HPLC Analysis of α- and β-Acids in Hops

Abstract

Hops have been used for centuries to impart aroma and bitterness to beer. The cones of the female hop plant contain both essential oils, which include many of the fragrant components of hops, and a collection of compounds known as α- and β-acids that are the precursors to bittering agents. In order for brewers to predict the ultimate bitterness of a brewed product, it is important to have an accurate assessment of the α- and β-acid content of the hops. A high-performance liquid chromatography method is described here for the quantitation of the predominant α-acids (humulone, cohumulone, and adhumulone) and β-acids (lupulone, colupulone, and adlupulone) present in hops. Additional laboratory projects are suggested that allow students to explore various aspects of method assessment and validation.

Using a Flatbed Scanner and Automated Digital Image Analysis To Determine the Total Phenolic Content in Beer

“…Beer has an important economic value, and it is suitable for study in chemistry classes, in both theoretical and experimental work . Thus, the determination of the total phenolic content in beer samples offers an addition to already-existing laboratory experiments dealing with beer and brewing. − …”

Quantification of α-Acids in Fresh Hops by Reverse-Phase High-Performance Liquid Chromatography

“…Previous methods, such as Hops 14 5 from the ASBC and HPLC analysis of α- and β-acids in Hops from the Journal of Chemical Education, 6 focus on analyzing processed hops in a pelletized matrix. With this method, fresh hops can be analyzed and the moisture content can be used to quantify the acids as well as predict concentrations after processing.…”

“…The focus of this publication is to describe a method for the quantification of α-acids (cohumulone, humulone, and adhumulone) in freshly harvested hops by reverse-phase high-performance liquid chromatography (HPLC), utilizing ultraviolet detection and an external standard. This method advances previously described methods , by considering the unique composition of fresh hops, implementing a system of quality checks, maintaining chromatographic separation while reducing the retention range, and reducing solvent consumption. Also, common problems an analyst may encounter with suggested solutions are communicated throughout this publication.…”

Analysis of Ethanol in Beer Using Gas Chromatography: A Side-by-Side Comparison of Calibration Methods

“…For the laboratory activity described here, beer was chosen as the complex chemical mixture to be analyzed, as most college students are familiar with and/or interested in beer. Indeed, a number of classroom and laboratory activities that focus on beer and brewing have been developed recently. − This experiment focused specifically on the determination of ethanol in a commercial beer sample using gas chromatography. Each class section performed four different methods of calibration (one calibration per group), and students used pooled data to calculate the ethanol concentration in the provided beer sample, for comparison to the labeled concentration and instructor data.…”