Hydraulic pressing of oilseeds: Experimental determination and modeling of yield and pressing rates

The influence of pressure, temperature and moisture content on the oil yield and rate of conventional hydraulic expression of sesame and linseed is discussed as well as the influence of pressure and temperature for rapeseed, palm kernel, jatropha and dehulled jatropha. Yield increased with increase in pressure and with increase in temperature. For both sesame and linseed maximum oil yield was obtained at a moisture content of about 4 wt%. Maximum yields obtained were 45–55 wt% (oil/oil) for hulled seeds (linseed, rapeseed, palm kernel and jatropha) and 70–75 wt% (oil/oil) for dehulled seeds (sesame and dehulled jatropha). Rate of expression increased with an increase in temperature and a decrease in moisture content. Furthermore, the rate of pressing was described by the Shirato model. The increased creep, and thus decreased rate of pressing, observed with increased moisture content was satisfactorily described by the Shirato model.