Picture one of those long days, when all you want to do is sit in your favorite recliner and enjoy a cold one. You lift the glass to your lips and take a sip only to find the cardboard, waxy, or even caramel taste of stale beer turning your tastebuds to funk. Well, one group of researchers is trying to help solve that problem: A new smartphone app designed by Spanish chemists detects whether or not your beer is stale before you wet your whistle.
The process devised by scientists at Complutense University of Madrid allows brewers to use sensors to measure levels of furfural, a chemical compound reported to give beer a stale flavor. The sensors are controlled via smartphone app, and change color when they come into contact with the furfural. But while that sounds pretty slick, it’s aimed at the industry, not the average beer drinker. And relying solely on furfural is dubious, says Ray Daniels, founder of the Cicerone beer certification program. “For starters, using furfural as a staling marker is a new one on me,” Daniels says. “So, I wouldn't bemoan lack of access to that app.”
One way Daniels says you can check for stale beer on your own is by the smell. Many drinkers complain of a "papery" note in stale beer, which can be detected on the nose. More subtle is a waxy or caramel smell, which will be notable in the palate. That caramel taste comes from what Daniels calls “malt shift,” a slow increase in caramel flavor as malty brews (like brown ales and stouts) age. In hoppier beers like IPAs, hop notes can start to fade and become less vibrant as soon as 90 days after bottling, and over longer periods, they’ll start to lose their bitterness. And if your beer starts to taste like wine or whiskey, or starts giving off leathery notes, those are surefire signs of old beer. “This is where style knowledge and tasting experience come into play,” Daniels says. “And this is why we train and test industry professionals on how to identify flawed beer, because often times the consumer can't really know if the beer is off or not — even if they aren't really happy with it.” So, until an app comes along for us regular folk, rely on your nose, and that whole, you know, talking to your bartender thing.