Canola is one of the most important oilseed crops in the world. The oil from the seed has gained an excellent reputation for its nutritional qualities in the human diet and is the most important component of the seed in terms of market value. The meal is an important source of protein in animal feeding.
Canola Oil Plant Seed Extraction
Seed Grading and Cleaning for Canola Oil Plant
Seed delivered to the extraction plant from the farm is graded according to a strict grading standard for canola established by the Canadian Grain Commission. Payment is based on grade.
It is the first step to help ensure that a quality oil and meal are obtained. The graded seed is then cleaned to remove plant stalks, grain seeds and other materials from the bulk of the seed. Aspiration, indent cleaning, sieving, or some combination of these are used in the cleaning process.
Dehulling of the seed is, at present, not a commercial process.
Seed Preparation for Extraction for Canola Oil Plant
In many extraction plants, the cleaned seed is first heated to about 30-40ºC to prevent shattering. This is especially important with very cold seed. Some moisture adjustment may also be required. The preheated seed is then flaked on roller mills, set to very tight clearance. Usually, two sets of roller mills are used, with the second set adjusted to a tighter clearance than the first. The flaked seed is then heated to about 75-100ºC in cookers. These may be either vertical tanks with agitated, steam-heated trays or, in more modern plants, horizontal, rotary kilns equipped with steam coils.
This heating, also called cooking or conditioning, serves several very important functions: it ruptures remaining intact cells to release oil, coalesces small oil droplets to larger ones, coagulates protein for better diffusion during solvent extraction, and adjusts the moisture content of the seed prior to solvent extraction.
Another very important function of the cooking operation is to control enzymatic activity in the flaked seed, which depends on temperature and moisture content. Two enzyme systems are of importance: myrosinase, which hydrolyzes glucosinolates; and lipases, which hydrolyze triglycerides and phosphatides. These hydrolysis processes must be suppressed to produce quality oil and meal. Glucosinolate breakdown products impair the quality of the oil and the meal; triglyceride and, especially, phosphatide breakdown products make the oil more difficult to refine. A small concentration of breakdown products is usually unavoidable.
