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In this episode of “Wine 101,” VinePair’s tastings director Keith Beavers explains the process of carbonic maceration. This simple but effective winemaking technique has been in use since ancient times but is experiencing a recent resurgence across the U.S. market — both for red wines and fruit beers.

Tune in to Episode 15 of the bonus season of “Wine 101,” and join Beavers as he breaks down the science and history behind carbonic maceration.


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Keith Beavers: My name is Keith Beavers, and let’s settle this once and for all: Is it ray-diator or rah-diator?

What’s going on, wine lovers? Welcome to Episode 15 of VinePair’s “Wine 101” podcast. This is the bonus season. Carbonic maceration: You may have heard this term being bandied about. It’s ancient. It’s fun. It’s awesome. It’s confusing. It’s scientific. Let’s get into it. It’ll be fun.

If you’re a wine lover, and you’re currently into the wine thing, trying wines and talking to people about wines, what’s very popular right now is this term called “carbonic maceration.” You may not recognize that term, but you may recognize it when someone says to you, “Hey, man, this is a carbonic red.” That’s so cool, but what does that mean? Well, the term is new and science-y, but the process is about as ancient as wine itself. It actually has to be, because of the way wine was made in ancient times. Let’s clear this up.

In 1872, Louis Pasteur did all that stuff with pasteurization. He came to the conclusion that grapes held in carbon dioxide have a different flavor than if they were just held in oxygen. When a whole grape is held in an anaerobic environment — an environment that completely excludes oxygen and is filled with carbon dioxide — carbon dioxide pushes all of the oxygen out of its atmosphere. And if a grape is held in carbon dioxide in an anaerobic environment for a while and then released into oxygen, crushed, and then fermented into a wine, the resulting aromas and flavors are considerably different than if grapes were made in the traditional way.

So, get this: If you were to take a vat and you were to carefully place bunches of grapes that still are on the stems, you put a cap on it, and you leave it alone for two to three weeks, what would happen is the lower layer of grapes would eventually get broken and crushed underneath the weight of all of the grapes above it. Those grapes release the juices, which start filling up a little bit into the tank. As those juices fill up a little bit in the tank, the yeast that’s in the air finds that sugar and begins a little bit of fermentation. As that’s happening, that fermentation is creating ethanol and carbon dioxide like it would any other time in any other fermentation. But this is where things get really crazy.

Carbon dioxide starts rising as it would in any vat, but as it rises, it does so to the level of grapes just above the crushed grapes. And those grapes are still whole, but they’re surrounded by the juice of the bottom layer of broken grapes. I’m sure some of those grapes might crack or break. But what’s happening here is that the layer is surrounded by juice, yeast, and CO2. That CO2 keeps rising, and it rises all the way to the top layer, so let’s say there are three layers within the vat. When you’re at the top layer, the juice hasn’t gone up there, but it’s all carbon dioxide. So what’s happening here is that carbon dioxide has pushed all of the oxygen out of the vat. It’s already at the top. So now all the grapes are pretty much covered in juice, yeast, and carbon dioxide. That carbon dioxide starts to soak into the whole and intact grapes. As the carbon dioxide soaks into those grapes, it brings or draws the anthocyanins and the tannins from the skins into the flesh of the grape and actually goes through a little bit of fermentation. It’s called intracellular fermentation, and this right here is where things start to change or pivot, like Ross. That will bring different aromas and vibes into the resulting wine.

With these intact berries, they lose about a fifth of their sugar. They also gain a little bit of alcohol strength by maybe 2 percent. They also increase tremendously in something called glycerol, which gives a sort of viscosity to a wine. And they lose about half of their harsh malic acid, that sharp acid that is converted into lactic acid during the malolactic conversion, which I talk more about in the white winemaking episode in Season 1. It also increases a little bit in pH, so it’s not sharp anymore. The sharpness of what’s happening inside these grapes is calming down due to its interaction with carbon dioxide. This is all happening within the intact berries. What’s even nuttier is, within this process, it’s thought that very unique flavor compounds are being formed.

I don’t want to go deep, deep, deep into the science here. But I find this so cool because within the flesh of grapes are these things called flavor precursors that will eventually be the primary aromas of a resulting wine after grapes are crushed and exposed to oxygen through the winemaking process. These are flavor compounds being created by whatever’s inside that flesh of that grape without having the oxygen exposed. So these grapes don’t even get a chance to have oxygen, and the carbon dioxide is creating something completely different. I just find this so wild. I hope you guys do, too.

