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MBAA TQ http://dx.doi.org/10.1094/TQ-54-3-0806-01  |  VIEW ARTICLE
A Look at Isomerization Reduction Due to Altitude

John Palmer. MBAA Publications Director.

Abstract
Hop bitterness in beer is predominately due to the isomerization of hop α-acids during the boil, although there are other contributions to bitterness as well, such as humulinones and hulupones. A model, first published in 2005 by Malowicki and Shellhammer, indicates that isomerization rate with respect to time is solely dependent upon temperature. This paper makes use of that model to estimate the decrease in isomerization rate that can be expected when brewing at higher altitudes due to the decrease in the boiling point of water resulting from reduced atmospheric pressure.

Keywords: α-Acids, Isomerization, High altitude