title: A kinetic study on the isomerization of hop alpha-acids.
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.
authors.affiliation: Laboratory of Enzyme, Fermentation and Brewing Technology, KaHo St.-Lieven, Gebroeders Desmetstraat 1, B-9000 Gent, Belgium. barbara.jaskula@kahosl.be
authors.forename: Barbara
authors.initials: B
authors.lastname: Jaskula
authors.forename: Pawel
authors.initials: P
authors.lastname: Kafarski
authors.forename: Guido
authors.initials: G
authors.lastname: Aerts
authors.forename: Luc
authors.initials: L
authors.lastname: De Cooman
mesh_terms: D053138:Cyclohexenes / Q000032:analysis / Q000737:chemistry*; D006358:Hot Temperature; D027582:Humulus / Q000737:chemistry*; D007536:Isomerism; D007700:Kinetics; D012996:Solutions; D013729:Terpenes / Q000032:analysis / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D053138:Cyclohexenes; D012996:Solutions; D013729:Terpenes; C007966:humulon