If you read these compounds, you get a sense of the resulting flavor. While carbonic maceration is happening, compounds by the name of benzaldehyde, which is an almond compound. Vinyl benzene, which gives a sharp, sweet smell. Then there is ethyl cinnamate (cinnamon), ethyl vanillate (vanilla), and methyl vanillate. So you have almondy, sweet, sharp cinnamon, vanilla vibes happening during the carbonic maceration. Michael Flanzy, a southern French scientist in 1936, observed that grapes held intact for several days under CO2. Crushed and made into wine in a traditional method, they are brighter in color, less tannic, and have a distinct perfume to them. And when you sip red wine made from carbonic maceration, the common aromas you’re going to find are bananas and bubblegum. Yeah, it’s crazy. Also, if you know what Kirsch smells like, it has similar vibes. It’s basically just cherry or Morello cherry brandy. And that’s carbonic maceration.

That is the most ancient way wine can be made. Whenever you see the old illustrations of people stomping on grapes, that carbonic maceration happens. When you stomp on grapes, you’re crushing. This is essentially the oldest way of winemaking. And in modern wine times, carbonic maceration is famously known in the Beaujolais region of France when they use the grape called Gamay. It’s a process that is not happening as often these days as back in the day. But when we get to the Beaujolais episode, which I promise I will get to, we’ll get further into that.

But there’s a little twist to the story. What I just explained to you is carbonic maceration. But these days, that is now called semi-carbonic maceration. Because you’re letting the grapes do all the work for you and you’re coming back in three weeks. It’s a gradual, slow process. Today, there is something called “true” carbonic maceration. That is basically forcibly injecting CO2 into an atmosphere and making sure that all the grapes from the beginning have CO2. So we’re not waiting for grapes to get crushed, waiting for the yeast to find it, waiting for the yeast to eat it, or having the yeast do its thing. They’re carefully putting the grapes in the vat, as I said before. And then, they’re pumping CO2 into the vat so that when the natural crushing starts, carbonic maceration is immediately happening. And the majority of the grapes go through intracellular fermentation and give the majority of the fresh and fruity vibes they’re looking for.

Right now, the trend towards carbonic maceration seems to be pretty popular. What’s cool about it is that we’re just experiencing another way of winemaking that has been around for a long time. It’s finally hitting the market, and we’re actually able to enjoy it. They’re lower in alcohol, they are fruitier, and they’re easy to chill. They’re great by themselves with some cheese or friends. It’s a very social vibe with wines that have gone through carbonic or semi-carbonic maceration. Again, we’re going to do a Beaujolais episode, but have you ever heard of Beaujolais Nouveau? This is that vibe.

But nowadays, what we see in the United States is that carbonic maceration is just everywhere. There are grapes out there called hybrids. And if you listen to the phylloxera episode, I go through the hybrid stuff. And these are grapes that were a cross between French and American varieties, and these varieties often have a certain compound in them that give these odd, primal, foxy pheromones. It’s a little intense. If you throw hybrid grapes through the carbonic maceration process, the odds are better that the compound will not overwhelm the wine.

Hybrid wines are becoming popular on the market, especially in the United States, and a lot of them are going through this carbonic maceration. It’s a whole new category of wine to enjoy. These wines don’t age. They’re not going to develop. They’re ready to drink right now. Buy it, put it in the fridge, chill it down. Go buy your cheese, invite your friends over, pop it, drink it, repeat. You will see some vitis vinifera, I think Cab Franc is very popular right now for the carbonic maceration stuff. Maybe some Merlot, but you’re never going to see Cabernet Sauvignon. It’s often going to be a blend. Sometimes, it’ll be one variety, but it’s mostly going to be a blend and it’s going to be red. As far as white wine, you’re not going to see a lot of carbonic white. I don’t know what that entails. I’ve actually never had a carbonic white. One of my colleagues at VinePair said they had had a carbonic Moscato. That sounds kind of awesome.

But there you have it, guys. Carbonic maceration is so easy, right? So when you see it on the wine shelf, you’re like, “OK, let’s pop that open, chill it, and do the thing that Keith said.” All right, I’ll talk to you guys next week.

@VinePairKeith is my Insta. Rate and review this podcast wherever you get your podcasts from. It really helps get the word out there.

And now, for some totally awesome credits. “Wine 101” was produced, recorded, and edited by yours truly, Keith Beavers, at the VinePair headquarters in New York City. I want to give a big ol’ shout-out to co-founders Adam Teeter and Josh Malin for creating VinePair. Big shoutout to Danielle Grinberg, the art director of VinePair, for creating the most awesome logo for this podcast. Also, Darbi Cicci for the theme song. Listen to this. And I want to thank the entire VinePair staff for helping me learn something new everyday. See you next week.

Ed. note: This episode has been edited for length and clarity.