Polyphenols from fresh frozen tea leaves (Camellia assamica L.,) by supercritical carbon dioxide extraction with ethanol entrainer - application of response surface methodology.

Fresh frozen tea leaves (Camellia assamica L.)
were extracted with SC-CO2 to obtain polyphenols rich in
EGCG and compared with conventional solvent extraction.
Extraction parameters such as temperature, pressure and
solvent to material ratio were critical factors in extraction
and optimized by response surface methodology (RSM). The
maximum yield of extractable solids using SC-CO2 with
ethanol entrainer was carried out at pressures 150 to
350 bar, temperatures from 40 °C to 60 °C and solvent to
material ratio 100 to 200. The theoretical yield was 3.91 %
(w/w), while experimental yield was 4.20±0.27 % (w/w) at
temperature of 50 °C, pressure 250 bar and solvent to material
ratio of 200. The chemical compositions of extracted
solids were investigated by HPLC which showed 722.68–
848.09±1.12 mg of EGCG/g of extractable solids were
separated in SC-CO2. Also, 54.62±1.19 mg of EGCG/g of
extractable solids was separated using conventional extraction
which is quantitatively lesser than SC-CO2 extraction
yield. Thus, SC-CO2 extraction was proved to be effective
technique in obtaining extracts rich in EGCG (>95 %).