SUPERCRITICAL CARBON-DIOXIDE EXTRACTION OF PEPPERMINT AND SPEARMINT

Peppermint and spearmint-oils were extracted from cut green plants and field-dried hay with liquid and supercritical carbon dioxide at 297 to 316 K and 6 to 18 MPa. Solvent treatment was varied from 6 to 30 g CO2/g dry plant material. Extraction time was varied from 4 to 9 hours. Extraction vessel charge sizes were 4.4 and 33 L. Downflow of carbon dioxide through the bed of mint plants was more effective than upflow. Essential oil compositions and attainable yields were nearly the same as those by steam distillation when single pass mode of CO2 with depressurization to atmospheric pressure was used for oil recovery. The recovery of the terpene constituents was reduced when using depressurization to 3-6 MPa for oil recovery and recycle Of CO2. The flavor and fragrance of the carbon dioxide mint extracts were closest in quality to actual mint plant leaves, compared to mint oils produced by conventional steam distillation.