Mass Transfer and Kinetic Modelling of Supercritical Co2 Extraction of Fresh Tea Leaves (Camellia Sinensis L.).

Supercritical carbon dioxide extraction was employed to extract solids from fresh tea leaves (Camellia
sinensis L.) at various pressures(15 to 35 MPa) and temperatures (313 to 333K) with addition of ethanol as a polarity
modifier. The diffusion model and Langmuir model fit well to experimental data and the correlation coefficients were
greater than 0.94. Caffeine solubility was determined in supercritical CO2 and the Gordillo model was employed to
correlate the experimental solubility values. The Gordillo model fit well to the experimental values with a correlation
coefficient 0.91 and 8.91% average absolute relative deviation. Total phenol content of spent materials varied from 57
to 85.2 mg of gallic acid equivalent per g spent material, total flavonoid content varied from 50.4 to 58.2 mg of rutin
equivalent per g spent material and the IC50 value (antioxidant content) varied from 27.20 to 38.11 μg of extract per
mL. There was significant reduction in polyphenol, flavonoid and antioxidant content in the extract when supercritical
CO2 extraction was carried out at a higher pressure of 35 MPa.