Green canola seed usually has issues other than just high chlorophyll
levels. Canola delivered with high levels of green seed was probably
swathed immature or was frozen before it had a chance to fully cure.
Therefore canola with high green seed content also tends to have smaller
seeds, more damaged seeds and a lower overall oil content per ton of
High amounts of green chlorophyll in the seed also increase the processing cost because that chlorophyll must be removed to produce the
light-colored oil customers expect.
Processors use a clay filtration process to remove chlorophyll.
Natural clay particles—“Fuller’s earth” or “montmorillonite clay” used
specifically for their high adsorption qualities—are added to the oil. Inter-
estingly, these same clays are used to clarify wine. Chlorophyll molecules
bond with the clay particles. The clay is then filtered, taking the chloro-
phyll with it. Canola oil with higher chlorophyll content will require more
clay and possibly more passes with the clay to remove that chlorophyll,
adding to the cost required to clarify the oil. “All canola oil gets the clay
treatment, but the more chlorophyll, the more clay and cost required for
that step,” says Dave Thiessen, edible oils facility manager with Bunge in
Altona, Manitoba, Canada.
Adel Ghabour, quality
assurance manager with
Richardson Oilseed in Lethbridge, Alberta, Canada,
adds that the more clay
used to remove color, the
more oil that is lost in the
process. “Oil is trapped
within gaps in the clay, and
that oil is not recovered
unless the clay goes back
through the extractor,”
Green seed, heated seed, moisture, and dockage all add costs to canola processing, which is why
seed delivered with high amounts of any of these factors will fetch a lower price. The bottom line
is that top-grade canola with low dockage moves through crushing plants more efficiently.
Adel Ghabour, quality assurance manager with
Richardson Oilseed, explains the key steps in canola
processing at CanoLAB in Olds, Alberta, Canada.