G. HASMAN (1), A. R. Venter (1); (1) Western Michigan University, Kalamazoo, MI, U.S.A.
Poster
The alpha- and beta-acid contents in hops have a direct impact on the
taste of beer and are important quality control measures. Hop acids are
usually quantified by HPLC-UV, UV-Vis alone, or potentiometric methods.
The HPLC-UV method (ASBC Hops-14) is generally preferred by the brewing
industry for improved accuracy over other methods. This method also
provides information on the relative concentrations of the different
congeners that are present in both alpha and beta classes of hop acids.
However the HPLC-UV analysis can take between 10 and 60 min to complete.
UV-Vis methods (e.g. Hops-6a) yield only the total alpha- and beta-acid
contents. Here, we present an alternative method for hop-acid
quantification that provides analysis of adhumulone, cohumulone,
adlupulone, and colupulone with cycle times of less than 1 min/sample.
Ion suppression during electrospray ionization is usually avoided during
LC-MS analysis by separation of the species in solution prior to
ionization. We show that ion suppression does not negatively impact the
results obtained by direct analysis across a concentration range of 0.1
to 5 µM for each hop acid. Statistically similar data were obtained by
external calibration when the same sample sets were analyzed with and
without chromatographic separation prior to mass spectrometric analysis.
Chromatographic separation prior to mass spectrometry analysis is not
required to quantitate the alpha- and beta-acid contents in hops. The
new direct analysis mass spectrometric method was further validated by a
comparison of quantitation results obtained for various ASBC Check
Sample Service samples analyzed by standard methods. Statistically
equivalent results were obtained for various sample types such as
bracts, pellets, powders, and extracts.
Gregg Hasman, Jr. studied chemistry at Michigan Technological
University (Houghton), where he received his B.S. degree in chemistry in
2011. He taught Studio Chemistry Lab I and II courses at Michigan
Technological University from 2010 to 2012 under the guidance of Paul
Charlesworth. Gregg is currently in his second year of the analytical
chemistry Ph.D. program at Western Michigan University (Kalamazoo)
studying under Andre Venter. In mid-2013, Gregg supervised the startup
of the hops testing facility at Western Michigan University, which
offers standardized hop analysis performed according to the official
methods of analysis of the American Society of Brewing Chemists. Gregg’s
current research involves the development of a novel method of hop
analysis using paper spray ionization mass spectrometry to rapidly
quantitate the alpha and beta content in hops, as well as identify
characteristic components within various breeds of hops.
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