Supercritical extraction of fennel seeds (Foeniculum vulgare Mill.). [Doctoral dissertation]

Fennel (Foeniculum vulgare Mill.) seeds were extracted with supercritical CO2 (SC-CO2) as well, under varying extraction parameters in order to determine yield, composition and organoleptic properties. It was found that yield of essential oil as well as SC-CO2 extracts increases as fennel seeds particle size decrease. Also, content of oxygenated compounds, which are very important for the extract quality, raise as particle size diameter of the investigated herb decrease. Also, it was found that extraction of essential oil from weakly depends on the CO2 flow rate, which means that it is mostly controlled by inner-diffusion in the solid phase. It was found that with extraction pressure increase amount of extracted material increase as well. The highest extract yield was obtained by supercritical CO2 at 250 bar. However, in this extract the highest content of undesired cuticular waxes was detected while content of oxygenated compounds was very small. At 80 bar, an increase in temperature led to a rather significant decrease of the extraction degree due to decline of the solvent density, probably dominating over the increase of the solute vapour pressure. An opposite outcome was verified for 100 and 150 bar where the temperature alteration had a rather negligable influence on the essential oil yield. With pressure varied from 80 to 150 bar and temperature varied from 313 to 330 K, at particle diameter size d=0.93 mm and most favourable CO2 flow rate (3.225 x 10E-3 kg/min), it found that, for the selected herb material, the optimum conditions of SC-CO2 extraction (the high percentage of trans-anethole, with significant content of fenchone and reduced content of methylchavicol and co-extracted cuticular waxes) are: pressure, 100 bartemperature, 313 Kextraction time, 120 min. Additionaly, extraction kinetics was investigated at different pressure (80, 100, 150, 250 bar) and constant temperature (313 K), CO2 flow rate (3.225 x 10E-3 kg/min) and fennel seed particle size (d=0.93 mm), during 12 h of extraction and extraction was modeled through system: fennel seed - supercritical carbon dioxie.