원문정보
초록
영어
Green tea (Camellia sinensis) has recently receiving increasing attention due to its health-benefiting effects primarily caused by catechins including epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin g1allate (ECG), and epicatechin (EC). However, caffeine contained in the green tea is found to cause adverse physiological effects such as sleep deprivation, miscarriage, and nervousness. To remove caffeine from green tea leaves, we have employed supercritical carbon dioxide (SC-CO2), which is known to be an ideal solvent, coupled with a cosolvent such as ethanol or water. By varying the extraction conditions including temperature, pressure, cosolvent, particle size, and CO2 flow rate, not only changes in the amount of caffeine, but also the quantities of the principal bioactive components of green tea, including catechins, such as EGCG, EGC, ECG, and EC, were investigated. The extraction yield of caffeine increased with an increase in temperature at a constant pressure, and also at different pressures at a fixed temperature. As the content of the ethanol or water used as a cosolvent increases, the extraction yield of caffeine significantly increased. Comparing with the results of ethanol and water, caffeine was much more effectively removed when ethanol was used, but the loss of EGCG by extraction was similar to water and ethanol. When the CO2 mass flow rate increased, the total extraction yield of caffeine also increased, but the extraction efficiency of CO2 (amount of caffeine extracted per amount of CO2 used) decreased. The reduction of green tea leaf particle size by grinding also resulted in the enhanced extraction of caffeine. The caffeine content in the decaffeinated green tea was reduced to 2.6% of the initial content after extraction with SC-CO2 modified with 4.6 g of 95% (v/v) ethanol as a cosolvent per 100 g of CO2 at 300 bar, 70°C, mean particle size of 236.5 µm for the ground green tea, and CO2 flow rate of 11.5 g/min for 120 min. However, after the extraction, a substantial loss of EGCG, as much as 40% of original content, proved unavoidable.