<P> The International Bittering Units scale , or simply IBU scale , is used to approximately quantify the bitterness of beer . This scale is not measured on the perceived bitterness of the beer , but rather the amount of iso - alpha acids . There are several methods to measure IBU . The most common and widely used way is through spectrophotometry . In this process , hops are boiled in wort to promote isomerization . Since the iso - alpha acids are slightly hydrophobic , a reduction of the pH by adding acid increases the hydrophobicity of the iso - alpha acids . At this point , an organic solution is added and the iso - alpha acids shift to the organic layer out of the aqueous wort . This new solution is then placed in a spectrophotometer and the absorbance is read at 275 nm . At this wavelength , the iso - alpha acids have their highest absorbance which allows for the calculation of the concentration of these bittering molecules . This technique was adopted at the same time as another method based on measuring the concentration ( in milligrams per litre ; parts per million w / v ) of isomerized α acids ( IAA ) in a beer , causing some confusion among small - scale brewers . The American Society of Brewing Chemists , in the introduction to its methods on measuring bitterness , points out some differences between the results of the two methods : </P>
<P> The International Bittering Units scale , or simply IBU scale , is used to approximately quantify the bitterness of beer . This scale is not measured on the perceived bitterness of the beer , but rather the amount of iso - alpha acids . There are several methods to measure IBU . The most common and widely used way is through spectrophotometry . In this process , hops are boiled in wort to promote isomerization . Since the iso - alpha acids are slightly hydrophobic , a reduction of the pH by adding acid increases the hydrophobicity of the iso - alpha acids . At this point , an organic solution is added and the iso - alpha acids shift to the organic layer out of the aqueous wort . This new solution is then placed in a spectrophotometer and the absorbance is read at 275 nm . At this wavelength , the iso - alpha acids have their highest absorbance which allows for the calculation of the concentration of these bittering molecules . This technique was adopted at the same time as another method based on measuring the concentration ( in milligrams per litre ; parts per million w / v ) of isomerized α acids ( IAA ) in a beer , causing some confusion among small - scale brewers . The American Society of Brewing Chemists , in the introduction to its methods on measuring bitterness , points out some differences between the results of the two methods : </P>
what does ibu stand for in beer making
what does ibu stand for in beer making
International Bittering Units
International Bittering Units