It’s hard to know exactly what you’re getting when it comes to oil. Oils are produced in lots of different ways — some are expelled using solvents like hexane, some are expeller pressed with a mechanical press that physically squeezes the oil out.
How an oil is produced isn’t always “clearly marked” either. Sometimes the descriptors are in the title, sometimes they’re in abbreviated form (so you’ve got to know the lingo), and sometimes they’re only in the description on the spec sheet. We’ve even found that some vendors are not so adept at quality control, so sometimes you will find no mention of how the oil is made on any documents — and it will be in your hands to make sure you ask the right questions and get the proper documentation.
At Centra Foods, we always try to be as clear and explicit as possible. That’s why today, I’m going to explain what the solvent expelling, expeller pressing and cold pressing methods all look like in detail.
When explaining these processes, I’ll be referring to canola oil specifically because it’s one of the oils that’s commonly expelled in all of these different ways. However, these processes are going to look reasonably similar for many different type of seed oils (and even some other oils like olive oil). There will be some variance by mill, but this is a good baseline description to start with.
Solvent Extracted Process
Before the oil can be taken out of the oilseed, the seeds are first ground up into a paste. Next, those around up seeds a washed or purged with a solvent (also known as a petroleum distillate) such as hexane, to release the fat in the seed.
To remove that solvent from the oil, it is “flashed off” through heat in a sealed chamber. Then the oil/solvent blend is heated to approximately 212˚ F, distilling off the solvent and theoretically leaving virtually no detectable levels in the oil if the proper techniques have been applied. However, microscopic portions of up to 25 parts per million (25 ppm) of hexane can theoretically remain in the meal, which has been a point of high debate in the natural food industry.
Finally, that oil is then subject to the refining process, also known as “RBD” or Refined, Bleached & Deodorized in the industry. Some oil is also “degummed” and/or “winterized” as well. This is what makes canola oil have such a light color and flavor. It is also a similar process that occurs with soybean, sunflower, safflower, and refined olive oil.
Solvent expelling gets 97-99% of the oil out of the seed. It is the most efficient way to get all the oil from the canola seeds. That is one of the reasons that it is the cheapest canola option on the market.
Expeller Pressed Process
Expelled pressing uses a press to physically squeeze the oil out of the seed, rather than use chemicals. With this method, no solvents are used in the process, and therefore don’t have the chance of having any hexane residue left over.
An expeller press is a screw type machine which presses oil through a caged barrel-like-cavity, using friction and continuous pressure. The screw drives forward to literally squeeze the oil from the compressed seeds. There isn’t any added heat in this process, but the pressure and friction involved in the pressing process creased heat from the unit in the range of 140-210˚ F. So technically, this process is not “cold pressed”.
After the oil is removed, the remaining seed solids are left over forming a hardened cake, which is removed and later sold as meal for animal feed. Expeller pressing gets 87-95% of the oil out of the seed, so there is some oil still left over after pressing (though some claim as little as 65% is removed, so this is debated). Therefore, this option is not the cheapest, which can make this oil more expensive than the solvent expelled standard.
Expeller pressed oil is typically refined (or RBD) using the same process as described above. This refining process involves additional heat from steam and the use of a natural earthen bleaching clay.
Cold Pressed Process
Cold pressed seed oils must be produced below 122˚ F (as is legally defined in Europe) and should only apply to fully unrefined oils that are not heated later during the refining process.
The term “cold pressed” has sometimes been improperly used to describe expeller pressed oils, but these are really two different things. Cold pressing typically involves one of the following methods.
The ancient method of stone grinding or milling, as in the crushing of olive oils (quite an outdated method for any bulk EVOO production)
Bladder press extraction, which use simple compression for fruit oils such as olive and avocado. Hydraulic presses, which use simple slow compression.
Low resistance expeller pressing, which is done at a very slow rate to not exceed 122˚ F.
Modified Atmospheric Crushing (MAC) and Modified Atmospheric Packing (MAP), which employ enhanced cooling and refrigeration techniques using modified vegetable oil expeller presses that meet cold pressing temperature standards.
Remember that when related to most Extra Virgin Olive Oil, that is actually “cold spun” using a centrifuge in today’s market.
The cold pressing process typically removes the least amount from the oil from the seed, making it the least efficient and the most expensive process available.
WhIch Oils Are Most Common
In today’s market, solvent expelled canola oils are the most common. Any oils that don’t explicitly say “expeller pressed” or “cold pressed” on the bottle or the ingredient label — you can assume that these are solvent expelled.
Expeller pressed oil is the next most commonly found, though the market percentage in relation to solvent expelled oils, is miniscule. It is most often seen with the non-GMO variety of seeds — with sunflower, safflower, canola or soybean oil. It is also available in conventional oils too. For example, you can find a traditional GMO canola oil that is still expeller pressed.
Cold pressed oils are most commonly seen in the retail market, and are most often only sold as non-GMO or organic varieties (if you were going to pay for cold pressed oil for the health benefits, you’re probably the same kind of consumer that would only want to buy organic or non-GMO oils). These volumes are much smaller.
Centra Foods carries non-GMO expeller pressed canola oil, expeller pressed canola oil, and RBD conventional canola oil in bulk.