Hop (Humulus lupulus) acid and metabolite profiles in craft brewing cultivars by HPLC and GC-MS analysis

There are many chemical changes that take place during wort boiling, to include the oxidation of polyphenols, production of melanoidins via Maillard reactions, protein precipitation, enzyme inactivation, and isomerization of hop acids. Hops are one of the most important raw materials used in the production of beer as it is responsible for the bitter flavor and aroma of beer. The metabolites from hops also provide beer with other qualities like flavor stability, foam stability, microbial stability, color, and mouthfeel. During the wort boiling, the α-acids are isomerized to iso-α-acids. These products can lead to various ratios of the cis/trans-iso-α-acids, which can affect the kinetics of oxidative degradation as well as the bitter taste development in the final product. Environmental changes to the terroir can lead to alterations in the acid profiles of individual hop cultivars. Here we present our initial findings of acid and metabolite profiles from hops through the brewing process at a local craft brewery using high performance liquid chromatography (HPLC) and gas chromatography – mass spectrometry (GC-MS). The potential for the metabolites to affect the foam stability are also reported.