Department of Food Science, Purdue University, 745 Agriculture Mall Drive, West Lafayette, Indiana 47907, USA.
J Agric Food Chem. 2011 Jun 8;59(11):6082-90. doi: 10.1021/jf200203n. Epub 2011 May 10.
The stability of catechins in green tea powders is important for product shelf life and delivering health benefits. Most published kinetic studies of catechin degradation have been conducted with dilute solutions and, therefore, are limited in applicability to powder systems. In this study, spray-dried green tea extract powders were stored under various relative humidity (RH) (43-97%) and temperature (25-60 °C) conditions for up to 16 weeks. High-performance liquid chromatography (HPLC) was used to determine catechin contents. Catechin degradation kinetics were affected by RH and temperature, but temperature was the dominant factor. Kinetic models as functions of RH and temperature for the individual 2,3-cis-configured catechins (EGCG, EGC, ECG, and EC) were established. The reaction rate constants of catechin degradation also followed the Williams-Landel-Ferry (WLF) relationship. This study provides a powerful prediction approach for the shelf life of green tea powder and highlights the importance of glass transition in solid state kinetics studies.
绿茶粉中儿茶素的稳定性对于产品保质期和发挥健康功效很重要。大多数儿茶素降解的已发表动力学研究都是在稀溶液中进行的，因此在适用性上受到限制，无法应用于粉末体系。在这项研究中，喷雾干燥的绿茶提取物粉末在不同相对湿度（RH）（43-97%）和温度（25-60°C）条件下储存长达 16 周。高效液相色谱（HPLC）用于测定儿茶素含量。儿茶素降解动力学受 RH 和温度的影响，但温度是主要因素。建立了各 2,3-顺式构型儿茶素（EGCG、EGC、ECG 和 EC）作为 RH 和温度函数的动力学模型。儿茶素降解的反应速率常数也遵循威廉姆斯-兰德尔-费里（WLF）关系。本研究为绿茶粉的保质期提供了一种强大的预测方法，并强调了玻璃化转变在固态动力学研究中的重要性。
