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An almost complete dehulling (hull residue lower than 3%) of sunflower seeds, before oil extraction, reduces to a minimum both the transfer of pigments from hulls to the flour and the content of fiber in the finished product. In this paper some results of our work on the dehulling of high-oil seeds with an air-jet impact huller are presented. The effectiveness of dehulling has been evaluated as a function of characteristics of the seed (variety, moisture and so forth) and of operative parameters (impact velocity, etc.). The optical analysis of the impact of the seeds on the target was made by means of high-speed cinematography (about 8000 frames/see) to have a better view of the phenomenon and to measure the parameters of energy involved. The use of proper seed monentum, which is a function of the characteristic of the seed, can allow selective hull breaking with minimum kernel breakage. Almost complete hull-free kernels from high-oil sunflower seeds were obtained by means of a continuous dehuller-separator pilot plant.

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The efficiency of an extractive system generally depends on kinetic, thermodynamic and technological parameters. Each of these factors affects the extractive effectiveness, although the overall result depends on their interaction. In the present work this interaction is analyzed for oil extraction from dehulled sunflower seed. Experiments on laboratory scale were made to calculate the kinetic and thermodynamic parameters of the extraction. The behavior of the system in 2 typical contact units (mixer‐settler and semicontinuous extractor) was studied and models assuming equilibrium conditions were formulated. The soundness of the models was checked by pilot‐plant tests and good agreement was obtained as long as the residual oil concentration in the solid was higher than ca 0.01 cso At lower oil concentrations the contact time becomes the main factor of the process, and the extraction is much less affected by the extraction ratio and the composition of the liquid.