How Vegetable Oils are Processed

by Jade Shutes

Use Live Oils! “Live oils are oils which still have their nutritional content, especially Essential fatty acids (EFAs), intact. This means oils which have not been exposed to excessive heat, light, oxygen and reactive metals during processing. This means oils that have not been extracted using chemicals or hexane.” Omega Nutrition

The process of refining oils is exactly analogous to the refining of whole wheat and whole sugar into white ones. In all cases, one takes a product full of natural vitamins, minerals, enzymes and other food factors and reduces the original natural food into a relative “non-food”—devitalized, stripped.
(Mother Earth News)

Learn more about vegetable oils in our “About Vegetable Oils” E-Book

The quality of the base oil which you utilize is as important as the quality of essential oils. The following are explanations of commonly used processing in the extraction of vegetable oils. Glossary of terms as defined by the Natural Products Quality Assurance Alliance (NPQAA) Quality and Safety Standards July 12, 1995. The NPQAA is in the process of establishing standards for the health food industry in the USA. This information was obtained for the EWSHAS from Omega Nutrition.

  • Bleaching & Filtering: Bleaching and filtering for refined oils use diatomaceous earth, acidified or non-acidified clay, or other absorbents to remove colors and some odors.
  • Cleaning, Hulling: Harvest trash, dust, dirt and sub-standards seeds removed. No heat or chemicals are used at this stage.
  • Cooking & Tempering: Tempering is used to lower the inherent moisture levels of seeds, permitting effective oil expelling. Cooking is used to bring seed micellar cells up to the point where pressure will permit rupturing and release of oil content. Temperature ranges for both steps are 120 – 200 degrees F or 40 – 93 degrees C.
  • Degumming: Degumming is a water washing process which uses water wash, citric acid, or phosphoric acid to remove the lecithin and phosphates. Oil and water are centrifuged out.
  • Deodorizing: Refined oil is pumped and deposited on rotating trays held in a vacuum. Steam is injected to strip volatile odors and flavors from the oil. Temperatures range from 450 – 470 F/232 – 243 C.
  • Essential Fatty Acids (EFAs): EFAs must be obtained in proper balance from food or supplements. EFAs are part of the membranes of every cell in our body. They also produce hormone like-substances necessary for energy metabolism and cardiovascular and immune health. EFAs are extremely reactive and are easily damaged by light, heat and oxygen exposure.
  • Expeller Pressing: Expeller pressing is the mechanical pressing of seeds, which removes the oil by crushing friction and pressure. Temperatures can go up to 160 F /71 C, depending on seed type, season and moisture content. Expellers can run with or without cooking and tempering but yields are significantly lower without these added steps. “Some companies list expeller pressed oil as an ingredient on labels. However, since most oils are expeller pressed, the issues that should be considered are the pressing temperatures, and if the oils are subsequently refined and deodorized at temperatures up to 450 – 470 F/232 -243 C.” Omega Nutrition
  • Filtering: Mechanical filtering is used to strain out sediment and raw material.
  • Flaking: Flaking is used to break down hard seed casings and opening the seed fibers to permit extraction of oil-bearing contents. Seed is ground and formed in a steam extruder ready extraction. Frictional heating raises the temperature to approximately 160 F/88 C.
  • Hydrogenation: Hydrogen gas is pumped through the oil while it is heated. A metal catalyst such as nickel, zinc, copper or other reactive metal is used to initiate reaction of the oil with the hydrogen. This stabilizes and hardens polyunsaturated oils. The biologically normal cis-configured fatty acids are changed with the process into trans-fatty acid in order to make the oils stable at room temperature for long periods of time, or to solidify liquid oils.
  • Refining: There are two forms of refining, alkali refining and physical refining. For the alkali refined, alkaline chemicals are added to reduce Free Fatty Acids (FFAs) and Peroxide values. Alkali is washed out along with FFAs which have saponified (turned to soapy solids). The alkali is centrifuged out with no trace of alkali left in the refined oil. Physical refining also removes FFAs and peroxides, using a modified form of steam deodorization. This method is largely used in Europe as an alternative solution to the problem with caustic and soap wastes generated by the alkali refining process.
  • Solvents: Solvents used are petroleum distillates (such as hexane) that are used to wash the remnant oil out of ground seeds. The solvents are flashed off when the oil/solvent blend is heated to 212 F/ 100 C, theoretically leaving no detectable solvent levels in the refined oil, if the proper techniques are applied. According to the commercial oil companies, hexane is completely removed, but this cannot be guaranteed, as manufacturing practices and quality standards vary enormously from manufacturer to manufacturer. Hexane also poses an environmental threat as it contributes to air pollution.
  • Cis-fats: Polyunsaturated fats have carbon bonds in their double chains. Cis- means both hydrogen’s are on the same side of the double bond, like the relationship between your right foot and right hand, with your trunk as the double bond. In the cis- form, the chains kink into a spiral structure and don’t crystallize at room temperature. They are also reactive, oxidizing and turning rancid relatively quickly. However, its spirality, reactivity and fluidity are essential for the proper functioning of biological systems. Cis-fats are almost exclusively the type of fat found naturally in living organisms.
  • Trans- Fats: When polyunsaturated fats are partially hydrogenated or heated to temperatures above 320 F/ 120 C, the cis- version switches to trans – and the chain unkinks. The fat becomes solid – hence usable for baking – and very inert. Trans- fats cannot be used to construct properly functioning biological tissues.
  • Winterizing: Cloudiness is removed by chilling and filtering. Used for cold pressed vegetable oils naturally high in waxes and stearins. Temperatures are around 45 Fahrenheit or 7 Celsius.

“Refined oils are heated, deodorized and have many valuable nutrients removed. The vitamin E that is present in unrefined oils is taken out and sold to the vitamin industry. The lecithin that helps your body emulsify and use fats more effectively is removed. The result is a naked oil that is nearly devoid of nutritional value.” Robert Crayhon

“Light is the greatest enemy of all vegetable oils. All unsaturated oils such as flaxseed and other polyunsaturated oils, have a strong absorption of light that rises dramatically in the visible green light wavelengths. The more nutritious the oil, the more vulnerable it is to degeneration. Strong absorption of green, blue, violet and ultraviolet light indicates that a great deal of energy is transferred to the oil. This energy manifests itself in rapid, irreversible chemical reactions called photo-oxidation. Any exposure to sunlight or interior lighting, especially fluorescent, can cause immediate reactions. Prolonged exposure to light will eventually turn an oil ‘rancid’, regardless of whether an oil is in a sealed container.” Dr. C. Leigh Broadhurst

For further information:

The Dangers of Vegetable Oil Extraction and Processing