High-pressure extraction of cork with CO2 and 1,4-dioxane

The extraction of cork from cork-oak (Quercus suber L.) by high-pressure dioxane and supercritical CO2 mixtures was studied at 170 bar and in the temperature range of 160 degrees C - 180 degrees C. Suberin is preferably extracted, but extraction percentages were lower than 46%. Lignin extraction percentages are lower than 11%. Extraction selectivity did not change significantly with extracting fluid composition. The results so far obtained support the idea of the existence of an extensive polymeric system across the cell wall and the concept of a close interaction of suberin and lignin, which hinders lignin depolymerization and solubilization in the high-pressure fluid. Fourier transform infrared spectra of cork, extraction residues and extracts are also presented.