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Degradation Kinetics of Catechins in Green Tea Powder: Effects of Temperature and Relative Humidity

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Na Li†, Lynne S. Taylor‡, and Lisa J. Mauer*†

^† Department of Food Science, Purdue University, 745 Agriculture Mall Drive, West Lafayette, Indiana 47907, United States

^‡ Department of Industrial and Physical Pharmacy, Purdue University, 575 Stadium Mall Drive, West Lafayette, Indiana 47907, United States

J. Agric. Food Chem., 2011, 59 (11), pp 6082–6090

DOI: 10.1021/jf200203n

Publication Date (Web): April 17, 2011

*Phone: (765) 494-9111. Fax: (765) 494-7953. E-mail: mauer@purdue.edu.

Section:

Food and Feed Chemistry

Abstract

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.