Original research article Improved extraction of green tea components from teabags using the microwave oven Quan V. Vuong *, Sing P. Tan, Costas E. Stathopoulos, Paul D. Roach School of Environmental and Life Sciences, University of Newcastle, Ourimbah, NSW 2258, Australia 1. Introduction Green tea (Camellia sinensis) is an abundant source of catechins, which are strong antioxidants that have been receiving consider- able interest for their potential benefits in human health and food preservation (Khan and Mukhtar, 2007; Vuong et al., 2010, 2011d). For example, the catechins have been linked with protection against cardiovascular disease (CVD) (Kuriyama, 2008). Various catechin extracts from green tea have been shown to be active in humans; they lower low density lipoprotein (LDL) cholesterol, one of the major risk factors for CVD (Zheng et al., 2011). Other studies have shown that the mechanisms of actions for their cholesterol- lowering effect include an increase in the LDL receptor and a decrease in cholesterol synthesis (Bursill et al., 2001, 2007; Bursill and Roach, 2006, 2007). Therefore, due to the potential benefits of the green tea catechins, several studies have been done on the various brewing conditions to maximise the extraction of these components from green tea. The results have defined optimal water brewing conditions including the temperature being maintained at 80 8C for 30 min and a ratio of tea to water of 1:20 g/mL (Komes et al., 2010; Lin et al., 2008; Peterson et al., 2005; Vuong et al., 2011b). However, these optimisation studies focused on loose-leaf green tea and were carried out under laboratory conditions. These conditions are very different from household brewing habits, where tea is simply brewed in boiled water and left at room temperature for a short time (3 min) before being consumed (Astill et al., 2001). Although many people still traditionally prepare their green tea by brewing loose-leaf tea in boiled water, a more popular and convenient way of preparing green tea now is simply brewing a teabag in boiled water for 3 min, as suggested by the teabag manufacturers (Astill et al., 2001). However, compared to 30 min under optimal laboratory conditions, it was hypothesised that most of the catechins would not have time to infuse into the hot water during the short suggested brewing time of 3 min. This could be relevant because it may explain why results from epidemiologi- cal studies have shown that only high volumes (5–10 cups/day) of green tea are associated with health benefits (Kuriyama, 2008; Ui et al., 2009). In other words, consumers may not get the full health benefits of drinking green tea because the extraction of the catechins is not optimal under household brewing conditions. Journal of Food Composition and Analysis 27 (2012) 95–101 A R T I C L E I N F O Article history: Received 7 March 2012 Received in revised form 28 May 2012 Accepted 2 June 2012 Keywords: Bioactive non-nutrients Caffeine Camellia sinensis Catechins Food analysis Food composition Food processing Green tea Hot water extraction Microwave assisted extraction Teabag Theanine A B S T R A C T The green tea (Camellia sinensis) catechins are strong antioxidants linked with potential health benefits. Based on previous studies, it was hypothesised that the typical household conditions for brewing green tea in a teabag – 200 mL freshly boiled water for 2–3 min, as per the manufacturers’ instructions – were not sufficient to extract all the catechins and that a household microwave oven could be used to improve the extraction. The catechins and the two other main green tea components, caffeine and theanine, were monitored by HPLC. The typical household conditions only extracted 62% (61 mg/g tea), 76% (24 mg/g) and 80% (10 mg/g) of the catechins, caffeine and theanine, respectively, from the five varieties of teabags analysed. However, using microwave assisted extraction (MAE) by first brewing a teabag in 200 mL freshly boiled water for 0.5 min before irradiation for 1 min in a microwave oven (hot MAE), improved the extraction of the catechins and caffeine to 80% (80 mg/g) and 92% (29 mg/g), respectively, although the extraction of theanine was not affected. Therefore, the hot MAE technique could help maximise the extraction of the catechins for those who consume green tea for the potential health benefits of the catechins. ß 2012 Elsevier Inc. All rights reserved. * Corresponding author. Tel.: +61 2 4348 4129; fax: +61 2 4348 4145. E-mail address: van.vuong@uon.edu.au (Q.V. Vuong). Contents lists available at SciVerse ScienceDirect Journal of Food Composition and Analysis jo u rn al ho m epag e: ww w.els evier .c om /lo cat e/jfc a 0889-1575/$ – see front matter ß 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jfca.2012.06.001