Mechanical stress on canola seed during dehulling

The mature canola seed comprises an embryo, a group of structures that have a high content of protein and oil, and a fibrous seed coat held together by endosperm tissues. High-quality canola meal production requires removal of fiber-rich seed hull that typically contributes little nutrient value. Canola hull accounts for more than 70.0% of the insoluble fiber within the seed, which limits its uses as feed. Dehulling canola seed, before oil extraction, increases the protein content and decreases fiber content in the meal, to up to 50.0% and to down to 10.0%, respectively. Due to the complexity in dehulling canola seeds, several methods have been explored by the canola processing industry. However, little research has been conducted in analyzing the effects that mechanical dehulling methods have on seeds. In this study, we conducted mechanical tests to characterize seed behavior and hull fracture under uncoupled stresses such as compression and shear;stresses generated by the common dehulling equipment used in the industry, such as mills. All tests were carried out on single seeds at different moisture contents, from 5.00% to 25.0% wet mass basis (w.b.). Over a range of moisture contents studied, shear loading mode limited deformation of embryos in comparison to compression loading. Additionally, hardness tests were performed with a nano-indenter machine to determine seed hull properties. The overall results from these experiments provided information used to construct a computational model that represents canola seed deformation under compression stress.