Canola oil is made by crushing canola seeds, extracting the oil using mechanical pressure and a chemical solvent, then refining the crude oil through several stages to produce the clear, neutral-tasting product you find on store shelves. The full process involves cleaning, pressing, solvent extraction, degumming, bleaching, and deodorizing. It’s more industrial than most people expect.
Canola Starts as a Specially Bred Seed
Canola isn’t a naturally occurring plant. It was developed in the 1970s through classical breeding of rapeseed, which historically contained high levels of erucic acid (a fatty acid linked to heart damage in animal studies) and bitter compounds called glucosinolates. Breeders in Canada created “double-low” varieties with more than 95% less erucic acid and 70% to 90% fewer glucosinolates than traditional rapeseed. The first cultivar, called Tower, was released in 1974.
To legally be called canola oil, the product must contain no more than 2% erucic acid, per FDA regulations. The name “canola” essentially means food-grade rapeseed oil that meets this threshold.
Cleaning, Crushing, and Pressing
At the processing plant, canola seeds are first cleaned to remove stems, dirt, and other debris. The seeds are then conditioned with mild heat to make them easier to work with, and they’re flaked between rollers to break open the cell walls. This flaking dramatically increases the surface area, which helps release oil more efficiently.
The flaked seeds go through a mechanical screw press, sometimes called an expeller press. This machine physically squeezes oil out of the seed material using intense pressure. Friction from the press generates heat, typically pushing temperatures to between 140°F and 210°F. This first pressing recovers a significant portion of the oil, but not all of it. About 42% of a canola seed’s weight is oil, and the remaining solid material, called press cake, still holds a meaningful amount.
Solvent Extraction With Hexane
To capture the oil left behind in the press cake, manufacturers turn to a chemical solvent called hexane. The press cake is broken into flakes, ground up, and mixed with hexane to create a slurry. This mixture is heated, causing the hexane to evaporate and pull oil out of the seed material as it does. The remaining oil releases from the meal during heating and mixes with residual hexane.
The oil-hexane mixture is then distilled to separate the two. The hexane is collected and recycled for reuse. This solvent extraction step is what makes industrial canola oil production so efficient: virtually all the available oil gets recovered from the seed. The leftover solid meal, now stripped of its oil, contains roughly 36% to 40% protein and is sold as livestock feed for poultry, pigs, and cattle. Processing a batch of canola seed yields approximately 42% oil and 58% meal.
Refining: Degumming, Bleaching, and Deodorizing
The crude oil that comes out of extraction is dark, strong-smelling, and contains impurities. It goes through three main refining stages before it’s ready for your kitchen.
Degumming removes phospholipids and other gummy substances by mixing the oil with water or an acid solution, which causes the gums to clump together so they can be separated out.
Bleaching isn’t about color alone. The oil is mixed with absorbent clays that pull out pigments, oxidation byproducts, and trace metals. The clay binds to these impurities and is filtered out, leaving a lighter, cleaner oil.
Deodorizing is the final and most intense step. The oil is heated to temperatures above 200°C (as high as 235°C, or 455°F) under vacuum while steam is injected through it. This strips out volatile compounds like free fatty acids that give the crude oil its strong taste and smell. Steam works as the stripping agent because it’s cheap and effective at carrying away unwanted volatiles at low pressure. The result is the bland, shelf-stable oil consumers expect.
What Happens to the Oil During Deodorization
The deodorization stage does change the oil slightly. Exposure to temperatures above 200°C causes a small portion of the unsaturated fatty acids, particularly omega-6 and omega-3 fats, to convert into trans fat isomers. Commercial canola oil typically contains between 1.9% and 3.6% trans fats as a result, according to analyses of multiple samples. This is far less than you’d find in partially hydrogenated oils (which are now largely banned), but it’s not zero. All deodorized vegetable oils contain trace trans fats for the same reason.
The trans-isomers of linolenic acid (an omega-3 fat) are the most affected, potentially reaching up to 3% of total fatty acids. The omega-6 linoleic acid isomers are lower, typically between 0.2% and 1.0%. These amounts are small enough that canola oil can still be labeled as containing zero grams of trans fat per serving under FDA rounding rules.
Cold-Pressed and Expeller-Pressed Alternatives
Not all canola oil goes through solvent extraction and high-heat refining. Cold-pressed canola oil is made using only mechanical pressure, with temperatures kept below 122°F (50°C) throughout. Expeller-pressed canola oil also skips the hexane step but allows higher temperatures from the friction of the press, typically between 140°F and 210°F. Both methods yield less oil per batch than solvent extraction, which is why these products cost more.
Cold-pressed canola oil retains more of the seed’s original flavor, color, and minor nutrients that get stripped during conventional refining. It has a lower smoke point and shorter shelf life, making it better suited for dressings and low-heat cooking than deep frying. Expeller-pressed oil falls somewhere in between: no chemical solvents, but the higher friction temperatures mean it’s not quite as “raw” as cold-pressed.
From Refining to Bottle
After deodorization, conventional canola oil is essentially finished. It’s a pale yellow, neutral-tasting oil with a smoke point around 400°F, which is why it’s popular for frying and baking. The refined oil is tested for quality, filtered one final time, and packaged. The entire journey from seed to bottle involves more chemistry and engineering than most cooking oils suggest on their labels, but the end product is one of the most widely used vegetable oils in the world.