Chemical kinetics of 5-o-caffeoylquinic acid in superheated steam: effect of isomerization on mate (Ilex paraguariensis) manufacturing.

A set of experiments was carried out to investigate the chemical stability of 5-o-caffeoylquinic acid (5-CQA) in the presence of superheated steam. A batch cylindrical reactor made of glass and isothermally operated between 398 and 499 K was used in the experiments. A high-performance liquid chromatograph equipped with a diode array detector was applied to monitor the 5-CQA concentrations. The conversions of 5-CQA were correctly reproduced with a simplified kinetic model represented by a reversible pseudofirst-order reaction of isomerization. The effect of temperature on the forward rate constant was represented by the Arrhenius equation with parameters tuned on experimental data. The heat of isomerization of 5-CQA and the equilibrium constant at 298 K were calculated by involving the integrated form of the van't Hoff equation. The observed reaction was revealed to not be detrimental for the quality of manufactured leaves and branches of mate because the content of total chlorogenic acids was not changed.