Supercritical Carbon Dioxide Extraction of Eugenol from Clove BudsProcess Optimization and Packed Bed Characterization

Isolation of eugenol from dried clove buds (Syzygium aromaticum Linn) of Indian origin was carried out using supercritical carbon dioxide (SC-CO2) extraction. Optimization of its process parameters such as temperature, pressure and time of extraction has been conducted using response surface methodology. The optimized conditions that provided the optimum yield of eugenol were a sample size of 20 g of clove powder of particle diameter 0.5 mm at a temperature of 60°C and pressure of 250 bar for 90 min extracting time at a flow rate of 2 l min−1 of CO2. Statistical analyses conducted on the extraction parameters concluded that extraction temperature have significant effect on the yield of eugenol, whereas extraction pressure and time do not. The results obtained are in accordance to the basic principle of supercritical fluid phase equilibrium behavior. Solubility of eugenol in SC-CO2 under different temperature and pressure regimes have been determined experimentally and values were used to construct a correlated Chrastil equation in linear form to allow the prediction of solubility of eugenol in SC-CO2 under different extraction conditions. Using dimensionless numbers, an empirical correlation was also deduced for characterization of the extraction process of eugenol in SC-CO2 considering overall fixed bed behavior for clove matrix and mass transfer coefficients in supercritical phases.