Cooking oil extraction and refinement[edit]

Olive oil production inCroatia

Cooking oil extraction and refinement are separate processes. Extraction first removes the oil, typically from a seed, nut or fruit. Refinement then alters the appearance, texture, taste, smell, or stability of the oil to meet buyer expectations.


There are three broad types of oil extraction:

  • Chemical solvent extraction, most commonly using hexane.
  • Pressing, using an expeller press or cold press (pressing at low temperatures to prevent oil heating).
  • Decanter centrifuge.

In large-scale industrial oil extraction you will often see some combination of pressing, chemical extraction and/or centrifuging in order to extract the maximum amount of oil possible.[39]


Cooking oil can either be unrefined, or refined using one or more of the following refinement processes (in any combination):

  • Distilling, which heats the oil to evaporate off chemical solvents from the extraction process.
  • Degumming, by passing hot water through the oil to precipitate out gums and proteins that are soluble in water but not in oil, then discarding the water along with the impurities.
  • Neutralization, or deacidification, which treats the oil with sodium hydroxide or sodium carbonate to pull out free fatty acids, phospholipids, pigments, and waxes.
  • Bleaching, which removes "off-colored" components by treatment with fuller's earth, activated carbon, or activated clays, followed by heating, filtering, then drying to recoup the oil.
  • Dewaxing, or winterizing, improves clarity of oils intended for refrigeration by dropping them to low temperatures and removing any solids that form.
  • Deodorizing, by treating with high-heat pressurized steam to evaporate less stable compounds that might cause "unusual" odors or tastes.
  • Preservative addition, such as BHA and BHT to help preserve oils that have been made less stable due to high-temperature processing.

Filtering, a non-chemical process which screens out larger particles, could be considered a step in refinement, although it doesn't alter the state of the oil.

Most large-scale commercial cooking oil refinement will involve all of these steps in order to achieve a product that's uniform in taste, smell and appearance, and has a longer shelf life.[39] Cooking oil intended for the health food market will often be unrefined, which can result in a less stable product but minimizes exposure to high temperatures and chemical processing.

Waste cooking oil[edit]

A bin for spent cooking oil inAustin, Texas,USA, managed by a recycling company.

Proper disposal of used cooking oil is an important waste-management concern. Oil is lighter than water and tends to spread into thin and broad membranes which hinder the oxygenation of water. Because of this, a single litre of oil can contaminate as much as 1 million litres of water.[citation needed] Also, oil can congeal on pipes provoking blockages.[40]

Because of this, cooking oil should never be dumped in the kitchen sink or in the toilet bowl. The proper way to dispose of oil is to put it in a sealed non-recyclable container and discard it with regular garbage.[41] Placing the container of oil in the refrigerator to harden also makes disposal easier and less messy.


Main article: Vegetable oil recycling

Cooking oil can be recycled. It can be used as animal feed, directly as fuel, and to produce biodiesel,[42] soap, and other industrial products.

In the recycling industry, used cooking oil recovered from restaurants and food-processing industries (typically from deep fryers or griddles) is called recycled vegetable oil (RVO), used vegetable oil (UVO), waste vegetable oil (WVO), or yellow grease.[43]

Yellow grease is used to feed livestock, and to make soap, make-up, clothes, rubber, detergents, and biodiesel fuel.[44][45]

Used cooking oil, besides being converted to biodiesel, can be used directly in modified diesel engines and for heating.

Grease traps or interceptors collect fats and oils from kitchen sinks and floor drains which would othewise clog sewer lines and interfere with septic systems and sewage treatment. The collected product is called brown grease in the recycling industry.[43] Brown grease is contaminated with rotted food solids and considered unsuitable for re-use in most applications.


Gutter oil and trench oil are terms used in China to describe recycled oil processed to resemble virgin oil, but containing toxic contaminants and sold illegally for cooking; its origin is frequently brown grease from garbage.[46]

In Kenya, thieves sell transformer oil stolen from electric transformers to operators of roadside food stalls for use in deep frying, suitable for prolonged use longer than regular cooking oil, but a threat to consumer health due to the presence of PCBs.[47]


  1. Jump up^ The smoke point of an oil depends primarily on its free fatty acid content (FFA) and molecular weight. Through repeated use, as in a deep fryer, the oil accumulates food residues or by-products of the cooking process, that lower its smoke point further. The values shown in the table must therefore be taken as approximate, and are not suitable for accurate or scientific use.[26][27]
  2. Jump up^ The smoke point of margarine varies depending on the types of oils used in its formulation, but can be generally assumed to be similar to that of butter.[citation needed]


Refined vegetable oil starts from the seeds of various plant sources. The fats from plant seeds are polyunsaturated, meaning they remain in a fluid state at room temperature.

There are many different kinds of commercially refined vegetable based oils, including canola or rapeseed oil, soybean oil, canola oil, corn oil, sunflower oil, safflower oil, and peanut oil.

The generic cooking term "vegetable oil" refers to a blend of a variety of oils often based on palm, corn, soybean or sunflower oils.

Refined cooking oils are made by highly intensive mechanical and chemical processes to extract the oil from the seeds. This process removes the natural nutrients from the seeds and creates a final product which oxidizes easily. The oxidation factor makes these oils more likely to break down into cancer causing free radicals within the body.

