| Composition and content of chemical substances of fresh tea leaves is to form the basis of the quality of tea. The total content of carbohydrate, protein and total tea polyphenols, take the percentage of the weight of dry tea leaves more than70%. And the content of tea polyphenol, caffeine and theanine, respectively accounted for15-35%,2-5%and1-3%of the weight of dry tea leaves, which is not only the main chemical composition of tea, but also as an important factor to decide tea drinking quality.This study take the fresh tea leaves of10varieties of tea plants in spring and autumn seasons and the fresh tea leaves of the same variety under different protected facilities as the research objects, using the ultrasonic oscillation extraction joint high performance liquid chromatography to quantitative analyze the content of the main chemical substances for drinking in fresh leaves of tea plants including tea polyphenols, caffeine and theanine. Comparative analysis of the difference of the main chemical substances content for drinking in fresh leaves of10different varieties of tea plants in spring and autumn seasons and the influence of main chemical substances of fresh tea leaves under frost prevention fan, sun-shade net and greenhouse facilities cultivation, in order to provide a reference for the tea variety selection and for facility cultivation promotion and optimization. The main results of the study are as follows:1) Significant difference of tea polyphenols content in varieties of fresh tea leaves between spring and autumn season is very big, and the content and composition of six kind of catechin is different, the content of which basically following the rule:EGCG>ECG>EGC>EC>C>GC. AnJiBaiCha has the lowest content of tea polyphenol and caffeine but the highest content of theanine; the same variety, but different seasons, the content of tea polyphenol, caffeine in fresh leaves in spring is few but in autumn is much; and the theanine content in spring is generally much but that content in autumn is few. The ratio of tea polyphenols and theanine in spring is generally lower than8, and mostly in autumn is higher than8; The bitterness indication index of catechins in autumn is higher than that in spring. So the drinking quality of green tea in autumn is no match for that in spring.2) The content of tea polyphenol of WuNiuZao fresh leaves under frost prevention fan compared with that in open-air tea garden(CK) decreased by8.38%. The content of tea polyphenol of LongJingChangYe under sun-shade net compared to CK increased by8.49%. The content of tea polyphenol of LongJingChangYe fresh leaves that picking up in advance in greenhouse compared to CK decreased by14.13%, while the tea polyphenol content of LongJingChangYe fresh leaves that in greenhouse picking up in the same time of which picking up in open-air tea garden increased by13.90%. The content of theophylline of fresh leaves under the three facilities all decreased, and the content of CAF of fresh tea leaves under the frost prevention fan and fresh leaves in greenhouse (picking up in advance) compared to that in open-air garden respectively decreased by4.00%and3.46%, the content of CAF of fresh leaves under sun-shade net and in greenhouse (the same time of fresh leaves picking up in open-air tea garden) respectively increased by13.20%and9.46%; the content of theanine of fresh tea leaves under frost prevention fan, sun-shade net and fresh tea leaves in greenhouse (picking up in advance) compared to open-air tea garden respectively increased by37.37%,13.21%and31.55%, the ratio of tea polyphenols and theanine under this three conditions all decreased, so help the quality of fresh taste of tea plants can be significantly improved. Therefore, those facilities conditions in the early spring can prevent frost and at the same time those also have a significant impact on the dringking quality of fresh tea leaves.3) Regard LongJingChangYe growing in open-air tea garden as CK, tea polyphenols were decreased by20.58%; The content of tea polyphenol in greenhouse facilities conditions increased by9.67%. Under two kinds of shading facilities the content of theophylline in fresh tea leaves were respectively increased by65.96%and115.77%, the content of caffeine is reduced by1.67%and6.37%, respectively. The theanine content of LongJingChangYe fresh tea leaves under the condition of75%sun-shade net increased by7.02%; While the theanine content under the condition of greenhouse was reduced by3.19%. The content of tea polyphenols of fresh leaves under the condition of frost prevention fan in autumn is basically on the downtrend; the content of theophylline of fresh tea leaves in the center of the role position of frost prevention fan all increased, the content of caffeine at various location under the frost prevention fan decreased by1.74%～11.34%; the theanine content is relatively increased by6.48%～18.41%, Sun-shade net covering in summer will help improve the content of theanine in fresh leaf tea leaves in autumn, significantly, reduce the content of polyphenols and reduce the ratio of tea polyphenols and theanine, improve the tea drinking quality, but the greenhouse is the opposite; the use of frost prevention fan in spring also has the following beneficial effects on the tea plants in autumn. |
