A very bitter Peter Fowler…though we’re sure the actual beer won’t look quite like this.

A UK brewer aims to claim the title of the World’s Most Bitter Beer with a beer with a beer he estimates will weigh in at 500 IBUs.

The Oxford Mail reports that Peter Fowler’s latest creation, a nine-gallon (forty litre) keg of barley wine – made using £100 ($174) worth of hops, compared to £5 for an average beer. The paper quoted Mr Fowler as saying he had not tasted it “as he may not be able to handle it.”

International Bittering Units (IBUs) are a measure of the bitterness of beer, with an IBU defined as a milligram of isomerised alpha acid per litre of beer. In his book, How to Brew, John Palmer describes the process of getting the bitterness from hops into beer in this way:

“Hop resins act like oil in water. It takes the boiling action of the wort to isomerize them, which means that the chemical structure of the alpha acid compounds is altered so that the water molecules can attach and these compounds can dissolve into the wort. The percentage of the total alpha acids that are isomerized and survive into the finished beer, i.e. utilized, is termed the “utilization”. Under homebrewing conditions, utilization generally tops out at 30%.”

John also has a good background to IBUs in this article in US homebrew magazine, Brew Your Own.

While the maximum level at which people can taste bitterness seems to run from 60 to 100 IBUs, depending on which source is quoted, and there is a theoretical maximum to the amount of alpha acid that can be isomerized in beer, brewers do seem to want to push the envelope. Peter might need to go back to the drawing board though to claim the record. Danish brewer Mikkeller claims to have brewed an experimental beer of 2007 IBUs in 2007 for the Copenhagen Beer Festival, and Mikkel has recently been forced to defend himself for announcing plans to make a beer with a theoretical hop bitterness of 1000.

The ever sensible Garrett Oliver should have the last word on this one…

“The hoppiest beer?” Garrett asked. “It’s a fairly idiotic pursuit, like a chef saying, ‘This is the saltiest dish.’ Anyone can toss hops in a pot, but can you make it beautiful?”