Experimental and modeling study of supercritical CO2 extraction of Quercus cerris cork: Influence of ethanol and particle size on extraction kinetics and selectivity to friedelin

Turkish oak (Quercus cerris) cork is an interesting source of friedelin, a bioactive triterpenoid. In this work, the supercritical fluid extraction of Q. cerris cork was carried out in order to measure cumulative curves for both total and friedelin extraction yields (ηtotal and ηfriedelin). The influence of particle size and ethanol (CO2 modifier) content were assessed in the ranges of coarse particles to >80 mesh size, and 0-5 wt.%. The 14 experimental curves were modeled using the broken plus intact cells model, being attained global errors of only 4.43% (ηtotal) and 4.25% (ηfriedelin). Moreover, an analysis of the extraction periods allowed to get insights on the impact of the operating conditions on the duration and yields attained under the constant extraction rate (CER) period. Finally, an assessment of the selectivity to friedelin was also accomplished, being concluded that intermediate particle sizes (40-60 to 60-80 mesh) are preferable for uptaking friedelin, and also that the ethanol addition favors the competitive removal of this compound but only up to a limiting extent. In the whole, this article documents the influence of particle size and ethanol content can affect the production of friedelin-enriched extracts by supercritical fluid extraction, enhancing ηtotal up to 230% and ηfriedelinupto 353%.