In this article, a detailed study on hop R-acid isomerization kinetics is presented. Because of the complex wort matrix and interfering interactions occurring during real wort boiling (i.e., trub formation and R-acids/iso-R-acids complexation), this investigation on R-acid isomerization kinetics was performed in aqueous buffer solution as a function of time (0-90 min) and heating temperature (80-100 °C).
Rate constants and activation energies for the formation of individual iso-R-acids were
determined.
It was found that iso-R-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-R-acids being approximately 9 kJmol-1 lower.