Determination of Isoxanthohumol, Xanthohumol, Alpha and Beta Bitter Acids, and trans and cis-iso-alpha acids by HPLC with UV and Electrochemical Detection: Application to Hop and Beer Analysis

Abstract

Hops are the female flower clusters of the hop species, Humulus lupulus. They are used as a flavoring and stability agent in beer, and are also used for various purposes in other beverages and as an herbal medicine. Hops contain a number of important phytochemicals including: Xanthohumol (a prenylated chalconoid), and alpha- and beta- acids. As part of the beer brewing process hops or hop extracts are added during the boiling of the wort. The virtually insoluble alpha-acids (humulones) are isomerized into the more soluble iso-acids, the main bittering substances in beer. Beta acids (lupulones) do not isomerize and have a negligible effect on beer taste. Instead, they contribute to beer's bitter aroma but unfortunately may oxidize into compounds that can give beer off-flavors.