Analysis Of Volatile Component Of Tea Using Gas Chromatography-mass Spectrometry And Chemometric Methods

Tea is one of the most widely consumed beverages in the world. Grown in about30countries worldwide, the tea plant(Camellia sinensis L.) originated in China. In China, tea can be classified into six different types based on different processing methods employed, such as unfermented green tea, slightly fermented white tea and yellow tea, semi-fermented oolong tea, fully fermented black tea, and post fermented dark tea. As a scientific and healthy lifestyle, drinking tea has been accepted by the public. Previous studies have found that tea have many special beneficial health effects, such as hypolipidemic, anti-oxidation, anti-atherogenic, anti-cancer, and anti-aging, etc. In recent years, with the strengthening of people’s concept of health, tea is getting more favour of people. The aroma of tea is one of the most important factors for affecting the character and quality, capturing and developing the consumer loyalty and determining the price of tea. In this work, various tea samples with different types or same types which have different regions were collected from the major tea production areas in China, their comprehensive volatile compound were compared by fully automatic HS-SPME combined with GC-MS analysis and multivariate statistical analysis such as CA and PCA was also employed. The author hopes this study can provide some useful advice and reference for the great development of the tea market in our country in the future. The main research and conclusions are as follows:1. A total of50tea samples of various green, oolong, black and Pu-erh tea in China were profiled using fully automatic headspace solid-phase microextraction (HS-SPME)/gas chromatography-mass spectrometry (GC-MS) coupled with chemometric methods. A total of165volatile components were identified in50tea samples, the aroma composition and their quantities in different types of teas varied quite widely. The main kinds of aroma components in11green teas and13black teas were alcohols, hydrocarbon and ketones compounds, weheras alcohols content is higher in the black tea, may be the characteristics flavoring compositions in black tea. The alcohols, hydrocarbon and esters compounds were the major aroma components in13oolong teas, and methoxyphenolic compounds were the most abundant components in13Pu-erh teas. The CA and PCA showed four different types of teas could be partially classified using the volatile components. The differences probably are related to the producing region and processing technology of these teas.2. Thirteen Pu-erh teas and13Fuzhuan teas obtained from two different production areas in China were profiled using fully automatic HS-SPME/GC-MS coupled with chemometric methods. A total of93aroma components were identified in26dark teas, among them, methoxyphenolic compounds (31.77%) were the most abundant components in Pu-erh teas, while ketone compounds (25.42%) were the most abundant components in Fuzhuan teas. CA and PCA showed that these two types of dark teas could be clearly distinguished according to their chemical characteristics. This study suggested that the proposed strategy could provide a feasible and rapid technique to differentiate dark teas with similar morphological characteristics from different production areas by their volatile composition and relative content.3. Based on the fully HS-SPME/GC-MS and multivariate statistical methods, a novel model of identifying and evaluating the quality of Yunnan Pu-erh green tea was constructed for the first time in this work. Twelve Pu-erh green teas from12typical production sites in Yunnan province, and six regular green teas from Zhejiang, Sichuan, Anhui, Henan, Hubei, and Jiangsu province of China were used to construct the model. Data from18samples by GC-MS were processed with fingerprint technology and chemometric methods. The GC-MS fingerprint from12Pu-erh green teas whose correlation coefficients and congruence coefficients were over0.850and showed that Pu-erh green tea samples from the different production sites in Yunnan were consistent to some extent. A total of77volatile compounds were identified in18green teas, and their chemical compositions were slightly similar. CA and PCA demonstrated that12Pu-erh green teas could be clearly distinguished from other six regular green teas according to their chemical characteristics. Our results thus indicate that the chromatographic fingerprinting combine with multivariate statistical techniques is useful for the identity and consistency evaluation of Pu-erh green teas. Such an approach is believed to be equally applicable to other green teas.