The possibility of extracting capsaicin with supercritical carbon dioxide from a hydroalcholic mixture containing the alkaloid was investigated. High-pressure phase equilibrium on the quaternary system CO2 + ethanol + water + capsaicin was measured in order to obtain the separation factor of the natural product from hydro-alcoholic model mixtures. Experiments on phase equilibrium behavior were performed at several pressures (12, 15 and 18 MPa) and temperatures of 40 and 50 degreesC. The separation factors for three mixtures of different composition - 0.40 water + 0.60 ethanol mass fraction and 0.9 water + 0.10 ethanol mass fraction, containing 0.02% of capsaicin and 0.40 water mass fraction containing 0.04% of capsaicin-are compared. The effect of the water content in the selectivity of the extraction process is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.