Direct Quantitation of Hops Bittering Compounds by Electrospray Ionization Mass Spectrometry

Date of Award


Degree Name

Master of Science



First Advisor

Andre Venter, Ph.D.

Second Advisor

John Miller, Ph.D.

Third Advisor

Ramakrishna Guda, Ph.D.


Electrospray ionization mass spectrometry (ESI-MS), hops, ion suppression, rapid quantitation, systematic optimization, α-acids and β-acids

Access Setting

Masters Thesis-Abstract Only

Restricted to Campus until



Hops are one of the key ingredients in beer production as they impart the characteristic bitterness in beer and are the source of flavor and aroma. The hop bittering compounds are mainly α-acids and β-acids that directly impact the taste of the beer. Therefore, quantitating α -acids and β-acids is crucial as they predict a particular beer's bitterness and taste profile. An efficient analytical method is consequently desirable to determine the acid content in hop products for quality control. The existing methods used to quantify hops share limitations such as lengthy analysis time and labor intensiveness. HPLC-UV is the standard method in the industry due to its ability to determine individual congeners of α-acids and β-acids. However, the lengthy analysis times of up to 30 minutes is a significant problem associated with the HPLC determination of hop acids.

In this research, we have developed a rapid, efficient, and greener method for quantitating α-acids and β-acids by electrospray ionization mass spectrometry (ESI-MS) without chromatographic separation. Our new ESI-MS method accurately quantifies the α-acids and β- acids in under one minute. The matrix effect (mostly ion suppression of α -acids) was assessed as part of method validation, and relevant measures were taken to minimize such impacts. The optimization of instrument and solvent conditions led to the significant reduction of ion suppression of α-acids from over 30% to below 10%, hence ensuring the accuracy of the method.

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