Department of Chemical Engineering, Polytechnic Center (DTQ/ST/UFPR), Federal University of Paraná, Jardim das Américas, 81531-990, Curitiba, PR, Brazil.
J Agric Food Chem. 2009 Dec 23;57(24):11564-9. doi: 10.1021/jf903388a.
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.
进行了一组实验，以研究在过热蒸汽存在下 5-咖啡酰奎宁酸（5-CQA）的化学稳定性。实验中使用了一个由玻璃制成的间歇式圆柱形反应器，在 398 至 499 K 之间等温操作。应用配备二极管阵列检测器的高效液相色谱仪来监测 5-CQA 的浓度。通过一个简化的动力学模型，该模型代表了一个可逆的异构化拟一级反应，正确地再现了 5-CQA 的转化率。温度对正反应速率常数的影响用阿伦尼乌斯方程表示，参数通过实验数据进行调整。通过涉及范特霍夫方程的积分形式，计算了 5-CQA 的异构化热和 298 K 时的平衡常数。观察到的反应对马黛茶的叶片和枝条的质量没有不利影响，因为总绿原酸的含量没有变化。
