Scott Lafontaine (1),
Tom Shellhammer (1), Philip Wietstock (2); (1) Oregon State University,
Corvallis, OR, U.S.A.; (2) Technische Universität Berlin, Berlin,
The method being presented was developed as an alternative approach
to measure iso-alpha-acids in beer using solid-phase extraction (SPE)
and subsequent spectrophotometric measurement. It was initially
conceived to be a simpler alternative to the international bitterness
unit (ASBC Beer 23a) and because it eliminates the use of iso-octane.
However, after a second ASBC Technical Subcommittee report in 2013 the
reproducibility and repeatability results of a ring study were judged to
be unacceptable, and the method needed improvement. Recent changes in
the elution solvent and the stationary phase during the SPE have
increased the reproducibility and repeatability of the proposed method.
Interestingly, the method was also expanded to include oxidized hop
acids, which have been shown to contribute sensory bitterness in
hop-forward beers. The updated SPE protocol was used to extract
isomerized and oxidized iso-alpha-acids from 120 commercially available
beers. The resulting UV absorbance for these beers were correlated to
IBUs (ASBC Beer 23a ) and iso-alpha-acids by HPLC (ASBC Beer 23e), as
well as sensory bitterness as perceived by a trained taste panel. These
results suggest that the proposed method be considered as a potentially
viable alternative approach to HPLC and the IBU for measuring isomerized
and oxidized alpha-acids in beer.
In the spring of 2015, Scott Lafontaine joined Dr. Thomas
Shellhammer’s laboratory at Oregon State University in the Department of
Food Science and Technology to pursue a Ph.D. degree in food science.
Currently, Scott’s research interests broadly revolve around hop flavor
in beer. He graduated with a M.S. degree in chemistry from Oregon State
University in the winter of 2015 and received his B.S. degree in both
chemistry and science technology from Kean University in the spring of