Canola, a widely cultivated crop derived from rapeseed, undergoes a multi-stage processing journey to yield two primary products: canola oil and canola meal. This transformation is necessary to separate the valuable oil from the seed and render both the oil and the remaining meal suitable for various applications, including human consumption and animal feed.
Preparing Canola Seeds
Canola processing begins with preparing the harvested seeds. First, seeds undergo cleaning to remove impurities like dirt, stems, pods, and foreign plant matter. This step employs screening, aspiration, and magnetic separation to safeguard equipment and maintain quality.
Following cleaning, the seeds are conditioned by heating them to soften their outer shells and adjust moisture levels, typically to around 35°C, which helps prevent shattering during subsequent steps. The conditioned seeds then pass through flaking mills, which break them into thin, uniform flakes, usually between 0.3 to 0.38 mm thick. This flaking ruptures the oil-containing cells and significantly increases the surface area, making the oil more accessible for extraction. The flakes are further cooked in steam-heated units, typically at temperatures between 80°C and 105°C for 15-20 minutes, to thermally rupture additional oil cells, reduce oil viscosity, and deactivate enzymes like myrosinase that could degrade oil and meal quality.
Extracting Canola Oil
Oil extraction begins, typically employing a two-stage approach for maximum yield. The first stage involves mechanical pressing, where cooked flakes are fed into high-pressure screw presses. These presses squeeze out a significant portion of the oil, usually between 60-75% of the total oil content. The collected oil is crude oil, and the solid residue is known as press cake, which still retains a considerable amount of oil, typically 8-18%.
The second stage, solvent extraction, recovers the remaining oil from the press cake. This process washes the press cake with a food-grade solvent, commonly hexane, which is effective at dissolving oils. The hexane-oil mixture, called miscella, is processed to separate oil from solvent through evaporation. Hexane is condensed and recycled for continuous reuse.
This method is highly efficient, recovering up to 99% of the oil and reducing the residual oil in the meal to less than 1%. While full mechanical pressing can be used as a standalone method, it typically leaves higher residual oil in the meal and is favored by specialty producers for solvent-free products.
Refining Crude Canola Oil
Crude canola oil undergoes refining to achieve a stable, palatable, and consumer-ready product. The initial step is degumming, where water or organic acids remove phospholipids and other gummy substances that can cause issues during storage. These gums are then separated.
After degumming, neutralization removes free fatty acids (FFAs), which can contribute to undesirable flavors and reduce shelf life. This is achieved by treating the oil with an alkali, like caustic soda, which reacts with FFAs to form soaps. The resulting soapstock is then separated from the oil.
The next stage is bleaching, where the oil is treated with activated clays to adsorb pigments, residual soaps, and other impurities, improving the oil’s color and stability. This process is conducted under vacuum to minimize oxidation. The final step is deodorization, involving steam distillation under high temperature and vacuum. This process removes volatile compounds responsible for undesirable odors and flavors, ensuring the oil has a neutral taste and extended shelf life.
Processing Canola Meal
After oil extraction, the remaining solid material is processed into canola meal, a valuable co-product. This de-oiled press cake still contains residual solvent from the extraction process. To prepare it for use, the meal undergoes desolventizing and toasting.
Desolventizing involves heating the meal to evaporate remaining hexane, using steam-heated plates and direct steam injection. Toasting, occurring concurrently or after desolventizing, further heats the meal. This high-temperature treatment removes residual solvent and improves nutritional quality by denaturing anti-nutritional factors and enhancing protein digestibility. The toasted meal is then cooled, dried, and ground or pelleted for easier handling and storage. Canola meal is valued as a high-protein ingredient in animal feed for livestock like dairy cows, pigs, and poultry, due to its balanced amino acid profile.