Plenty of us know that “nitro” has something to do with why Guinness comes out all creamy and smooth, with the classically foamy head that seems to somehow cascade in majestic slow motion—or maybe we’re just thirsty. What plenty of us don’t know is why so-called nitro pours are becoming more common.
Over the past few years, nitrogen’s been gassing up beers well beyond everyone’s favorite default Irish stout—breweries like Sixpoint (Otis Sout), Yards (Love Stout), Sly Fox (O’Reilly’s Stout), Nevada Brewing Co. (English Mild Ale), and Left Hand (a whole series) are all incorporating nitro into their programs. So…why?
Well, for this we have to do a (mild) chemistry lesson. But it involves beer, so stay tuned. Most beers are carbonated with CO2, which creates that lively, plucky, poking-around-in-your-mouth sensation that explodes bits and pieces of hops and malt around your palate. But some beers are carbonated with a mixture of nitrogen (70%) and CO2 (30%). And that’s a whole other story.
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The basic—and no doubt rough—science for you: nitrogen is mostly insoluble in liquid (which is why you don’t end up with a lot of prickly bubbles in a nitro beer). Instead, what you get is a gas that helps buoy up that creamy head. According to at least one source (Draft magazine associate editor Kate Bernot, ahem), “nitrogen bubbles are smaller than carbon dioxide bubbles, meaning beers don’t feel as carbonated when served on nitro.” It could also be argued that CO2 will do a better job of shunting those good volatile aromatic compounds up your nose, while nitrogen keeps things a bit more contained. Meaning the use of nitro mostly has to do with a brewer’s goals.
When they’re poured on draft, nitro beers are forced through something called a “restrictor plate,” which allows the nitrogen to emerge and help that big, bloomy, off-white head to puff up like a beautiful liquid mushroom on top of your glass. (Cans of Guinness are nitrogenized using “widgets,” basically little plastic balls filled with beer and nitrog\en that, upon opening the beer, release and create a similar effect as a draught-poured beer; the widget’s also the thing that creepily rattles around in your can of Guinness after you’re done with it.)
But other breweries are opting for nitro over CO2, reasons being it not only impacts texture—yielding a smoother mouthfeel—but flavor perception. As Frankenmuth Brewery notes “malt heavy beers, like stouts and porters, greatly benefit from [nitro] as it helps evenly distribute their complex flavors.” Of course, not all beers benefit from a smoother mouthfeel—it wouldn’t work well for something aromatic and lively, like an IPA—which is likely why most breweries won’t convert to an all (or even partially) nitro system.
Of course, because this is beer—the land of alcoholic experimentation—Guinness is introducing a Nitro IPA. Check it out and let us know. As ever, the proof is in the drinking.