Now that experimentation seems to be shifting from Belgian styles to hoppy ales, the IBU — international bitterness unit — has assumed new importance. IBUs primarily measure iso-alpha acids, the chief bittering compound in hops. The scale was devised in the 1950s to help brewers keep their recipes consistent from batch to batch. Today, IBU levels are often trumpeted on beer labels, brewery Web sites and supermarket placards, a way of bragging that my beer is bigger than yours.
The measurement does help consumers compare one style with another. In American-style lagers such as Budweiser, the IBU level (typically 12 or below) barely pokes through the threshold of taste. A hoppy Pilsener, at 20 to 30 IBUs, will have a pronounced bitter character. An IPA, at 50 to 60 IBUs, should slap you across the face with hops.
As a result of the public’s craving for ever-hoppier beers, craft breweries are taking IBUs into the stratosphere. El Dorado Single Hop Imperial IPA, from Flying Dog Brewery in Frederick, measures 70 IBUs. Enjoy By 02.15.13 IPA, from Stone Brewing in Escondido, Calif., clocks in at 88. Palate Wrecker, from Green Flash Brewing in San Diego, measures “in excess of 130 IBUs,” according to brew master Chuck Silva (although he admits the lab tests weren’t really calibrated to measure concentrations that high).
Some claims verge on the absurd. BrewDog in Fraserburgh, Scotland, a few years back released Nanny State, a supremely unbalanced brew that in its original version measured 1.1 percent alcohol and a purported 225 IBUs. Denmark’s Mikkeller brewery once marketed an imperial IPA called 1000 IBU.
If Palate Wrecker is named for its ability to numb your taste buds, what would a 1,000-IBU hop monster do? Burn a hole in your tongue?
Don’t believe everything you read on a label, cautions Mitch Steele, brew master for Stone. “Most values on craft beer bottles are not analytical measurements; they’re calculations,” he says.
The iso-alpha acids would reach a saturation point long before the 1,000 (or even the 200) mark is reached. What’s more, adds Steele, a beer can shed 25 to 30 percent of its IBUs during fermentation. As the pH drops, some of the acids turn to solids and have to be strained out.
More important, iso-alpha acids alone won’t help you attain hop bliss. “There are 300 to 400 compounds that have been identified in the essential oils of hops,” says Thomas Shellhammer, professor of fermentation science at Oregon State University. “There could be as many as a thousand.”
Those essential oils distinguish one hop strain from another, imparting the aromas we describe as spicy, floral, citrusy, resiny and grassy.