Analysis of the axial pressing of bulk Jatropha curcas L. seeds using reciprocal slope transformation

A reciprocal slope transformation (RST) with the least squares method (LSM) was used to develop mathematical equations to describe dependency between compressive force and deformation characteristic curves of Jatropha bulk seeds of varying initial pressing height from 30 mm, 40 mm, 50 mm, 60 mm, 70 mm and 80 mm in linear compression. The experimental data derived from a compression test was done using compression device (ZDM, model 50, Germany) and pressing vessel diameter, 60 mm at compression speed of 1 mm s−1 and compressive force between 0 kN and 100 kN. Statistical analysis of both experimental and fitted data coefficients of third order polynomial function was significant (p > 0.05) with high coefficient of determination (R2). The RST method provides the fundamental step for the development of generalised model in future research where varying effect of compression factors such as moisture content, friction, compression speed and pressing temperature would be considered.