation becomes less about science and more about style. It’s not a rule — it’s a tool. And in the hands of the right winemaker, it can turn “decent” into “dangerously drinkable.”

Winemakers, Yeast Whispers, and the Art of Letting Go

Malolactic fermentation doesn’t always behave. And winemakers? They’re a bit like helicopter parents trying to “guide” a very rebellious teenager.

Some let it occur naturally, letting bacteria do their thing when the wine says it’s ready. Others inoculate — adding commercial cultures to make sure things happen on schedule (a bit like sending the wine to boot camp). Then there are those who block it completely, terrified of the buttery chaos that might ensue.

Controlling malo is tricky. You can manage temperature, sulphur levels, and oxygen exposure. But once it starts, it can take days, weeks, or months to finish. And if the conditions aren’t quite right? You’ll get stuck malo. Which, like a stuck sourdough, is a real pain — and could ruin your entire batch.

The most fascinating part? Malo can happen in bottle. If the wine wasn’t properly stabilised and still contains active bacteria, that round Pinot Gris you just opened might decide to go full dairy on you. It’s rare. But it’s real. And if your white suddenly smells like buttered cauliflower? Well… surprise.

For winemakers, malo is about control vs. chaos. Letting go just enough to let the wine evolve — but not so much that it throws a tantrum on the shelf. It’s a dance. With bacteria. In barrels. And somehow, it’s what makes your wine smoother.

Final Sip: Why Malolactic Fermentation Deserves Your Respect

It’s easy to mock malolactic fermentation. It’s got a clunky name. It’s done by bacteria. And half the time, it makes your wine smell like a dairy aisle.

But here’s the truth: malo matters. Without it, red wine would be harsh, sour, and practically undrinkable. Chardonnay would never have become the global queen she is. And Champagne? It wouldn’t be nearly as nuanced.

Malolactic fermentation is the quiet workhorse of winemaking. The thing that softens acidity, adds complexity, and — yes — creates those rich, buttery flavours some people secretly love but won’t admit to out loud.

You don’t have to like the wines that use it. But you should absolutely understand them. Because once you spot it, you start to see wine differently. You realise that what you’re drinking isn’t just grapes and yeast — it’s chemistry, craft, and a bit of microbial magic.

So the next time someone sneers at a creamy Chardonnay or says “this wine’s too soft,” just smile knowingly and say:

“Ah. Malolactic fermentation. A classic.”

Then swirl. Sip. And toast to the bacteria that made your wine better.