Why Starbucks is pumping nitrogen into its coffee
Starbucks welcomed summer by announcing that its stores in seven cities would begin selling the hottest thing in chilled coffee: nitro cold brew.
But what actually is nitro brew, and is it really any different from cold brew?
Nitrogen-infused cold coffee has its roots in early 2013, when a food scientist at Stumptown Coffee Roasters in Portland, Oregon, named Nate Armbrust wanted to make cold brew coffee tastier.
So he decided to try pumping nitrogen gas into the brew.
Turns out this was a very good idea.
After a few months of playing around with the right balance of bubble infusion, according to Chemical and Engineering News, his nitrogen-infused cold coffee became creamier and richer than regular old cold brew - an instant hit after putting it on tap at his Portland cafe.
But how does it work?
When someone says that a beer is "on nitro," they're referring to the type of gas bubbled into the drink. Breweries typically use carbon dioxide to give a beer its quintessential bitter fizz. But sometimes a drink calls for a sweeter, silkier experience. So brewers commonly infuse darker, smoother stouts and ales - like Guinness and Old Speckled Hen - with nitrogen rather than carbon dioxide.
The creamier taste - either in beer or in coffee - is due, in part, to the smaller nitrogen bubbles.
Nitrogen gas doesn't easily dissolve in water, giving the brew a thicker, more velvety "mouthfeel." To get nitrogen into the liquid, the tap needs a "restrictor plate" to squeeze the drink through tiny holes, giving the beverage a particularly smooth and frothy head.
The tiny bubbles make the drink feel thicker when you gulp it down.
Some say that cold brew is already inherently tastier than conventional hot coffee because of its deeper, less acidic flavor notes. And some coffee snobs suggest a nitrogen tap process makes it even more amazing.
On the other hand, scientists aren't really sure why this might be, other than the improved mouthfeel.
One theory is that the nitrogen-infusion slows the degradation of coffee compounds. These compounds break down in a way kind of like how iron rusts when it's exposed to too much oxygen - giving the coffee a sour and bitter taste.
This oxidation is cumulative. When coffee sits for too long, the coffee's compounds continue to become oxidized, getting more and more bitter the longer it sits.
The nitrogen is likely making coffee more stable by "pushing oxygen out of the liquid," Matthew Hartings, a professor of food chemistry at American University, told Chemical and Engineering News - thereby extending its shelf life and slowing this oxidation.
Since a delicious cup of coffee depends on many factors - including the type and roast of the bean, how the beans are ground, how long you brew the coffee for, and the temperature and purity of the water used in the brewing process - nitrogen is not going to magically save the flavor of a batch of coffee that tastes bad to begin with.
That all being said, coffee snobs are loving this new way of drinking cold brew.
Because nitro coffee requires a special tap, Starbucks is only rolling it out in about 500 stores in seven cities by the end of the summer. According to Buzzfeed, a cup will go for $3.95 - a dollar more than straight-up cold brew.