The Meaning Of Expeller Pressed vs Cold Pressed
Low resistance expeller pressing which is done at a very slow rate to not exceed 122° F.
Modified Atmospheric Crushing and Modified Atmospheric Packing which employ enhanced cooling and refrigeration techniques using modified vegetable oil expeller presses that meet cold pressing temperature standards.
Debunking The Debate Between Expeller Pressed Versus Cold Pressed Oil
When processors start comparing various oilseed extraction methods and machines, they often ask us about the difference between expeller pressed versus cold pressed oil extraction. Unfortunately, this question doesn’t quite make sense — and here’s why.
Comparing expeller pressed versus cold pressed oil equipment
What processors are really asking about is the difference between hot pressing and cold pressing. The fact that people often associate the expeller press with hot pressing indicates some confusion between extraction equipment, like the Expeller, and the extraction process, like hot or cold pressing.
In the same way that people often use brand names like Xerox or Kleenex when referring to an entire product category, the Expeller trademark has become practically synonymous with a traditional screw press — which is typically associated with hot pressed oil. However, it’s important not to confuse the equipment with the extraction method, because an Expeller can be used for either hot pressing or cold pressing, depending on your full system process.
Ultimately, processors are trying to figure out the best extraction method for their facility, so they can select the right equipment to process oil efficiently. We’ll answer this burning question below by comparing hot and cold pressed extraction techniques. But first, we’ll offer some background about the expeller press to set the records straight so that you can ask the right questions about oilseed extraction.
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History of the Anderson Expeller Press
In 1900, Anderson International’s founder, Valerius D. Anderson, invented a new way to extract oil by developing the first continuous mechanical extractor. He patented this screw press under the trademark name, Expeller®, and Anderson International Corp. began selling them to oilseed processors around the world.
Initially, heat was not involved in the extraction process (at least, not beyond the frictional heat created by the mechanical screw press). Heat was added to the process later, in the 1910s, when Anderson discovered that cooking and drying the oilseed prior to extraction could make the pressing operation more efficient. This led to the development of Anderson’s line of extruders, cookers, dryers, and other specialized equipment that cooks and dries oilseed using steam heat and friction.
We’ll explain the benefits of adding heat to this process in the next section, but it’s important to remember that the Expeller press itself isn’t adding heat. Heat is added separately through dedicated upstream equipment like the Extruder, so trying to compare Expeller pressed versus cold pressed oil isn’t really an accurate comparison. It’s like comparing a Xerox to a color copy, when in fact, a Xerox machine can make color copies, too.
Now that you understand why the comparison is really between hot pressed and cold pressed oil, we can get to the answer.
What is hot pressing?
Hot pressing is the process of adding heat to cook and dry oilseeds prior to extraction. Although these steps are often conflated into one, cooking and drying are actually two separate processes that each serve a valuable purpose to prepare raw material for more efficient pressing downstream.
Cooking: In the first step, heat is applied to cook the oilseeds at a constant temperature and moisture —breaking down the material at the microscopic level using heat to release the oil trapped inside. This process traditionally used indirect steam heat vessels to maintain the oilseeds at a constant and elevated temperature, making the oil easier to extract.
Moisture is a critical element of the cooking process because it helps transfer heat more evenly and efficiently. At this point in the process, oilseeds typically have a moisture level between 10-12%. However, that moisture will make it harder for the press to operate downstream because it over-lubricates and even clogs the equipment. For this reason, it’s critical to remove the moisture after cooking by using — you guessed it — more heat.
Drying: After the cooking process, heat is added in a second step to dry the oilseeds — essentially removing excess moisture to prepare the material for more efficient pressing. Generally, material should be dried to less than 5% moisture content before heading to the press. The Anderson Expeller, for instance, processes most efficiently when material contains between 3-5% moisture.
Traditionally, oilseed processers used stacked batch cooking and drying vessels to generate steam heat for these added steps. Alternatively, the Anderson Dox™ (Dry Oilseed Extruder) replaces expensive steam-heated cooking vessels with mechanical energy to more efficiently cook and dry oilseeds ahead of the Expeller.
Regardless of the equipment used upstream, adding heat prepares the oilseed for more efficient pressing by rupturing the cells to release the oil, so it flows more freely through the Expeller.
What is cold pressing?
Cold pressing, by comparison, does not add heat to cook and dry the oilseed before extraction. Instead of using traditional steam vessels or extrusion systems to cook and dry the oilseeds, cold pressing skips these steps by sending raw material straight to the Expeller press.
Since this “cold” material hasn’t been cooked or dried to release the oil from the seeds, the screw press has to work even harder to extract the oil with pressure alone. This calls for more torque to squeeze the oilseeds harder and longer. Some processors achieve this by running multiple presses or multiple passes through the same press, which can be very inefficient. The Anderson Super Duo Expeller® utilizes two presses in a single pass to extract oil more efficiently, making it ideal for cold pressing.
