Effects of cosolvents on the decaffeination of green tea by supercritical carbon dioxide Hyong Seok Park a , Hee Jin Lee a , Min Hye Shin a , Kwang-Won Lee a , Hojoung Lee b , Young-Suk Kim c , Kwang Ok Kim c , Kyoung Heon Kim a, * a Division of Food Bioscience and Technology, College of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Republic of Korea b Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Republic of Korea c Department of Food Science and Technology, Ewha Womans University, Seoul 120-750, Republic of Korea Received 31 January 2007; received in revised form 3 March 2007; accepted 25 April 2007 Abstract Due to the adverse effects of the caffeine in a variety of plant products, many methods have been explored for decaffeination, in efforts to remove or reduce the caffeine contained in plant materials. In this study, in order to remove caffeine from green tea (Camellia sinensis) leaves, we have employed supercritical carbon dioxide (SC–CO 2 ), which is known to be an ideal solvent, coupled with a cosolvent, such as ethanol or water. By varying the extraction conditions, changes not only in the amount of caffeine, but also in the quantities of the principal bioactive components of green tea, including catechins, such as epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin (EC), were determined. The extraction conditions, including temperature, pressure and the cosolvent used, were determined to affect the efficacy of caffeine and catechin extraction. In particular, the type and concentration of a cosolvent used constituted critical factors for the caffeine removal, combined with minimal loss of catechins, especially EGCG. When the dry green tea leaves were extracted with SC–CO 2 modified with 95% (v/v) ethanol at 7.0 g per 100 g of CO 2 at 300 bar and 70 °C for 120 min, the caffeine content in the decaffeinated green tea leaves was reduced to 2.6% of the initial content. However, after the SC–CO 2 extraction, a substantial loss of EGCG, as much as 37.8% of original content, proved unavoidable. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Supercritical carbon dioxide; Green tea; Caffeine; Catechins; Decaffeination 1. Introduction Green tea (Camellia sinensis) leaves have a long tradi- tion of being used as a drink in Asian countries, and green tea has become one of the most popular drinks in the world, owing both to its unique taste and to a variety of positive health benefits associated with the plant. Green tea is prepared via processing of the tea leaves, such as by steaming or roasting, without fermentation. When the leaves are semi-fermented or fully fermented, the products can be differentiated from green tea, and are referred to as oolong tea and black tea, respectively. The components of green tea include the catechins, caffeine, and essential oil components, and the composition of green tea varies signif- icantly with the strain of tea tree, the harvest time, and the manufacturing process employed (Chu & Juneja, 1997). The primary bioactive components of green tea are cat- echins, which are composed primarily of epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gal- late (ECG) and epicatechin (EC). These catechins are gen- erally recognized to exert desirable biological and physiological effects, including antioxidative (Cai et al., 2002; Joshi, Hasan, Chandra, Husain, & Srivastava, 2004; Liu, Ma, Zhou, Yang, & Liu, 2000), anticancer (Moyers & Kumar, 2004), anti-inflammation (Tedeschi, Suzuki, & Menegazzi, 2002; Trompezinski, Denis, Schmitt, 0308-8146/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2007.04.064 * Corresponding author. Tel.: +82 2 3290 3028; fax: +82 2 925 1970. E-mail address: khekim@korea.ac.kr (K.H. Kim). www.elsevier.com/locate/foodchem Food Chemistry 105 (2007) 1011–1017 Food Chemistry