Measurement of consolidation and permeability properties of extruded soy under mechanical pressing

A compression-permeability testing apparatus was developed to measure property functions of oilseeds relevant to mechanical pressing for oil recovery, namely time-varying coefficients of permeability, consolidation and volume change. The cell was designed to accommodate testing of different specimen depths, under various compression pressures and temperatures. Properties were measured for extruded soy for two specimen sizes (10, 20 g) compressed at three pressures (20, 40, 60 MPa) and three temperatures (22, 60, 90°C). Consolidation and permeability property functions were significantly affected by applied pressure, temperature, sample size and pressing time. Several of the key assumptions of classical consolidation theory (as developed for saturated soils) were violated for the extruded soy medium, namely, the assumption of incompressible solids phase and constant material parameters. In other words, the sample structure changed substantially during pressing. The designed testing apparatus may be used to measure time-varying material parameters for use with consolidation models that have been appropriately modified for compressible oilseeds.