Nitro cold brew is bubbling up in coffee shops almost everywhere. The nitrogen-infused beverage became one of the hottest new offerings for coffee lovers looking for something different.

The cold brew — made by steeping coffee grinds in cold water for multiple hours — is dispensed from a stout tap, similar to what you’d find at your local bar.

The nitrogen bubbles give the cold brew a silky smooth texture and enhance its flavor — something coffee can lose when brewed the regular way, according to Matt Hartings, a chemistry professor at American University.

Hartings says coffee’s flavor compounds decompose when reacting with oxygen in the air during brewing. “When you bubble nitrogen through, you get rid of any oxygen that's in your coffee. And so you preserve all these flavors that might not be there otherwise,” he tells Here & Now’s Jeremy Hobson.

Nitro cold brew got its start a few years ago in Austin, Texas, and Portland, Oregon. It’s boomed as a millennial favorite and has since flowed into mainstream coffee chains such as Starbucks, which implemented the drink in 2016.

So what’s the magic driving it’s popularity?

“I think there's a lot of it that is a big marketing ploy or just we go into a coffee shop and you see someone pulling a tap and you think, 'I’ve got to have that.' So there is some psychological thing that's hitting you,” Hartings says. “The biggest difference I think is in the texture of the nitro cold brew coffee. And so if you put any sort of creamer in your coffee, it changes the mouth feel. When you add bubbles, it has the same effect.”

Interview Highlights

On making nitro cold brew

“It does look like a Guinness. To get that sort of falling cascade of bubbles that makes Guinness so iconic, and what nitro cold brew is starting to be, you really just put a lot of nitrogen pressure around the coffee itself. And you can take all that nitrogen from the air and you just bubble it right through your coffee.”

On using nitrogen in food and liquids

“We have been playing lots of games with our food lately. It's always fun to play with your food. I teach chemistry of cooking in American University. I tell all my students, 'Play with your food.' So there are a couple of roasters and a couple of coffee places that kind of figured it out at the same time probably about six or seven years ago that you could put nitrogen into your coffee and it changes the texture of the coffee and it changes the flavor a little bit too.”

On nitro cold brew’s taste

“Just starting with the coffee beans, if you can smell your coffee beans, those aromas are no longer in your coffee. And so doing cold brew in itself is one way to preserve some of the flavors that might escape really quickly when we do regular, hot brewed coffee.”

On whether nitro cold brew is more caffeinated than regular cold brew

“So it depends. It depends on how they make it. With any cold brew, because you're steeping the grounds longer, you have the potential to get more caffeine out of your coffee than you would otherwise. So if I use a really coarse grind instead of a medium grind or a fine grind, that course grind I'm going to pour more caffeine out of that in comparison to a hot brew coffee if I use the same coarse grind. So it is definitely reasonable that you're gonna get more of a caffeine kick from any cold brew coffee. It's just a matter of how they make it.”

On recent trends in food chemistry

“Well we're getting into summer and so I'm thinking more about ice cream right now and I'm also thinking about flavor combinations. How do you put weird ingredients together and make them taste really good? So there's this great book called "The Flavor Matrix" by James Briscione and some of the flavor combinations that he uses in there include cilantro and strawberry. That's a really weird one. I just saw recently in his book as a potential pairing are beets and rum so new flavor combinations that can really excite our palates in different ways.”

Ciku Theuri produced and edited this interview for broadcast with Tinku Ray. Serena McMahon adapted it for the web.

Correction: "The Flavor Matrix" author mentioned in the audio version of this story was mistakenly identified. We regret the error.