Multivariate Analysis Based on GC-MS Fingerprint and Volatile Composition for the Quality Evaluation of Pu-Erh Green Tea

Food Anal. Methods (2015) 8:321–333 DOI 10.1007/s12161-014-9900-0 Multivariate Analysis Based on GC-MS Fingerprint and Volatile Composition for the Quality Evaluation of Pu-Erh Green Tea Shi-Dong Lv & Yuan-Shuang Wu & Yu-Zhu Song & Jiang-Sheng Zhou & Ming Lian & Chen Wang & Lun Liu & Qing-Xiong Meng Received: 2 April 2014 /Accepted: 14 May 2014 /Published online: 23 May 2014 # Springer Science+Business Media New York 2014 Abstract Based on the fully automatic headspace solid- green teas. Such an approach is believed to be equally appli- phase microextraction (HS-SPME)/gas chromatography- cable to other green teas. mass spectrometry (GC-MS) and multivariate statistical methods, a novel model of identifying and evaluating the Keywords Pu-erh green tea . HS-SPME . GC-MS . quality of Yunnan Pu-erh green tea was constructed for the Fingerprint . CA . PCA first time in this work. Twelve Pu-erh green teas from 12 typical production sites of Pu-erh district in Yunnan Province and 6 regular green teas from Zhejiang, Sichuan, Anhui, Introduction Henan, Hubei, and Jiangsu provinces of China were used to construct the model. Data from 18 green tea samples by GC- Tea is one of the most pleasant and popular beverages, MS were processed with fingerprint technology and chemo- and China is one of the largest tea producers, exporters, metric methods. The GC-MS fingerprints from 12 Pu-erh and consumers in the world, contributing 35.4 % to the green teas whose correlation coefficients and congruence total global production (Serpen et al. 2012). In China, tea coefficients were over 0.850 and demonstrated Pu-erh green can be classified into six different types based on different tea samples from different production sites in Yunnan were processing methods employed, such as white tea, green consistent to some extent in spite of slightly different chem- tea, oolong tea, black tea, yellow tea, and dark tea (Zhao ical indexes. A total of 77 volatile compounds were identified et al. 2011a). In these different types of tea, green tea is a in 18 green teas, mainly including linalool, linalool oxides, kind of non-fermented tea and represents 20 % of world phytol, caffeine, geraniol, and dihydroactinidiolide, and their consumption particularly in Asian countries like China, chemical compositions were slightly similar. Cluster analysis Korea, and Japan (Lambert and Elias 2010). Taxonomical- (CA) and principal component analysis (PCA) demonstrated ly, there are mainly two different varieties of tea, Camellia that 12 Pu-erh green teas could be clearly distinguished from sinensis var. sinensis and var. assamica. In China, the other six regular green teas according to their chemical char- Camellia sinensis var. sinensis of tea plants grow slowly acteristics. Our results thus indicate that the chromatographic and have smaller leaves; they are mainly distributed in six fingerprint combined with multivariate statistical techniques provinces: Zhejiang, Sichuan, Anhui, Henan, Hubei, and is useful for the identity and consistency evaluation of Pu-erh Jiangsu, and are generally used for producing regular green tea. On the other hand, the Camellia sinensis var. : : : : : : assamica of tea plants are faster growing and have larger S.<D. Lv Y.<S. Wu Y.<Z. Song J.<S. Zhou M. Lian C. Wang leaves, and they are mainly distributed in Pu-erh district of < * Q. X. Meng ( ) Yunnan Province, which are the best raw materials in Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming 650500, Yunnan, People’s manufacturing Pu-erh green tea (Hu et al. 2009; Zhao Republic of China et al. 2011b). e-mail: [email protected] Pu-erh green tea is an agricultural product of geographical indication, and production regions are protected by the L. Liu ’ Puer Tea Bureau of Yunnan Province, Puer, Yunnan 665000, People s Government of Yunnan Province. Based on this People’sRepublicofChina rule, only those products processed in the specific areas 322 Food Anal. Methods (2015) 8:321–333 could be called Pu-erh green tea. Part of the Pu-erh green tea Gas chromatography-mass spectrometry (GC-MS) is of- is further used to produce Pu-erh ripe tea (a kind of micro- ten employed to investigate changes in tea volatiles because bial post-fermentation tea), and its quality mostly depends of its reproducibility, broad dynamic range, and high accu- on the choice of raw materials and processing methods of racy; meanwhile, GC-MS workstation system can be used Pu-erh green tea. Nowadays, Pu-erh green tea has gained for convenient qualitative and quantitative analysis of vola- high popularity with potential biological and medicinal ben- tile compounds based on the standard mass spectral library efits, such as anticancer, hypolipidemic, antioxidant, and and retention index (Liu et al. 2014;Yangetal.2014; Yang eliminates effectively oxygen free radical, etc. (Du et al. et al. 2013a). As a sample preparation technique, headspace 2012; Kuo et al. 2004). solid