Kinetics Analysis of the Isomerization of Alpha Acids to Iso-Alpha Acids Found in Hopped Beer

This project laboratory offers undergraduate students in an undergraduate analytical chemistry course the opportunity to investigate the reaction kinetics and isomerization of the three primary alpha acids cohumulone, n-humulone, and ad-humulone commonly found in hopped beer. These acids, present in the wort, undergo isomerization at elevated temperatures during the brewing process. In this experiment, we simulated this brewing step to examine the reaction order and rate constant of the isomerization of different alpha acids in beer. High-Performance Liquid Chromatography (HPLC) coupled with UV–vis spectroscopy was utilized to measure the changes in acid concentrations and track the formation of their isomerized counterparts. Through this experiment, students not only learned about isomerization and kinetics analysis from actual lab samples they prepared but also gained practical experience in adapting a method from the literature, troubleshooting method development, and preparing a sample for HPLC analysis─skills essential for any analytical chemist.