Linear pressing analysis of Jatropha curcas L. seeds using different pressing vessel diameters and seed pressing heights

The mechanical properties of Jatropha curcas L. seeds of initial moisture content 10% (w.b.) were examined in a compression loading test using different pressing vessel diameters 40, 60, 80 & 100 mm and seed pressing heights 20, 30, 40, 50, 60, 70 & 80 mm. The maximum pressing force of 100 kN with a compression speed of 1 mm s−1 was used to record the force–deformation characteristics. Based on the dependency between the maximum pressing force and deformation of the varying seed pressing heights; parameters including the maximum deformation (mm), deformation energy (J), seed hardness (N mm−1) and amount of oil in seed (g) were determined. The results showed that for all pressing vessel diameters, increasing the seed pressing heights directly increased the deformation, deformation energy and the amount of oil. However, the relationship between deformation and pressing vessel diameter, in relation to the seed pressing heights, showed a negative correlation whilst that of deformation energy and pressing vessel diameter showed a positive correlation. The seed hardness for all pressing vessel diameters decreased with respect to seed pressing heights where polynomial function best described the relationship. A linear regression equation was determined for the seed deformation, seed deformation energy and amount of oil as a function of seed pressing heights and pressing vessel diameter.