Effect of ethanol content on carbon dioxide extraction of polyphenols from tea

This study presents a novel packed-column extractor coupled with an absorption system to improve the quality of oleoresin oils for Oolong and green teas, extracted by using carbon dioxide, The effect of various co-solvents on the extract is also examined. In addition, gravimetrical measurement and HPLC chromatographic analysis individually determine the amount of oleoresin oil and the concentration of four major catechins. According to those results, the mean contents in the extract are 7.0- and 10.0-fold higher in an addition of 95% ethanol than in no addition for green tea and Oolong tea, respectively. The ratio of four major catechins to caffeine is the highest in Soxhlet ethanol extraction for both green and Oolong teas. (C) 2001 Academic Press.