A sphere surrounded by a shell is deformed on both sides and assumes the shape of a barrel when compressed between two parallel plates. Further cotyledons deformation causes shell filling, leads to increase of the shell stress till its disruption. The approximated stress of the shell surrounded the compressed rapeseed can be calculated from the Lamé equation. A rapid increase of surface area for deformation of seed over value l = 0.3 correctly reflects damage of wet rapeseeds in the range of large deformation. The above method enabled the interpretation of the forcedeformation curve for large deformation of non-elastic wet rapeseeds, where mechanical strength is mainly connected with the resistance of seed shell to tension. The modulus of elasticity determined in compression tests of whole seeds achieved value in the range 125-131 MPa (for the moisture level of 17% ). and 174-180 MPa (for the moisture level of 14%).