Thirsty Thursday - What The Hell Is An IBU

The world of beer has seen an explosion of new and unique craft beers hitting the market over the last few years.  Along with these new beer options comes a certain level of pride, sophistication and craftsmanship.  Perhaps in an attempt to better educate the drinkers or they just like to show off, but may breweries like to share the ingredients found in their beers. It has become quite common to see the variety of malts, hops, yeast and even the water sources used to make these specialty beers.  Another very common piece of information that you can find on a lot of beers these days is the IBU.  Many brewers revel in their ability to pack as many IBUs into a beer.  Craft beer drinks have learned that the more IBU the more bitter the beer, but beyond that what the hell is an IBU? 

IBU or International Bitterness Unit is a measurement used to quantify the bitterness of beer.  Since bitterness is somewhat subjective we need to drill into the more scientific reason that some beers are more bitter than others. 

During the brewing process hops are added to flavour the beer.  Hops contain two types of acids; alpha acids and beta acids.  When heated the alpha acids in the hops are isomerized (change molecular form but keep the same number of atoms) and leaves what is known as isomerized alpha acids in the beer.  These iso-alpha acids are the main source of bitterness in beer.  Different varieties of hops have different amounts of these acids so brewers can carefully select the hops to their liking.    

The hops contain beta acid as well.  These acids are harsher and more bitter then the alpha acids and generally release through the later stages of fermentation and conditioning. 

The IBU scale measures the actual amount of iso-alpha acid within a beer.  This measurement can range anywhere from only a few (3 or 4) up to over 100.  The noticeable changes in bitterness over 100 IBU is often regarded as minimal and not generally measured. 

Even with a scientific measurement of iso-alpha acid quantity in beer, there is still a subjective element to the bitterness of a beer.  Bitterness can be greatly reduced by the other flavours in a beer.  Heavily malted full body beers can tolerate a higher IBU without seeming as bitter while lighter beers with lower IBUs might pack more bitterness.  Listed below are a few common styles of beer and their average IBU measurements:

Imperial Stout – 71 IBU

American IPA – 57 IBU

American Brown Ale – 52 IBU

American Pale Ale – 39 IBU

German Pilsner – 33 IBU

Irish Red Ale – 22 IBU

Cream Ale – 18 IBU

Thanks for taking the time to read through this and I hope that you're just a little bit more informed.  Now go out and impress your friends and family with your new found knowledge of beer and IBUs!