You might have heard the term IBU used in terms of beer. Maybe you saw it on a beer can or heard your craft beer nerd friends talking about.
But what does it actually mean?
The short answer is that IBU stands for International Bitterness Units scale (sometimes called International Bittering Units. IBU is basically a measure of how bitter a beer tastes.
How is IBU Calculated?
International Bitterness Units are a chemical measurement of how bitter a beer will taste. To get the IBU of a beer, brewers will take a chemical measurement of the proportion of polyphenols, isomerized and alpha acids and other compounds.
Where Does the Bitterness in Beer Come From?
The bitterness in beer comes from hops. Hops are added during the boiling process in brewing beer and make beer taste bitter.
As described by Allagash brewing: “Hops are the flowers, or cones, of a plant called humulus lupulus. Hops help to keep beer fresher, longer; help beer retain its head of foam—a key component of a beer’s aroma and flavor; and, of course, add “hoppy” aroma, flavor, and bitterness.”
When you boil the hops in the brewing process, it starts a chemical process called isomerization, which transforms the alpha acids to so-called isohumulone- or iso-acids. They are what gives the beer it’s bitter taste.
The IBU Scale
The IBU is a scale that measures parts per million of isohumulone (iso-acids) and other compounds found in a beer.
IBU technically goes from 0 to 120 or so, but most of the beer you’ll drink has between five IBUs and 100 IBUs. Ales tend to be higher on the IBU scale than lagers and other beers such as porters and stouts. XPAs, IPAs and double IPAs have more bitterness and therefore have a higher IBU still.
The number of IBUs in a beer does correspond pretty well to how bitter it tastes, although the malt flavor in some beers can effectively “mask” the bitterness and make the IBU scale not a true measure. But, anyway, it is the most scientific measure of bitterness in beer we have, so brewers to rely on it.
Here’s a rough guide to the typical IBU range for popular beer styles:
- American mainstream lagers: 5-10 IBUs (low IBU)
- Hefeweizens: 8-10 IBUs
- Porters: 18-35 IBUs
- Dunkels: 18-28 IBUs
- Amber lagers: 20-25 IBUs
- American Pale Ale: 35-40 IBUs
- India Pale Ale: 55-70 IBUs
- Double IPAs: 65-100 IBUs (high IBU count)
If you want to now the IBU rating for your favorite brew, visit Drizly and look up the beer and you’ll find all the IBU for most beers along with the ABV and info on how many carbs it has and how many calories.
Here is the IBU number for a range of popular beers:
- Budweiser: IBU 13
- Corona Extra IBU 18
- Bud Light IBU 10
- Heineken IBU 19
- Sierra Nevada Pale Ale IBU 38
- Lagunitas IPA 52
What is perceived bitterness?
While the proportion of bittering compounds is generally a good measure of the bitterness of the taste, it’s not quite that simple.
The more malt in a beer, the more sweet it tends to be, and the malty sweetness can balance out the bitterness. Therefore you can have a malty beer with a high IBU that tastes less bitter than a lightly malted beer with a lower IBU.
Think of it like coffee – a black coffee tastes bitter, but when you add even a little bit of sugar to it it suddenly corrects the bitterness. But on a chemical basis, the compounds that make coffee bitter are still present.
And of course all beer drinkers are diffferent and we all have different taste buds – so what tastes bitter to me may not to you, and vice versa. The human palate is a mysterious thing!
Some brewers believe that there are so many factors that affect the perceived bitterness level of a beer – such as carbonation, water chemistry, residual sugar and hop bitterness – that the IBU rating can’t be relied upon.
There view if that the IBU range, while a general guideline, doesn’t really reflect the drinking experience and isn’t a true measure of the bitterness in beer.
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