Effect of CO2 pre-treatment on scCO2 extraction of natural material

Pre-treatment of natural materials prior to their extraction strongly influences the efficiency of the process. Therefore, proper selection of pre-treatment method enables intensification of extraction process. Within this study “rapid gas decompression” (RGD) was investigated as a pretreatment method using carbon dioxide as working fluid. Oilseeds (rapeseed and sunflower seed), St. Johns Wort and Hop were studied as valuable raw materials for industrial application of supercritical fluid extraction. The sorption behaviour of carbon dioxide within the natural materials was examined gravimetrically under high pressure conditions between 5 and 26 MPa and at temperatures between 40 and 60 °C. It was observed that considerable amounts of carbon dioxide sorb within natural materials and a combination of dissolution within the solute phase and adsorption on the plant matrix occurs. RGD was used as a pre-treatment method prior to the extraction or as an intermediate treatment during the extraction process. The results showed that effect of RGD on extraction was the most pronounced for St. Johns Wort but also the extraction kinetics of the other materials were affected. Probable mechanisms occurring during RGD are discussed.