T. D’ANDREA (1); (1) Colorado Mesa University, Grand Junction, CO, U.S.A.
Poster
Hops have long been used in the brewing of beer and play several vital
roles in the process. One significant role is the contribution of
bitterness to a beer. The bitterness from hops is largely due to the
formation of iso-alpha-acids in boiling wort. Due to the importance of
iso-alpha-acid formation in wort, the kinetics of isomerization have
been extensively studied by several groups. While iso-alpha-acids impart
desirable flavors in a finished beer, it is also known that
iso-alpha-acids degrade due to light exposure to produce unfavorable
components. For example, iso-alpha-acids absorb UV light and initiate a
series of chemical reactions ultimately leading to the formation of
3-methyl-2-butene thiol, which has a strong “skunky” aroma.
Iso-alpha-acids are also susceptible to thermal degradation. Even in the
absence of light, iso-alpha-acids can decompose over time, which
affects the flavor and overall quality of beer. As a result, our
research group has been studying the thermal degradation of
iso-alpha-acids. Specifically, we have been using high-performance
liquid chromatography and 4-tert butyl phenol as an internal standard to
monitor the concentration of iso-humulone, iso-cohumulone, and
iso-adhumulone as a function of time and temperature. The degradation of
these compounds follows first-order kinetics, and rate constants for
the degradation are currently being measured at several temperatures.
These experiments will allow for the determination of an activation
energy for thermal decomposition of iso-alpha-acids, which will give
valuable insight into the ever-changing chemical composition of an aging
beer.
Tim D’Andrea received his B.S. degree in chemistry from Ursinus
College in 2003. He went on to the University of Colorado, Boulder, from
which he received his Ph.D. degree in physical chemistry in 2008. Since
2008, Tim has been employed at Colorado Mesa University in Grand
Junction, where he is currently an assistant professor of analytical
chemistry.
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