Energy demands for pressing Jatropha curcas L. seeds

Experiments were carried out to determine required energy for pressing Jatropha curcas L. seeds (IPB2 variety from Indonesia), at three stages of fruits maturity, i.e. green (unripe), yellow (ripe) and brown (over-ripe), using two pressing techniques (cold 20 °C and hot 60 °C). Relationships between the pressing force and absolute seed deformation, the size of stress and relative seed deformation, and the seed modulus of elasticity in compression were calculated. Specific regions of pressing and adequate pressing force size interval were specified. The limit points for pressing any maturity stage of J. curcas L. seeds were defined: the lower limit of the relative deformation (lower oiliness point) ɛL = ɛmezI = 0.4, and the upper limit of the relative deformation (upper oiliness point) ɛU = ɛmezII   = 0.8. The following equations were defined as being generally applicable for the pressing of seed mixtures. The relationship between pressing force value and absolute seed deformation was F(ΔL)=155⋅tan(0.157⋅ΔL)F(ΔL)=155⋅tan(0.157⋅ΔL), where F (N) is the pressing force and ΔL   (mm) is the deformation. The relationship between the compressive stress and relative deformation was σ(ɛ)=0.863⋅tan(1.571⋅ɛ)σ(ɛ)=0.863⋅tan(1.571⋅ɛ), where σ (MPa) is the compressive stress and ɛ   (−) is relative deformation. The relationship between the modulus of elasticity in compression and relative deformation was E(ɛ)=1.3558⋅[1+(tan(1.571⋅ɛ))2]E(ɛ)=1.3558⋅[1+(tan(1.571⋅ɛ))2], where E   (MPa) is the modulus of elasticity in compression. The relationship between deformation volume energy and relative deformation was W(ɛ)=[0.275⋅ln[1+(tan(1.571⋅ɛ))2]]ɛ1ɛ2, where W (J mm−3) is the deformation volume energy.