EXTRACTION OF PEPPERMINT OIL BY SUPERCRITICAL CARBON-DIOXIDE

The extraction of essential oil from peppermint leaves with supercritical carbon dioxide was studied in a semibatch-flow extraction apparatus. The extraction rates of the major components, l-menthol and menthone, were measured at various conditions: 313-353 K, 8.83-19.6 MPa. The exit concentration of l-menthol extracted from peppermint leaves was much smaller than the solubility of l-menthol. The extraction curves at various flow rates coincide in the plot of yield versus quantity of CO2 consumed. A mathematical model based on the local adsorption equilibrium of essential oil on lipid in leaves and mass transfer well described the extraction results. The adsorption equilibrium constant determined by fitting the theoretical extraction curve to the experimental data increased with temperature and decreased with pressure.