Understanding Oil Extraction Methods:

Expeller Pressed vs. Solvent Extracted Oils

Expeller pressing is the method of extracting oil with a mechanical press rather than utilizing a chemical extraction process. There are no solvent (chemical) residues in oil that has been expeller pressed resulting in a cleaner more pure oil, higher in natural colors and flavors. The process of extraction is the critical quality difference between oils often found in the natural foods marketplace as opposed to mass market or supermarket brands.

An expeller press is a screw type machine, which presses oil seeds through a caged barrel-like cavity. This machine uses friction and continuous pressure from the screw drives to move and compress the seed material. The oil seeps through small openings that do not allow seed fiber solids to pass through. Afterward, the pressed seeds are formed into a hardened cake, which is removed from the machine. Pressure involved in expeller pressing creates heat in the range of 140-210º F (60-99º C).

Solvent extraction is achieved through the grinding of seed. The ground seed or cake is then purged or washed with a petroleum distillate (the most common chemical used is hexane) which releases the oil in the seed. The solvent is then “flashed off” by heating the oil in a sealed chamber. The oil/solvent blend is next heated to 212º F (100º C) to distill off the solvent. This process theoretically leaves virtually no detectable levels of solvent in the oil if the proper techniques have been applied. However, microscopic portions (up to 25 parts per million) of hexane can remain in the meal and the finished oil. Commercial oil companies claim hexane is completely removed in the recovery phase of the extraction cycle. However, this cannot be guaranteed as manufacturing practices and quality control standards vary enormously from processor to processor.

The majority of vegetable oils sold as bottled product or food ingredient in the mass market or conventional food industry are solvent extracted oils. Mass market oils, however, are not required to be labeled as solvent extracted. The main reason for using solvent extraction is largely economic as the greater efficiencies of solvent extraction maximizes yields and profits. This is why solvent extraction has evolved into the most common form of oil removal – it delivers the least expensive and subsequently the lowest quality vegetable oils.


Expeller Pressed vs. Cold Pressed Oils

All cold pressed oils are expeller pressed. But all expeller pressed oils are not necessarily cold pressed. It all has to do with temperature.


What is Expeller Pressing?

Expeller pressing is a chemical-free mechanical process that extracts oil from seeds and nuts. This method of oil extraction is an alternative to the hexane-extraction method used for many conventional oils. The temperature reached during pressing depends on the hardness of the nut or seed. The harder the nut or seed, the more pressure required to extract the oil, which in turn creates more friction and higher heat. There is no external heat applied during the expeller pressing


Why Cold Press?

Delicate oils, or those in which flavor nuances are a key component, need to be treated with greater care in controlling processing factors. Oils that are cold pressed are expeller pressed in a heat-controlled environment to keep temperatures below 120 degrees F.

    
Refined or Unrefined?

All of Spectrum's refined oils are processed using natural processes, without any harsh chemicals or contaminants. The decision of which Spectrum oil to buy really depends on what you plan to use the oil for and your preference in taste.

Unrefined oils are just that—left in their virgin state after pressing. These oils tend to be rich, robust and ‘true' in their flavors. Take Spectrum's Peanut Oil for example—it quite literally smells and tastes just like fresh roasted peanuts. Or Spectrum's Unrefined Coconut Oil, which has an aroma so pure it transports you to the tropics.

Unrefined oils are also much richer in nutrients. For instance, the peppery tingle from unrefined olive oil comes from antioxidant-rich polyphenols which are largely destroyed during any kind of refining.

The drawback to unrefined oils is they have a lower smoke point than refined oils. Refined oils, oils that have had impurities filtered out, can stand a much higher heat on the stove. So High Heat Canola Oil would be a more appropriate choice for a stir fry or high heat sauté than Organic Tuscan Olive Oil.


Here are some bottom-line bullets to help you choose wisely:

- For culinary oils, choosing a refined or unrefined oil is a matter of taste and what you'll use it for in the kitchen.
- Choose unrefined oils for fullest flavor and highest nutrient content.
- Choose refined oils for high heat uses.
- For refined oils, choose those that have been refined without chemicals.


References:

<a href="http://spectrumingredients.com/product/gen_info/oil_extract.html">Understanding Oil Extraction Methods</a>

<a href="http://www.spectrumorganics.com/?id=32">Expeller Pressed vs. Cold Pressed</a>

<a href="http://www.spectrumorganics.com/?id=35"> Refined or Unrefined?</a>