Analysis of Deuterated Standards for Determination of Hop Content in Beer
Hop plants, humulus lupulus, are used in the beer brewing process to contribute aroma, bittering and product stability. Quantifying the bittering compounds, isomerized and oxidized humulones (iso-humulone and humulinones, respectively, and their homologs), are of importance for both quality and promotional purposes. Previous methods demonstrated ability to separate and measure the homologs (co-, ad-, and n-) of humulone, iso-humulone and humulinone species in beer samples using LC-MS and HPLC with UV detection. The measurements obtained were relative amounts and were consistent with the expected hop characteristics based on the style of beer (expected bitterness, strength of hop aroma). However, in order to quantify the species present, a stable isotope dilution mass spectrometry (SID-MS) method is being developed using deuterated iso-humulone. In SID-MS, an internal standard is introduced to a sample that varies from the target analyte in isotopic composition only. This minimizes matrix effects and differences in ionization efficiency. In this poster we illustrate the development of our work to date.