You keep hearing the term ‘Cold Pressed’ Oils and could be wondering how they are different from the oils available in the market.
Today we will explain in detail, the difference between the different methods of oil extraction, namely, solvent extraction, expeller extraction and cold pressed extraction. Eventually you would know why we insist on Cold Pressed oils and how they are superior.
Solvent Extracted Process
In this process, before the oil is taken out of the oilseed, the seeds are ground up into a paste. These ground up seeds are then washed with a chemical (solvent), usually hexane (a petroleum distillate), to release the fat in the seed.
Now this solvent needs to be removed from the oil. So, it is then “flashed off” by heating the oil in a sealed chamber. The oil/solvent blend is heated to roughly 100˚ C, so that the solvent can be separated out. Now theoretically, this method shouldn’t leave any residue of solvent behind, but in actuality, it does leave a small part behind.
Finally the oil is then bleached and deodorized in order to remove any smell of solvent that may remain in the oil. The oil extraction efficiency is about 97-99% with this method and hence the oils made using this method are the cheapest.
Now there are two downsides of this process. One, it uses a chemical, that too a petroleum based chemical to extract the oil, which also may be leaving a small residue behind. And you know how bad petroleum based products are for us. Exposure to hexane, is known to cause dermatitis and CNS depression – depending upon the quantity of hexane inhaled or ingested, by some studies.
Second, there is huge amounts of heat involved, which oxidizes the oil, hence stripping it off its nutrient value. Heating it to such high temperatures alters the properties of the oil molecules in unfavourable ways (Polycyclic Aromatic Hydrocarbons are formed at high temperatures which are carcinogenic (Cancer causing)).
Expeller Pressed Process
In this method, no chemical is used, but instead a large press is used to physically squeeze out the oil from the seed.
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 60-99˚ C. So technically, this process is not “cold pressed”.
Expeller pressing gets out about 87-95% oil, and thus it is more expensive than the cheapest, solvent extracted oil.
Again, due to the high heat that is formed in the expeller, there is bound to be oxidation of oil and also an alteration in the properties of the oils molecules, hence leading to formation of carcinogenic (cancer causing) traits.
Further, after expelling the oil, many manufacturers add preservatives to the oil to increase their shelf life.
Cold Pressed Process
The third and final process of oil extraction is Cold Pressed Process. According to standards, cold pressed oils are to be expelled at temperatures below 50˚ C, usually done at 27˚ C.
In olden times, a long cylindrical contraption called a “ghani” was used. The oilseeds were placed inside and ground with a pestle until the oil came out. This is the simplest method for “cold-pressing” the oil out of a seed because it doesn’t involve the generation or addition of heat.
Today, there are many methods of cold press oil extraction, depending on the part of the plant oil is being extracted from. 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 50˚ C.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.
Cold pressed oils extraction efficiency is usally about 60-70% only, making them the most expensive of the lot.
Cold pressed oils are not subject to heat or chemicals, hence making them the safest of them all.
So the next time you buy your carrier oils, make sure you buy only Cold Pressed Oils. The ones which are not labeled Cold Pressed may be expeller processed or solvent extracted.