The aim of this work was to develop a mathematical model describing the evolution of rupture force, absorbed energy and deformation at rupture point. The models exploit the theory of the mechanical behavior of sunflower seeds and its kernel with moisture content, variety, size and loading orientation. The proposed models have been tested on three common Iranian varieties of sunflower seeds and their kernels namely Azargol, Shahroodi and Fandoghi. The results showed that rupture forces for both sunflower seed and kernel decreased with increasing moisture content, while in both loading orientations and for all varieties and size categories, the absorbed energy and deformation at rupture point increased as moisture content increased. The required compressive forces in both orientations, to initiate sunflower seed hulls rupture were higher (30.06 – 117.46 N) than those required to rupture the kernels (11.64 – 39.98 N). The seeds required lower dehulling compressive force when loaded under horizontal orientation than vertical orientation. However, an opposite trend was observed for the kernels. The deformation of kernels was substantially higher (1.92 – 2.90 mm) than the seeds (0.47 – 1.66 mm) for all variables.

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