“We people, especially the betting kind, are in to stats. It helps us organize an otherwise open playing field. Knowing which horse to put our money on, what level hotness we want our pad Thai to be, which side of the coin is likely to come up when we trust our luck to the flip. It is in this desire to organize the world around us that the powers that be in Brewing Science came up with IBU’s (International Bittering Units). To put it simply, 1 IBU is 1 milligram of iso-alpha-acid (which is solubilized alpha-acid, the main bettering component of hops) per liter. Simple enough, right? I’ll try not to get too math-classy about it, but to break it down a little bit:
Say you have a hop, oh… Nugget, for example. A classic bittering hop. And you know it is 8% alpha acid since your hop dealer told you so, who was him/herself told this to be so by a lab which analyzed the hops fresh from the field. You now know that 8% of the total weight of that hop is potential bitterness. But, the thing that works against you is that theoretically you can only get about 30% of that 8% to solubilize in the boil which you may or may not actually know the volume of. And to further complicate the numbers, a considerable amount of these iso-alpha-acids that make up the bitterness are lost during fermentation due to carbonation stripping the components out of solution, and flocculation of the yeast grabbing some for itself on the way down (theoretically, anyway). When you condition the beer in the tank before you put it in kegs, you lose a little there as well. And none of this accounts for aroma (we’ll talk about that next week), or degradation over time in the keg.
Let’s slow down little, check back in. We got out our trusty calculator and figured out that our beer would have 120 IBU’s in it (we want to make a face-melting super-hopped IPA, of course). But, since we will lose some of these bittering units in the fermentation and conditioning, how reliable is that number? An additional factor is that other components of hops add bitterness via different chemical reactions that have nothing to do with iso-alpha-acid at all. So…. Do we have more than 120IBU’s in the end? Less??! I wonder…does it really matter!?!?
In the end, chasing these numbers should be taken for what it is. Perhaps, the intent of the brewer, or the driving force behind the marketing of a particular beverage (Dogfish head’s 120 min. IPA, for example). According to the Science people, we can only taste up to about 100IBU’s. Beyond that, it’s a waste of Hops? Or is it?! Surely it’s contributing something?! But we need expensive analyzing like Gas chromatography–mass spectrometry to measure these things, I think they mainly use Gas-Chromatograph Mass-Spectrometer to measure the contents of stardust. To run our IPA through the machine seems a bit overkill, don’t you think? In the end, does it taste good? Is the beverage well balanced and does it make your heart happy? Then its “______IBU’s” (insert your own statistic here). When you read a menu to decide what to order for dinner, you notice Chef Bob doesn’t say how many teaspoons of cumin he used. Just, that cumin is in the dish. You know what that means. You know wether you like cumin or not, which in turn helps you make an informed decision.
I think you see my point. IBU’s are not always what they seem. Take Guinness, for example. Would you call that beer hoppy? I surely wouldn’t. But what would you say if you didn’t previously know what Guiness tasted like, and you saw it on the menu coming in at 45 IBU’s. If you don’t like hoppy beers, would you even consider ordering that? I might think twice.
To summarize, don’t let the IBU’s rule your decisions. Let your tastebuds keep score and create your own stats. You’ll surely win every time."