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Four drying experiments of mate leaves (Ilex paraguariensis St. Hilaire) were carried out in a packed bed superheated steam dryer by varying outlet steam temperature from 120 to 140C and equivalent particle diameter from 4.7 ¥ 10 -3 to 6.95 ¥ 10 -3 m. The influence of these variables on the drying coefficient calculated by assuming a simplified drying kinetic model was investigated. A classical statistical approach revealed the significant effect of both factors on this parameter. Two additional drying runs were performed at identical conditions with conventional hot air and low pressure superheated steam, respectively. The influence of drying atmosphere on the total content of phenols was evaluated. A conventional process of extraction by using an aqueous methanol solution was adopted. Analyses for total phenols were performed by spectrophotometry at 715 nm by applying Folin-Denis assay. The leaves dried with superheated steam had approximately 47% higher retention of these compounds. 4 Corresponding

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.

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