Isohumulones highly contribute to the typical beer flavor like bitter taste with concentrations varying between 5 and 100ppm. Additionally, they have bacteriostatic properties and an important function for foam stability. Unfortunately, the isohomulones have pronounced light sensitivity, developing repulsive taste and “skunky” odor due to reactions with the sulfur-containing worth after light exposure leading to 3-methyl-2-buten-1-thiol (skunk thiol). This phenomenon is termed “lighstruck flavor”.

To prevent the development of the so-called “lightstruck flavor”, reduced isohumulones like tetrahydroisohumulones (tetrahydroiso-acids) are often used in the brewing process to enhance both the light and the foam stability of beer. In Germany, the addition of non-natural reduced isohumulones is prohibited due to the “Reinheitsgebot”, which states that only natural hop compounds are allowed in the brewing process. Because of their key role in the flavor characteristics and of the stringent quality control, it is of great interest to accurately determine and quantify isohumulones in beer.

Here, we show the analysis of different beer samples using a mobile LC solution as a robust and rugged system, resistant against shocks or vibrations during transportation. Direct injection of the beer samples and an isocratic measurement enables the user to perform super easy on-site measurement in a mobile laboratory without cumbersome sample preparation or method development. With this setup, highly precise and linear analyses were enabled for the determination and quantification of non-reduced and reduced isohumulone standards as well as for isohumulone analysis in 14 different beer samples. The international bitterness units were calculated for the tested beer samples revealing significant differences from for example Lager beer to Pils as expected. In addition, reduced isohumulones could only be detected in an American Premium Lager beer.