Stepwise Identification of Six Tea ( Camellia sinensis (L.)) Categories Based on Catechins, Caffeine, and Theanine Conte
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Stepwise Identification of Six Tea (Camellia sinensis (L.)) Categories Based on Catechins, Caffeine, and Theanine Contents Combined with Fisher Discriminant Analysis Jingming Ning 1 & Daxiang Li 1 & Xianjingli Luo 1 & Ding Ding 1 & Yasai Song 1 & Zhengzhu Zhang 1 & Xiaochun Wan 1
Received: 17 December 2015 / Accepted: 19 April 2016 # Springer Science+Business Media New York 2016
Abstract Six tea types were stepwise discriminated based on their catechins, caffeine, and theanine contents of total 436 tea samples collected worldwide, combined with Fisher classification pattern recognition. Those tea samples of six types (green, white, yellow, oolong, black, and dark teas) of commonly consumed teas with different processing methods were analyzed in this work. Five main catechins ((−)-epigallocatechin gallate (EGCG), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), (−)-epicatechin (EC), and (+)-catechin (C)), caffeine, and theanine contents were accurately measured by high-performance liquid chromatography (HPLC). As a novel approach, stepwise identification combined with Fisher discriminant analysis was applied to develop an identification model. Several parameters, including model component factors, were optimized by cross-validation. The optimal Fisher model was achieved with caffeine, total catechins, theanine, theanine × theanine, EGCG/total catechins, and theanine × caffeine as component factors. The discrimination rates of black, dark, white, oolong, yellow, and green teas were 95.90, 100.00, 97.40, 95.70, 91.80, and 88.30 %, respectively. Compared with other pattern recognition approaches, the Fisher algorithm exhibited excellent performance in the final identification. The overall results show that this method is suitable to stepwise identify six tea categories, according to the measurements of main chemicals with catechins, caffeine, and theanine by HPLC and followed by the Fisher pattern recognition. Jingming Ning and Daxiang Li contributed equally to this work. * Xiaochun Wan [email protected] 1
State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 230036 Hefei, People’s Republic of China
Keywords Stepwise . Classification of tea categories . Chemical components . Fisher
Introduction Tea (Camellia sinensis (L.)) is one of the three most popular beverages worldwide due to its beneficial health properties (Yang et al. 2002). Over two billion people in more than 125 countries have habits of drinking tea (Mei 2015). Teas have been typically classified according to processing technology, which produces different characteristics and fermentation (oxidation) degrees. According to various manufacturing processes and fermentation degrees, teas can be classified into six main categories: unfermented green tea (GT), slightly fermented white tea (WT), partly fermented yellow tea (YT), semi-fermented oolong tea (OT), fully fermented black tea (BT), and post-fermented dark tea (DT). Usually, total catechin contents of the different category teas were 11.21 g/ 100 g, 5.93
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