Extraction, Purification And Characterization Of Tea Polyphenols Polysaccharides From Oolong Tea

The thesis mainly studied the general extraction and purification of tea polyphenols and tea polysaccharides in low grade Oolong Tea.Via the discussion and analysis, the conditions of extraction of tea polyphenols and the condition of ultrafiltration of tea-water system have been determined , the purification with resins about tea polyphenols have been explored, besides, the product prepared by tea polyphenols-catechins has been analyzed by HPLC in this paper.With regard to the extraction of tea polysaccharides ,I mainly studied the extraction parameters of the method of the tea polysaccharides extracted by water, and conducted initial purification using the method of Sevag remove the protein,meanwhile,studied the activities and the compositions of the monosaccharides of tea polysaccharides. Finally, the process conditions between the comprehesive extraction of tea polyphenols and the comprehesive extraction of tea polysaccharides have been compared and studied.In the process of extraction of tea polyphenols, the influences caused by some factors on the extraction of tea polyphenols was studied, and the optimum conditions of extraction was determined by the orthogonal experiment. The optimum conditions are as follows:solvent is 60% ethanol-water solution ,the temperature of extraction is 70℃, the time of extraction is 25minites, the ratio of tea and solvent is1:20, the times of extraction are 2,the maximum yield of tea polyphenols is 25.10% under this condition.Using the method of ultrafiltration to refine the system of extracted liquid of tea, it proved that ultrafiltration is not only get rid of the impurities but also prevent resin from being polluted. Through the static and dynamic experiments of adsorption-desorption, the process parameters of PA and XDA resin are determined.The total yields of TP and the by-products caffeine are respectively 13.68% and1.59% when 85% ethanol is adopted as elution solvent. The contents of four kinds of catechins have been detected by the method of HPLC, content of EGC is 11.79%, content of EC is1.16% ,content of ECG is 15.89% and content of EGCG is 51.97%,and the total contents of the four kinds of catechins is up to 80.81%.The effects of the ratio of tea to water, the extraction temperature, the extraction time, the number of extraction times on the yield of tea polysaccharides were studied and the optimum parameters for the extraction of tea polysaccharides were obtained by orthogonal test in the process of the extraction of tea polysaccharides. The optimum parameters were as follows:the ratio of tea to water is 1:25, the extraction temperature is 55℃, the extraction time is 150min and the number of extraction times is 3. Under the condition above, the maximum yield of tea polysaccharides reached 1.75% and the content of polysaccharide is 23.12%. The times of de-protein operates was determined as three. By gas chromatography analyses, their compositions ofmonosaccharides were gained:Rha,Ara,Glu and Gal.,their molecular ratio is 4.21: 24.66:43.71:27.42.The optimum process of the comprehensive extraction of oolong tea polyphenols and tea polysaccharides were obtained in this experiment, and the yields of oolong tea polyphenols, oolong tea polysaccharides and caffeine respectively were 13.68%, 2.084%,1.59% under the condition above.