Design of a new canola dehulling process to produce high-quality meals

Canola is typically used for oil extraction due to its high oil content of edible oil. However, canola can be processed to produce high-protein meal suitable for livestock feed and food applications. To produce high-quality canola meal the seed hull must be removed, as this fraction is typically rich in insoluble fiber and contributes little nutrient value. Dehulling canola seed is a challenging task compared to other oil seed, as canola seed has physical properties such as small size (~2mm in diameter), a spherical shape, thin hull (< 50µm), and a tight connection between embryo and hull. Despite advances in technology and oil extraction methods, there is no efficient method reported for dehulling canola that could be scaled to industrial mass production.

The objective of this study was to propose and assess a novel front-end mechanical dehulling approach that applies shear stress to the seed using rollers. Additionally, we tempered the seed using a fluidized bed drying process prior to dehulling, which aids in the separation of the hull from the embryo. Subsequent assessment of seeds after tempering was conducted using non-destructive micro-computed tomographic (micro-CT) imaging. Embryos of seed tempered with the fluidized bed drying method shrank, detaching the hull and embryo. Using the axiomatic design methodology, we established parameters for machines that could produce a high yield of clean embryos and hulls.

Our analysis found that the hull fraction presented less than 10% contamination from the embryos. We conclude that the combination of fast fluidized drying and shear dehulling results in high yields of clean fractions (hulls and embryos). As such, the technique proposed in this study holds significant promise for industrial-scale canola dehulling.