But just because there’s no external heat added in cold pressing doesn’t necessarily mean there’s no heat involved. Heat often sneaks into the process early on, to dry the raw oilseed material for storage, and later on, through the form of friction in the press.
Drying Oilseeds for Storage: Keep in mind that whether you’re hot pressing or cold pressing oil, you still need to dry your raw oilseed material for safe storage beforehand. This is different from the drying step we just discussed, which uses heat to dry the cooked material to less than 5% moisture content immediately before extraction in a traditional hot press.
Drying oilseed for storage is a critical first step because if your material isn’t stored at the proper moisture level (below 12%), you risk losing it all to mold, mildew, and bacterial growth before you can even begin processing. Whether you proceed to hot pressing or cold pressing, you’ll always start by drying your material for storage. However, in the case of cold pressing, you won’t add heat to further dry the oilseed again before extraction.
Combating Friction in the Press: As with the original Expeller, the mechanical motion of the screw press naturally creates some frictional heat, even in cold pressing. In fact, with more torque comes even more friction. Cold presses must compensate for this heat by using a water-cooled shaft to keep the press cool during the process. Then, as oil is expelled from the press, it’s pumped through a heat exchanger to instantly drop the temperature of the oil and keep it cool.
Cold-pressed or “virgin” oils often demand a premium price in the market compared to traditional hot pressed oils, which can make cold pressing an attractive option to improve profits.
In summation
An expeller press can become a hot press or a cold press, depending on the steps you take upstream before extraction. Equating an expeller with hot pressing isn’t quite accurate because the screw press has nothing to do with the processing temperature. Whether you’re adding heat to cook and dry oilseed for hot pressing, or minimizing heat through cold pressing, you can achieve optimal efficiency for your facility when you have the right equipment for the job.
Now, instead of asking about the differences between expeller pressed versus cold pressed oil, you understand how to compare hot pressing and cold pressing — using an expeller either way to extract the oil trapped inside.
To learn more about oilseed extraction methods and machinery, contact the experts at Anderson International.
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The Meaning Of Expeller Pressed vs Cold Pressed
It can be hard to know exactly what you may be getting when it comes to oil. Oils are produced in multiple ways. Some are expelled using solvents like hexane, while others are expeller-pressed with a mechanical press that squeezes the oil out.
How the oil is produced isn’t always clearly marked either. Sometimes it is described in the title, in full works or abbreviated form, or sometimes you might find that it is only described on the spec sheet. Worse still, some industrial suppliers make no mention of how the oil is made on any documents. It will be in your hands to make sure you ask all the right questions and receive the proper documentation.
Here at Centra Foods, we make it a point to be as clear and explicit as possible. That is why today I will explain what solvent expelling, expeller pressing and cold pressing methods all look like in detail.
While explaining these processes I’ll be referring to canola oil specifically because it’s one of the oils commonly expelled in all of these different ways we will discuss. These processes are going to look reasonably similar across many different types 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 seed, the seeds are first ground up into a paste. Next, those ground-up seeds are washed or purged with a solvent such as hexane to release the fat in the seed. The solvent may also be known as petroleum distillate.
The removal of that solvent from the oil is done by flashing using high heat in a sealed chamber. The oil/solvent blend is heated to approximately 212° Fk, 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 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 subjected to the final refining process also known as RBD or Refined Bleached and Deodorized in the industry. 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. Some oil is also de-gummed and/or winterized as well.
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
Expeller pressing uses a press to squeeze the oil out of the seed rather than using 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.
A press for expelling is a screw-type machine that 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 can create heat from the unit in the range of 140-210′ F. So technically this process is not cold-pressed because the oil may not stay cool, even if no heat is added.
After the oil is removed, the remaining seed solids are leftover 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. 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 using the same process as described above. This refining process involves additional heat from steam (again, exempting it from the “cold pressed” claim) and the use of a natural earthen bleaching clay.
Cold Pressed Process
Cold pressed seed oils must be produced below 122° F 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.
Bladder press extraction uses simple compression for fruit oils such as olive and avocado.
Hydraulic presses use simple slow compression.
Low resistance expeller pressing which is done at a very slow rate to not exceed 122° F.
Modified Atmospheric Crushing and Modified Atmospheric Packing which employ enhanced cooling and refrigeration techniques using modified vegetable oil expeller presses that meet cold pressing temperature standards.
Most Extra Virgin Olive Oil that is called “cold pressed” is actually “cold spun” using a centrifuge in today’s modern processing systems.
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 Are The Most Common Oils
In today’s market solvent expelled canola oils are the most common by far. For any oils that don’t explicitly say “expeller pressed” or “cold pressed” on the bottle or 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 minuscule. It is most often seen with the non-GMO variety of seeds with sunflower, safflower, canola, and soybean oil. It is also available with conventional oils too. For example, you can find traditional GMO canola that is still expeller pressed.
Cold-pressed oils are mostly seen in the retail market and are often only sold as non-GMO or organic varieties. These volumes are much smaller.
