IBU Beer Bitterness Test - UV Vis Spectroscopy

The bitterness of beer is an important parameter measured in the beer production process as it has a significant impact on the final taste outcome. To find out more about how the IBU of beer samples are determined spectroscopically, proceed to download the application note below.

What causes Bitterness in Beer?

The bitter flavour of beer derives from the hops used in production. During the brewing process, alpha acids in hops are isomerized into iso-aplha acids, namely isohumulones, which are what gives beer its bitter taste.

What are IBUs?

The International Bitterness Unit (IBU), developed in association with the American Society of Brewing Chemists (ASBC), is a scale which accurately describes the bitter content of beer. It is a direct measurement of the concentration of isohumulones, the bitterness-causing chemical component of beer. The scale is given as a number, representative of the parts per million of isohumulone in the sample. A light lager beer would result in an IBU between 5 and 15, whereas a dark one would be between 18 and 25. Extremely bitter beers can return readings upwards of 100 IBUs.

The bitter taste of beer can be masked through additional flavours and malts, so the IBU value may not be totally representative of the consumer’s perceived bitterness taste.

How is the IBU determined?

Spectrophotometry is a widely used method of beer analysis because of its efficiency and convenience. Measuring the absorbance at 275nm, the wavelength at which isohumulone is most absorbant, allows for the calculation of the concentration of this chemical in a given sample, which corresponds to a number on the IBU scale. In the application note below, the UV7 Excellence Spectrophotometer is used to automatically calculate the beer IBU using a predefined method.