Studies On Comprehensive Extraction Technology Of Active Principles Of Tea

Using mid-grade and low grade green tea as raw material, Comprehensive technology of extracting Tea-polyphenols, Tea-polysaccharide and caffeine was studied in this paper. The effect of microwave treatment on Tea-polyphenols ' leaching character was probed and the technology of extracting Tea-polyphenols, Tea-polysaccharide, caffeine from the same tea material was constructed.The result demonstrated that microwave treatment could improve leaching active principles of green tea. Using purified water as the solvent, being leached 2 times by microwave (material-water ratio 1:20, Time:3min), then Green tea of average size 0.246mm was leached by purified water (50 ) 1 time in 10 minutes. The result showed that the leaching rate of tea polyphenols was 90.73%, which was higher than that of being leached by the mixture of ethyl alcohol and water. The analysis of HPLC demonstrated that among the tea-polyphenols production extracted by microwave treatment, there was a little alteration in catechin composition and it had a slight decrease to the contents of EGCG and ECG. But the decreasing amount was far lower than that of boiling water extraction. At present, the researches about extracting active principles of tea by microwave are few.Using A13+ to sediment tea- polyphenols, it was also revealed that the best range of pH was from 5.3 to 5.7. Using acid solution with pH1.5 to dissolve TP-A13+ (ratio between experimental solution and acid solution was 1:2), the mixture of acid solution and TP-A13+ was soaked in the water (50 ) in 15 min. The result showed that it was the best dissolved condition and the dissolved rate was 79.09%.Combined extractive method with sublimational method to prepare caffeine, the result showed that the production of caffeine was higher than direct sublimational preparation. It was also revealed that the experimental solution among which the concentration of NaCl was 0.2% was extracted 2times by acetic ether, the extraction rate was 95.14%.Using purified water as the solvent, leached by microwave treatment and water, separated by solvent extraction and sedimental extraction, tea power could prepare Tea-polyphenols about 11.8%, Tea-polysaccharide about 1.5% and caffeine about 1.2%, Which was remarkably superior to single solvent extraction and sedimental extraction.The analysis of UV-VIS and IR confirmed that the separation of this technology had no influence on the chemical structure of Tea-polyphenols, Tea-polysaccharide and caffeine.The analysis of HPLC demonstrated that the Tea-polyphenols production mainly contained three kinds of catechin: EGC, EGCG and ECG. The total production of catechin constituted 78.4% of Tea-polyphenols, among which the content of EGCG was the highest and constituted about 45.8% of the total production of catechin.