International Bitterness Units
Beer bitterness is expressed as International Bitterness Units (IBUs), which represent a measurement of the intensity of the bitterness of the beer. In practical terms, 1 IBU equals 1 mg/L or 1 ppm of iso-alpha acids in solution. IBU values, therefore, give useful information about a brew’s bitterness intensity. The beers brewed today show a wide range in their levels of bitterness. Lagers brewed in the United States range in bitterness from 12 to 15 IBUs for the large brewers, while United Kingdom ales range in bitterness from about 16 to 50 IBUs.
Controlling Alpha Acid Levels
Commercial brewers measure the alpha acid content in a laboratory; then, after a few test batches in the pilot brewery, they adjust the hopping rate to the International Bitterness Units (IBUs) desired in the beer. To ensure consistency, large brewers purchase huge lots of hops and blend for uniform consistency throughout the year.
Click on the following topics for more information on hops.