Extraction Of Tea Polyphenol And Caffeine Under Supercritical Dioxide Condition With Co-solvents From Green Tea Leaves

Tea polyphenol and caffeine are two of the most important active ingredients in green tea leaves. This paper is to search more effective and convenient ways to separate tea polyphenol and caffeine from leftovers of tea industry.The solubility of EGCG (main components of tea polyphenol) is measured at co-solvent containing ethanol 5%,10%,15%(V/V), temperature 313K,323K,333K, pressure 15-35MP condition using supercritical phase equilibrium instruments. Furthermore, we also determined the solubility of caffeine. The experiments results show that EGCG's solubility is higher at ethanol co-solvents when we add the same percent of ethanol or acetone co-solvents, it may be account for hydroxide forming hydrogen bond. With the increase of ethanol co-solvents content and pressure, the solubility increase accordingly. The maximum solubility of EGCG under supercritical dioxide is 7.34×10-4 mol/mol at pressure 35MP, Temperature 313K, co-solvents 10%. The maximum solubility of caffeine is 35×10-4 mol/mol. At the end, EGCG's solubility shows the good correlation to experiment results using PR model results.According to the above solubility measured at supercritical phase equilibrium instruments, we studied the effect of pressure, temperature, co-solvents, pre-treatment conditions on experiment results. Firstly we obtain caffeine of impurity and yield 88%,98.7% separately, and then we get tea polyphenol of impurity and yield 58%,75% separately at continuous extraction.