title: Solubility of caffeine from green tea in supercritical CO2: a theoretical and empirical approach.
abstract: Decaffeination of fresh green tea was carried out with supercritical CO2 in the presence of ethanol as co-solvent. The solubility of caffeine in supercritical CO2 varied from 44.19 × 10(-6) to 149.55 × 10(-6) (mole fraction) over a pressure and temperature range of 15 to 35 MPa and 313 to 333 K, respectively. The maximum solubility of caffeine was obtained at 25 MPa and 323 K. Experimental solubility data were correlated with the theoretical equation of state models Peng-Robinson (PR), Soave Redlich-Kwong (SRK), and Redlich-Kwong (RK). The RK model had regressed experimental data with 15.52 % average absolute relative deviation (AARD). In contrast, Gordillo empirical model regressed the best to experimental data with only 0.96 % AARD. Under supercritical conditions, solubility of caffeine in tea matrix was lower than the solubility of pure caffeine. Further, solubility of caffeine in supercritical CO2 was compared with solubility of pure caffeine in conventional solvents and a maximum solubility 90 × 10(-3) mol fraction was obtained with chloroform.
authors.affiliation: Department of Food Engineering, CSIR (Council of Scientific and Industrial Research, India) - Central Food Technological Research Institute, Mysore, 570 020 India ; Academy of Scientific and Innovative Research, CSIR-CFTRI, Mysore, India.
authors.forename: Pravin Vasantrao
authors.initials: PV
authors.lastname: Gadkari
authors.affiliation: Department of Food Engineering, CSIR (Council of Scientific and Industrial Research, India) - Central Food Technological Research Institute, Mysore, 570 020 India ; Academy of Scientific and Innovative Research, CSIR-CFTRI, Mysore, India.
authors.forename: Manohar
authors.initials: M
authors.lastname: Balaraman
keywords: Caffeine; Equation of state; Green tea; Redlich-Kwong; Solubility; Supercritical CO2