Optimisation of olive paste expression: maximizing yield by central composite design approach

This work shows results from an optimisation test of olive paste expression. A factorial design was first used to evaluate the effect of the simultaneous variation of the following parameters on the extraction yield: pressure, compaction rate, cake thickness and solids content in the olive paste. It was found that the most important variable for the yield is the rigid solids content, followed by pressure, cake thickness and compaction rate. A central composite design procedure was then applied to identify optimum conditions. The highest extraction yield (983·6 g kg- 1) was obtained at low cake thickness (9 mm), high pressure (7598 kPa) and high solids content (450 g kg-1). This extraction yield is much higher than the yield obtained in commercial operations (<850 g kg -1). Furthermore, this result was obtained within a very short time (the time of the extraction phase at constant outflow rate, ie about 1 min), while industrial operations usually last 1 h or longer.