A kinetic study on the isomerization of hop alpha-acids |
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| Authors: | Jaskula Barbara Kafarski Pawel Aerts Guido De Cooman Luc |
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| Institution: | Laboratory of Enzyme, Fermentation and Brewing Technology, KaHo St.-Lieven, Gebroeders Desmetstraat 1, B-9000 Gent, Belgium. barbara.jaskula@kahosl.be |
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| Abstract: | In this article, a detailed study on hop alpha-acid isomerization kinetics is presented. Because of the complex wort matrix and interfering interactions occurring during real wort boiling (i.e., trub formation and alpha-acids/iso-alpha-acids complexation), this investigation on alpha-acid isomerization kinetics was performed in aqueous buffer solution as a function of time (0-90 min) and heating temperature (80-100 degrees C). Rate constants and activation energies for the formation of individual iso-alpha-acids were determined. It was found that iso-alpha-acid formation follows first-order kinetics and Arrhenius behavior. Differences in activation energies for the formation of trans- and cis-isomers were noticed, the activation energy for the formation of trans-iso-alpha-acids being approximately 9 kJmol (-1) lower. |
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