Selective caffeine removal from green tea using supercritical carbon dioxide extraction Original Research Article

Caffeine and EGCG (epigallocatechin gallate) were extracted from green tea using supercritical carbon dioxide (SCCO2) with water as a cosolvent. Experimental conditions were carefully chosen to selectively extract a large amount of caffeine from the green tea while to remain a large amount of EGCG in the green tea. Various experimental conditions were explored including temperatures ranging 40–80 °C, pressure ranging 200–400 bar, and water contents ranging 4–7 wt%. At 40 °C, 400 bar and the water content of 7 wt%, the caffeine extraction yield was 54% while the EGCG extraction yield was 21%, resulting in caffeine/EGCG extraction selectivity of 2.57. The larger caffeine extraction yield agreed well with estimation of solubility parameter differences between SCCO2/water and caffeine/EGCG. The extraction results using SCCO2/water were compared with conventional liquid solvent extraction using water or ethanol. The selectivity of caffeine/EGCG extraction with water was 0.88 and the selectivity of caffeine/EGCG extraction was 0.24 with ethanol. Thus SCCO2 extraction with water as a cosolvent is suitable for the selective extraction of caffeine from the green tea.