| Based on the unique local sundried green tea variety as raw materials, Yunnan Pu-erh tea with special flavor was one kind of the tea made from post-fermentation. A novel method for simultaneous determination of residues of catechin(+)C, epigallocatechin(EGC), epicatechin gllate(ECG), epicatechin(EC), epigallocatechin gallate(EGCG) and caffeine(CAF) in Pu-erh tea by high performance liquid chromatography was investigated firstly. Then according to the previous studies, this study aimed to explore the optimum technical parameter and monitored the sensory indicators and chemical indicators for fast fermentation process which was kept constant temperature and humidity and produced by adding advantaged microbes in Pu-erh tea. After that, we analyzed the correlation between chemical compontents and sensory quality in Pu-erh tea. The main results of this study were as follows:1. The optimal condition for the chromatography was found through the research of the influential factors such as the property, the proportionment, the acidity, the flow rate, the column temperature and the determining wavelength on the separte degree of catechins and caffeine. Under above condition, catechins and caffeine were quickly separated on a SPHERI-5RP-185UM C18 (250mmx4.6mm,5μm) using actonitrile-0.05% phosphoric acid at the flow rate of 1.5ml/min, the column temperature of 30℃and detected at the wavelength of 207 nm.2. Analysis of gradient elution condition and its influential factors was determinated. The results indicated that the direct ratio between elution time and sepatate degree, and the reverse connection between gradient and separate degree, and the best separation were attained by changing the concentration of organic phase and the curve shape. Catechins and caffeine were quickly separated on actonitrile density form 10% up 55% and phosphoric acid density form 90% down 45% in 30 min.3. In Pu-erh tea sample, sample solutions were stabilied within 12 hours, precision of six components were less than 1.25% and the recoveries (RSD) varied form92.98%-103.67%, and the relative standard deviations(RSD) was<2.95%. The linearity was obtained over the range of 0.014-0.144mg/ml and with all the correlation coefficients were higher than 0.9994, which indicated that the method was simple, rapid and accurate.4. The experiment was dedermined the best technologic parameters during the fast fermentation process in Pu-erh tea as follows:microbes dosage is 20ml, moisture at 30% and temperature at 55 degrees. Compared to the traditional file-fermentation processing, the entire fast-fermentation only taked 30 days, with the quality of the experiment sample which the sensory test result was 90 points was similar to the quality of sample which the sensory test result was 92 points in traditional processing.5. Sensory quality monitoring results indicated that sundried green tea through fermentation into Pu-erh tea, and its sensory quality changes largely. Chenmical quality monitoring results showed that the containing material had changed dramatically during the processing. To the end of fermentation, tea polyphenol, EGCG, ECG, (+) C, EC, EGC and caffeine contents have declined, while the water extract content increased significantly.6. The correlation equation for the content of chemical compontents and the quality of Pu-erh tea is as follows:Y=38.793+9.216X1-15.415X2-4.867X3-7.389X4, the correlation coefficient is 0.893,-0.925,-0.945å'Œ-0.947, respectively. This equation showed that in certain range, the water extracted content of is positive for the quality and the content of tea polyphenol, EGCG, ECG is negative for the quality of Pu-erh tea. |
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