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Thursday, September 09, 2010

How Accurate Are IBU Figures?

You're in a pub looking at a beer menu. The publican has very thoughtfully given you some data on the beers he serves, including bitterness units and alcohol percentage. If you are an average beer geek, that IBU number is going to attract your eye, and you may choose the beer with the highest number. But does it mean anything?

Let's start with the process of bittering a beer. Hops are used to balance the natural sweetness that comes from fermenting sweet wort. They add bitterness, flavor, and aroma. The bittering agents in hops are known collectively as alpha acids, but in order to make a beer taste bitter, they need to go through a chemical change known as isomerization, which happens during the boil. The amount of alpha acids a hop contains (1%-20%) and the length of time hops are exposed to boiling wort determine how many "bitterness units" a beer contains (IBU stands for "international bittering unit"). Other factors affect the perception of bitterness, like the strength of the beer and the level of carbonation; 50 IBUs will leave a barleywine tasting sweet but make a pale ale puckeringly sharp.

Okay, now back to the pub. Brewers almost always calculate their beers' bitterness. Larger breweries with labs just run a chemical test on their beer. The results they get are measures of actual acids dissolved in the beer. Small breweries, lacking a lab, have to do it mathematically. Computer programs take the several variables (alpha acid content, length of time in the boil, type of hop product) and calculate an expected IBU. In my experience, these nearly always overestimate the actual bitterness a beer will have. This is especially (but not always) true when a beer is listed at having extravagant bitterness. Many times I've tried a beer that is supposed to be in the 80s or 90s and found it light and approachable. My theory is that these programs tend to over-attribute alpha contributions by later additions, so if a brewery puts in loads of hops between 30 minutes and the end of the boil, it will inflate the IBU number, but add little bitterness. (Holler if you have a better theory.)

Given how many people base so much of their decision on the IBU figure, this is worse than a shame--it's a bit of a catastrophe. Hops are misunderstood enough already. Many people like "hoppy" beers, but are at a loss to distinguish between hop flavor and pure bitterness. IBUs only measure bitterness, and are no guide to flavor and aroma. I suspect the average drinker also doesn't know that IBUs are a chemical measure, not a guide to perceived bitterness. So I wonder--does the thoughtful impulse to include IBUs actually confuse people more than it helps?


  1. I will totally admit to being a beer lover who knows very little about beer.

    I also seldom choose my beer based on IBUs or ABV. I love a good, hoppy beer, but my number one selection factor when selecting an unfamiliar beer from a new location?

    The name. Okay - and the description. But I love funny beer names. Leafer Madness was awesome. :)

    Thanks for this, though! I knew that IBUs measured bitterness, but didn't realize that wasn't necessarily related to taste. (Someday I will be an aficionado & not just an appreciator.)

  2. There is always that "oh no no, that beer is over 6% abv, I will not touch it" especially with those not used to craft beer. The numbers, as you mentioned, are varied so much that its tough to know whats accurate.

    I shy away from basing my decision off IBUs or ABV, I am an adventurous beer drinker and would rather my pallete be the judge of what I like. Great post!

  3. I rarely brew a beer over 40 IBU, so I don't have much input. I'm not a big fan of really sharp bitterness which I find in a lot of IPAs and IIPAs I try. It's the few that utilize the late hop additions that stand out.

    I'll say that I did get to try a bottle of the Mikkeller 1000 IBU beer, going in knowing that it was pretty much impossible to achieve that figure. The resulting beer had much less perceived bitterness then many of the sharp hop bombs we get here, tasting more of liquid pine resin.

  4. The brewpubs will overestimate the IBUs so that they can get the people to say "wow, that is really hoppy". As a "hop-head" i hate the word "hoppy". There is such a huge difference between a super bitter beer and another that is dominated by the piney/resiny or even the citrusy hop flavors.

  5. Funny, I use the IBUs of a beer to determine which beer I'm going to drink, but in the opposite direction. I hate bitter beers. 50 IBU is usually my general cutoff, though I'll try something a little higher if the beer seems really interesting (HUB's DOA, for example).

  6. The most interesting fact I've learned about IBUs is that the upper range for the human palate to perceive bitterness is about 80 IBUs or so.

    So if you have a beer will an actual (as opposed to calculated) IBU value above that, you won't be able to taste the difference...

  7. There is a beer leaderboard in the Cafe and in the Bar which list the beers in both sections ordered by increasing IBU. %ABV is reported; a description of reported aromas and tastes is included.

    We believe this helps the consumer make an informed choice; which in turn facilitates consumer satisfaction.

    It is frequently difficult to find the IBU values. %ABV must be required since it is almost always reported. Only about half the brewing company bother to reply to an email inquiry.

    A regular customer and beer aficionado advocates a consumer effort [think HPP] to require breweries to report the IBU of each product. We support the idea. . . . Knowledge => power.

  8. I have read blog post postulating that the ratio of IBU to Original Gravity [IBU:OG] provides a meaning measure of perceived bitterness. I have not tested the hypothesis.

    And you?

  9. Do I sense an 'Honest IBU' project? ;)

    I think it's all a load of hogwash... and just another marketing strategy. One way craft brewers pulled people away from the BMC crowd is with excessive hops. With many, hops seem to be more important that body, flavor, and character.. depth in all flavors.

    There is no really good standard way of measuring IBU's.. other than with my tongue, and yours. And still we will all have different figures.

    'Hop Stoopid' for instance claims over '100' IBU's... yet I find Rogues 'OREgasmic' to be much much more bitter with early boil hops. I don't get bitterness from Hop Stoopid.. I get aroma and sweetness. Anchor steamer is another I find higher on the bitter scale.. or better yet, Stone's IPA... that is what I call bitter and 100+ IBU's.

    I would prefer the whole rating and printing on labels be dropped completely.

  10. Other than IBU value printed on the label how does a consumer knowingly choose between:
    - Bear Republic-Double Red Rocket Ale; 115+ IBUs / 9.2% ABV; a Big NW Red Ale
    - Bear Republic-Red Rocket Ale; 67 IBUs / 6.8% ABV; a bastardized Scottish style red ale
    - Bear Republic-El Oso; 18 IBUs / 4.5% ABV; an American Amber Ale ?

    I do not want to depend on the beer's given name. And, you?