Terpenes in citrus oil must be removed to stabilize the products and to dissolve it in aqueous solution. Supercritical fluid extraction has been investigated for the terpeneless citrus oil processing as a lower temperature process. In order to achieve higher yield and higher separation selectivity, a continuous countercurrent extraction with reflux was studied at a temperature of 333 K and a pressure of 8.8 MPa. Cold-pressed orange oil from Brazil and a model mixture of 80% limonene and 20% linalool, where limonene and linalool are principal constituent of terpenes and oxygenated compounds in orange oil, were used as feed and carbon dioxide was used as solvent. Operation at total reflux was carried out to calculate the minimum number of plates required to achieve a separation between limonene and linalool. Effects of the solvent-to-feed ratio, reflux ratio, and feed inlet position on the yield and selectivity were investigated for continuous operation. The selectivity increased with the increase in the solvent-to-feed ratio. Terpeneless citrus oil was obtained on the operation at the higher solvent-to-feed ratio and longer stripping section.

Extraction of dried sage and coriander seed was carried out using near critical carbon dioxide to obtain oleoresin, non-volatile oil and essential oil extracts. Extractions were carried out in both a 4 litre and 75 litre extraction plant, to determine the effects of the particle size, carbon dioxide flow rate, bulk density and extraction temperature and pressure on the yield and extraction time. The rate of extraction of oleoresin from sage depended only on the particle diameter, and was limited by intra-particle diffusion. The rate of extraction of non-volatile oil from coriander seed was limited both by its solubility in carbon dioxide, and intra-particle diffusion. The results were satisfactorily correlated with a mathematical model. Scale-up calculations were performed to enable the economics of the extraction process to be evaluated.

The application of the SRK equation of state for the prediction of the phase behaviour of mixtures of vegetable oils with near critical solvents is studied. The use of binary interaction parameters in the combinatorial rules for both the co-volume and the energy parameter is discussed. Two different sets of binary interaction parameters are needed in order to correlate the vapor-liquid and liquid-liquid equilibria. This indicates a serious limitation of van der Waals type of equations of state for modeling the phase equilibria of this type of systems.

Supercritical CO2 extraction of oleoresin from portuguese rosemary (Rosmarinus officinalis L.) was carried out with a flow apparatus at temperatures of 35 and 40 degrees C and pressures of 100, 125 and 200 bar. The highest fraction of volatile compounds (oil) in the oleoresin was obtained at 100 bar and 40 degrees C. An unsteady mathematical model was able to give good representation of the supercritical extraction curves and a mass transfer coefficient was determined using the successive quadratic programming method. Values of this coefficient ranged between 4.49 and 15.07 kg/m3s and the shift to a diffusion-controlled regime occurred when 44% of the total oil was extracted.