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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