phase microextraction (HS-SPME) has been widely Because the processing methods of green tea is almost used for extracting aroma compounds in various foods be- the same, namely, withering, pan firing, rolling, and drying, cause it takes less time and greater selectivity and is always so these green teas from different production areas or plant used with GC-MS (Arisseto et al. 2013;Yeetal.2012). CA varieties may have same appearance, aroma, or flavor and PCA as promising and useful methods also have been characteristics, which make them quite difficult to differen- widely adopted to analyze aroma components of different tiate. In recent years, the prices of Pu-erh green tea have foods and medicines, such as tallow (Song et al. 2013), shot skyward, and due to high added value of Pu-erh green vinegar (Cirlini et al. 2011), and Acorus species (Lee et al. teas, the authenticity identification of Pu-erh green tea is 2013). Up to now, there are only some publications that very important. False use of geographical origins not only discussed that quality control of Chinese Longjing green tea damages the interests of consumers, but also harms the (Song et al. 2012;Wangetal.2014) and oolong tea (Wang profits of tea producers (Huo et al. 2014). To date, the et al. 2011) involves fingerprint analysis of non-volatile identification and quality evaluation data on Pu-erh green compounds using high-performance liquid chromatography tea are extremely deficient to support its drinking and (HPLC) while there are no publications that discussed about consumption worldwide. Now, the China government has fingerprint of green tea associated with volatile components realized the importance of authenticity identification of Pu- by GC-MS. Therefore, it is very necessary to develop a erh green tea and is searching for new methods to solve comprehensive strategy to deal with chromatographic finger- this problem. So far, the quality of tea is still evaluated by prints of green tea by combination of GC-MS and multivar- traditional sensory evaluation method (Jumtee et al. 2011). iate chemometric methods. However, this approach is a complicated work and long In previous study (Lv et al. 2014a), HS-SPME/GC-MS experiences, and time is required for completing it combined with chemometric methods has been used to (Pongsuwan et al. 2006). Therefore, evaluating tea quality distinguish Pu-erh ripe tea from Fuzhuan dark tea. Al- by employing a high reproducible instrumental would be though a good distinction model has been established, popular and advantageous. Fingerprint technique has re- previous study only involved the chemometric methods, cently been widely used as an important approach for the so the obtained results are correspondingly short of some quality evaluation and control of traditional Chinese medi- comparability with fingerprint analysis technology. In the cine (TCM; Yi et al. 2009). It emphasizes a systematic current work, fully automatic HS-SPME coupled with GC- “fingerprint” characterization of analytic target that contains MS was used to construct characteristic fingerprint of Pu- a large number of information possible and relates to the erh green tea for the first time; CA and PCA technology classification of samples based on integral chemical back- coupled with GC-MS fingerprint data were used to further ground rather than characterizing a limited number of indi- evaluate the similarity and differences between the sam- vidual components (Pongsuwan et al. 2008). However, ples. The objective of the present study was to establish fingerprint technologies contain only limited information. characteristic fingerprint of Pu-erh green tea and provide a In some situations, the limited fingerprint information may reliable and efficient methodology for quality control of not be enough to reflect the comprehensive quality charac- green tea. teristics of some extremely complex samples, such as tea and TCM, so some fine distinctions between very similar chromatograms might be missed (Peng et al. 2011). There- Materials and Methods fore, some multivariate statistical methods, such as principal component analysis (PCA) and cluster analysis (CA) Materials have been proposed as proper tools to solve chromatographic problems and extract maximum useful information Twelve Pu-erh green teas were collected from 12 typical Pu- from the chromatographic fingerprints and thus improve the erh tea production sites in Pu-erh district of Yunnan Province accuracy of results (Hakimzadeh et al. 2014; Ma et al. and numbered as 1–12. In addition, regular green teas from 2013;Songetal.2012;Wuetal.2013). six different provinces numbered as 13–18 were collected Food Anal. Methods (2015) 8:321–333 323 from Zhejiang, Sichuan, Henan, Anhui, Hubei and Jiangsu immediately analyzed by GC-MS. After adsorption, SPME provinces, respectively, and used as controls compared with coating fiber was transferred to GC injection port at Pu-erh green teas. All 18 green teas were processed in 2013 250 °C for 30 min.

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