You can’t have an in-depth conversation about beer without mentioning hops and you can’t even have an entry level conversation about craft beer without mentioning them. Hops are a huge part of the craft beer scene and for many folks, the primary ingredient that got them interested in drinking craft beer. While it may be easy to describe how hops smell and taste, truly measuring how “hoppy” a beer is requires more than just our senses. That’s where IBUs come in.
IBU stands for International Bittering (or Bitterness) Unit and is the measure of hops present in a finished beer. Technically, it’s the measurement in parts per million of how much of the hops’ alpha acids were isomerized during the boiling of the wort. Those definitely aren’t my college words. I only know those words because a very smart man, John Palmer, graduated with a degree in Metallurgic Engineering and wrote a book on brewing called “How to Brew.” In this book he lays out the science behind calculating IBUs. For all you super beer geeks out there, the formula looks something like this:
IBU = (Utilization x Ounces x AAU) / Gallons of finished beer
AAU = Weight (oz) x % Alpha Acids (whole number)
Ounces is the amount of hops being used
Utilization comes from a chart found in this link
It’s that simple!
The only thing I hate more than the secondary beer market is math, so let’s talk like humans again, shall we? Good. Let’s look at this from the brewer’s point of view first, then the consumer’s.
Here’s the simplest breakdown of brewing ever: When making beer, a brewer takes the malts and soaks them in hot water for an hour (converting starches to sugars). The brewer then takes that sugary malt water (called wort) and boils that for an hour while adding hops and any other ingredients they want. When that’s done, they cool the wort, add yeast, wait a couple weeks and then they have beer. You’ve just been scienced.
During the brewing process, it’s when they add the hops and what type of hops they add that contribute to the IBUs in a beer. The strength of hops is measured in “Alpha Acids” and the higher the alpha acid’s percentage, the more potential bitterness it has. So something like a 10% alpha acid hop will primarily be used to make the beer bitter whereas a 5% alpha acid hop will be used to add to the beer’s aroma and flavor. Furthermore, the longer the hops spend in the boiling wort, the more they experience isomerization and the more time they have to employ their bitterness. Boil a hop for 60 minutes and its flavor won’t stick around but its bitterness will be big. Boil the same hop for just the last 5 minutes of the boil and it’ll smell and taste good but won’t add much bitterness.
So what does this mean for you as a consumer? While the range for IBUs is broad, it’s easiest to think of it in terms of a scale of 1 to 100. Most people can’t taste above 100 IBUs so don’t fall for beers touting huge IBUs on the label. For example, when looking at two beers on the opposite ends of the IBU specrtum, your American Light Lagers will have IBUs as low as 8 and your Imperial IPAs can have IBUs up to 120.
Now, let’s just say you’re ordering an American IPA with 60 IBUs. Must be pretty bitter, right? Justin from Saint Brewis said so and he knows like 4 things and that’s definitely one of them. Not so fast. While IBUs can tell us the bitterness level of the hops in the beer, they don’t tell us much about the beer’s balance. We can assume that when we order a big IBU beer, it’ll be fairly hoppy but if the beer is well balanced, we may not taste it as such. A prime example is the Imperial Stout which can have 50-90 IBUs versus an American IPA which can have between 40-70 IBUs. The IPA, which on both ends of its IBU range is less than the stout, will taste more hoppy than the stout all day long because it doesn’t have the big, rich malts to balance it out.
Alright, now how does Everyman Craftdrinker use this information going forward? If you’re at a decent bar with a good craft selection or shopping for craft beer at the store, the IBUs should be displayed front and center. For some big, malty styles, the IBU level could be deceiving. However, for most beers, especially your IPAs and Pale Ales, IBUs will give you a really good idea of how bitter you can expect the beer to be.
tl;dr IBUs tell you how bitter beer is.
Additional Reading on IBUs:
John Palmer’s How to Brew: http://www.amazon.com/How-Brew-Everything-Right-First/dp/0937381888
Charlie Papazian’s The Complete Joy of Homebrewing: http://www.amazon.com/gp/product/0062215752/