Gas assisted mechanical expression of oilseeds: Influence of process parameters on oil yield

Gas assisted mechanical expression (GAME) utilizes the solubility of supercritical CO2 in vegetable oils to enhance the oil yields of mechanical expression of oil seeds. The general applicability of GAME was demonstrated with experiments with sesame, linseed, rapeseed, palm kernel and jatropha (hulled and dehulled) at 40 °C and varying mechanical pressures (10–70 MPa). Furthermore, the influence of moisture content, temperature and CO2-pressure on oil yield and rate of seedbed compaction was investigated. Yields obtained with GAME were up to 30 wt.% higher than conventional expression at the same effective mechanical pressure and temperature. GAME yields for hulled and dehulled seeds were very similar, despite the lower yields for hulled seeds in conventional expression. Up to 10 MPa CO2 yield increased significantly with CO2-pressure. The displacement of oil by dissolved CO2 was identified as the major cause of increased oil yields for both hulled and dehulled seeds. The entrainment of oil during CO2 depressurization is another major cause of increasing oil yield for hulled seeds.