Beer bitterness is quantified using International Bitterness Units (IBUs), which indicate the intensity of the beer’s bitterness. It does not measure iso-alpha acids in beer, despite what many brewers believe. However, it is generally assumed that 1 IBU is equal to 1 mg of iso-alpha acid in 1 liter of water or beer. Bitterness levels in today’s brewed beers vary significantly. American lagers from large breweries typically have an IBU range of 12 to 15, while UK ales have a range of approximately 16 to 50 IBUs.
Homebrewers and some craft brewers who lack sophisticated equipment to estimate bitterness levels have developed a system called homebrew bitterness units (HBUs) for estimating bitterness in a specific volume of beer. HBUs are essentially the same as Alpha Acid Units (AAUs). The main limitation of the HBU system is that it measures the amount of hops added to the beer, not the final product’s bitterness level.
Controlling Alpha Acid Levels in Beer
Commercial brewers measure alpha acid content in a laboratory and, after conducting several test batches in the pilot brewery, adjust the hopping rate to achieve the desired International Bitterness Units (IBUs) in the beer. To ensure consistency, large breweries purchase large quantities of hops and blend them for uniformity throughout the year. Additionally, most large breweries blend their beer to mitigate variations in bitterness from batch to batch and use hop extracts to further fine-tune the bitterness.