Beer Geekery 101: International Bittering Units

This guy looks like Doc Brown

Most people, when picturing brewers in their minds, see either a medieval monk standing next to a wooden cask or one of those guys from the Sam Adams commercials with the long beards and the coveralls. Those guys do exist in real life, but in order to complete the image, there is one more brewer characterization that you need: the mad scientist - the guy in the white lab coat with the clipboard in one hand and a beaker in the other. This is the guy who is responsible for the science, and is where we find all sorts of measurements and acronyms, like the one I’m focusing on today.

The International Bitterness Units scale, or simply IBU scale, provides a measure of the bitterness of beer. You probably already know that bitterness in beer is provided by the hops used during brewing. An IBU is a standard unit of measure that is obtained through the use of a spectrophotometer and solvent extraction and determines how bitter the brew actually is. It is the result of an empirical formula whose development was based on tasting beer samples and correlating the perceived bitterness to a measured value which represented the total concentration of bitter compounds in the beer. In other words, a bunch of dudes and dudettes got together and drank beer, and then developed a system to compare and contrast different bitterness qualities (rough job). Sounds fairly simple right?

Here’s where it gets complicated: The bittering effect is less noticeable in beers with a high quantity of malt, so a higher IBU is needed in heavier beers to balance the flavor. For example, an Imperial Stout may have an IBU of 50, but will taste less bitter than an English Bitter with an IBU of 30, because the latter beer uses much less malt than the former. Or, more simply put, higher IBU doesn’t always equal more bitter.

Here’s a real-world example that I encountered last Thursday (which was #IPADay 2012). I had in front of me a bottle of Dominion Brewing Company’s “Double D” double IPA, as well as a bottle of DuClaw Brewing Company’s “Serum xxIPA” double IPA. Both are double IPA’s, so they have similar characteristics, but the IBUs were vastly different. The “Double D” flaunts 90 IBU’s and 10.2% ABV, while the “Serum” weighs in at 80 IBU’s and 9.0% ABV. It was clear to me when drinking them that the “Serum” was much more bitter tasting than the “Double D,” but as you can see, the “Double D” has the higher IBU level. The clue to figure this out is in the alcohol level, which is slightly higher in the “Double D” than it is in the “Serum.” This implies that Dominion used more malts in their brew which serve to balance out the hops. So while their higher hop load does read higher on the IBU scale, it appears more balanced on the palate and therefore, less bitter. The “Serum,” on the other hand, has less of a malt backbone so it tastes more bitter. Hopefully, I didn’t just make things more confusing.

The technical limit for IBU's is around 100. Some beers weigh in above 100 IBU’s, but the consistency of the measurement is lost when you get too far above 100 because there is no real gauge when it comes to taste threshold. It really becomes a marketing ploy when you get IBU’s that high. A light American lager might be as low as 5 on the scale, while a barley wine can range up to 100. Measures for other beverages include:

Spectrophotometer: High-speed equipment

■ Belgian Lambics: 11–23
■ Blonde ale: 15–30
■ Kölsch: 18–25
■ Märzen/Oktoberfest: 18–25
■ Ordinary English bitter: 20–35
■ Porter: 20–40
■ Brown ale: 15–25, with North American styles higher, 25–45
■ Bohemian-style Pilsener: 30–45, sometimes it can range up to 100 (e.g., German Bitterpils)
■ India Pale Ale: 40 or higher
■ An Irish stout like Guinness: 25–60

What a clown

Notice how low in IBU’s that American light lager is… no surprise there at all. Remember the old Keystone Light commercials with the bitter beer face? They were actually trying to sell lack of taste as a benefit. Losers.

When it comes to home brewing, where very few people want to pay for an actual spectrophotometer, there is a “simple” formula that is commonly used to calculate IBU. It’s not perfect, but its close enough for home use:

Wh × AA% × Uaa ⁄ ( Vw × 1.34 ), where

■ Wh refers to the weight of the hops used, in ounces

■ AA% refers to the alpha acid percentage, which is influenced by many factors, including cultivation method, species, and time of year — hops are often sold labeled with this percentage

■ Uaa is the percentage of alpha acid that is actually used during the boiling process

■ Vw means the volume of the wort, in gallons

■ 1.34 is a constant factor that adjusts the measurement to account for the use of U.S. customary units

There are several different methods for finding Uaa, which can yield very different results. Generally, Uaa increases with longer boiling times and decreases with higher boil density.

So now you have a very basic-level understanding of one of the units of measure that the beer geeks go on about. Although I am one of them, and I am all about waxing poetic on the characteristics and subtle nuances of different brews, I often wonder if calculating bitterness is anything more than bragging rights and marketing schemes. Does the exact value of bitterness really matter to the thirsty beer drinker? Probably not. However, it is interesting to note the relationship between hops and malt in a beer, and how that relationship affects the bitterness of the final product. Brewing science: Making our lives better and more miserable simultaneously since ancient Sumerian times.

Here’s to craft-brewed happiness… Cheers!