| Tea, one of the most consumed beverages, plays an important role in our daily life. However, tea quality is mainly evaluated by Sensory method which is casual, subjective and easy to be influenced by the external environment. A method was established to evaluate tea quality according to the constituents.The main methods and conclusions were as follows:1.58 big-leaf tea samples from three seasons were collected from Nanjian on Dali county in Yunnan province, and the contents of tea catechines (TC), caffeine, tea polysaccharides (TPS) and volatile compounds were determined. Caffeine and tea catechines (TC) were analyzed by HPLC, tea polysaccharides (TPS) was determined by anthrone-sulfuric acid method, and volatile compounds was analyzed by GC-MS. All of their data were analyzed by principal component analysis and cluster analysis. The results showed that wild type tea had larger dispersion for its biodiversity. Cultivated type tea was analyzed separately with excluding wild type tea. There was some difference between tea samples collected from different seasons. Especially, spring tea was superior to the tea samples in other seasons indeed. Finally, the harvested place near Lancang River where the moisture content in air was higher, which was of great influence for tea’s growth. In conclusion, the method we established could be used to distinguish spring tea sample from summer and autumn successfully. The ratio (EGCG+ECG) ×100/EGC and catechin index (CI) [(EC+ ECG)/(EGC+EGCG)] were also calculated, which were used in many cases to distinguish tea samples collected from different seasons. However, it failed in this case.2. To establish an effective method for quantitative analysis of multi-components with a single-marker for the content determination of catechin in tea. ECG was used as the internal standard. And the relative correlation factors (RCF) of other three main ingredients to ECG were calculated. At the same time, to prove the feasibility of QAMS, contents of these three ingredients were determined by the external standard method. The result above showed these two methods did not show significant difference in assay results of contents of these three ingredients.3. The ingredients in four dark tea samples were identified tentatively by LC-MS. There was no obvious difference between the HPLC spectrogram, while the LC-MS spectrogram was just the reverse. The structure of Puerins which is unique in pu’er tea, was formed by 8 position of catechins A ring addition nitrogen-containing five-membered ring; Teasperol could be only detected from pu’er ripe tea, Ya’an dark tea, and the content of which in the former was higher than the latter. Quinic acid could be detected from Guangxi dark tea and Anhua dark tea. Furthermore, quercetin, kaempferol and other flavonoid glycosides were widely distributed in dark tea. On the basis of our research advance in the four post-fermentation tea, the difference between them may be correlated to the advantage zymogeneous bacteria, raw materials or localities. However, it is necessary to make a further study.4. We established a method to evaluate tea quality from six aspects. The color of tea infusion, astringent, fragrant, sweet, bitter and fresh were represented the content of various constituents of tea. And a radar program was made to reflect the quality of tea intuitively. |
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