In addition, many refined vegetable oils are also hydrogenated. This hydrogenation process makes them solid at room temperature so they can be sold as margarine and shortening. This hydrogenation process further damages the fatty acids in the oils, creating trans fatty acids, which are particularly dangerous to human health.

The consumption of vegetable oils created through chemical extraction processes is linked to widespread inflammation within the body, elevated blood triglycerides, and an impaired insulin response. These oils have been linked to diabetes, cancer and heart disease in multiple studies.

The Process of Extracting Vegetable Oil

The process of extracting vegetable oil from oil seeds is not for the squeamish. Take a look at the steps and decide for yourself if this is a "food" you want to consume:

  1. Oil seeds such as soybean, rapeseed, cotton, sunflower are gathered. Most of these seeds are from plants that have been genetically engineered to resist the huge amounts of pesticides applied to them.
  2. The seeds are husked and cleaned of dirt and dust, then crushed.
  3. The crushed seeds are then heated to temperatures between 110 degrees and 180 degrees in a steam bath to start the oil extraction process.
  4. The seeds are put through a high volume press which uses high heat and friction to press the oil from the seed pulp.
  5. The seed pulp and oil are then put through a hexane solvent bath and steamed again to squeeze out more oil.

    Note: Hexane is produced by the refining of crude petroleum oil. It is a mild anesthetic. Inhalation of high concentrations produces first a state of mild euphoria, followed by sleepiness with headaches and nausea. Chronic intoxication from hexane has been observed in recreational solvent abusers and in workers in the shoe manufacturing, furniture restoration and automobile construction industries where hexane is used as a glue. The initial symptoms are tingling and cramps in the arms and legs, followed by general muscular weakness. In severe cases, atrophy of the skeletal muscles is observed, along with a loss of coordination and problems of vision. In 2001, the U.S. Environmental Protection Agency issued regulations on the control of emissions of hexane gas due to its potential carcinogenic properties and environmental concerns.

  6. Now the seed/oil mixture is put through a centrifuge and phosphate is added to begin the separation of the oil and seed residues.
  7. After solvent extraction, the crude oil is separated and the solvent is evaporated and recovered. The seed pulp residues are conditioned and reprocessed to make by-products such as animal feed.
  8. The crude vegetable oil is then put through further refining techniques including degumming, neutralization and bleaching:
    • Water degumming: In this process, water is added to the oil. After a certain reaction period the hydrated phosphatides can be separated either by decantation (settling) or continuously by means of centrifuges. In this process step a large part of water soluble and even a small proportion of the non-water soluble phophatides are removed. The extracted gums can be processed into lecithin for food, feed or for technical purposes.
    • Neutralization: Any free fatty acids, phospholipids, pigments, and waxes in the extracted oil promote fat oxidation and lead to undesirable colors and oders in the final products. These impurities are removed by treating the oil with caustic soda (sodium hydroxide) or soda ash (sodium carbonate). The impurities settle to the bottom and are drawn off. The refined oils are lighter in colour, less viscous, and more susceptible to oxidation. Hmmm, lucky for us.
    • Bleaching: The major purpose of bleaching is the removal of off colored materials in the oil. The heated oil is treated with various bleaching agents such as fuller's earth, activated carbon, or activated clays. Many impurities, including chlorophyll and carotenoid pigments, are absorbed by this process and removed by filtration. However, bleaching also promotes fat oxidation since some natural antioxidants and nutrients are removed along with the impurities.
  9. Deodorization is the final step in the refining of vegetable oils. Pressurize steam at extremely high temps (500 degrees or more) is used to remove volatile compounds which would cause off odors and tastes in the final product.

    The oil produced is referred to as "refined oil" and is ready to be consumed or for the manufacture of other products. A light solution of citric acid is often added during this step to inactivate any metals such as iron or copper present in the final product.

The process of refining vegetable oil damages the fats and makes the oils very unstable and prone to going rancid quite easily. Rancid oils in any form are particularly bad for your health because they introduce cancer causing free radicals into your body, without the benefit of including an antioxidant like vitamin E.


What follows is a generic description of the process involved in getting oils out of seeds (or in this case coconut copra) and onto your grocer's shelves.

Oil Milling

Copra (about 64% oil content) from the warehouse bin is fed to a belt conveyor where dirt and other foreign materials are manually removed. Metallic objects are disposed off by means of magnets strategically installed along the conveying lines. The cleaned copra next passes through a series of size reduction equipment – primary grinders, secondary grinders and flakers, where the size is reduced to about 1/8”. The material is then, conveyed to the driers where the final moisture is adjusted to 2%-3%. The cooked/dried copra is fed to the expellers for extraction of the oil by means of mechanical pressing to about 15%-18% residual oil in the cake. Expeller oil, containing fine solids, is conveyed to the filtration section for purification then pumped to the storage tanks.

So far so good. However, we're not done.

Copra cake from the expellers goes to the solvent extraction plant where it undergoes continuous washing with hexane for more efficient extraction of oil from the meal. This chemically extracted oil is pumped to the filtration section for blending with the expeller oil and purification.

(Unfortunately, trace amounts of hexane remain. Is this a problem? Yes. Hexane is a petroleum based solvent that can seriously impact health. Side effects from exposure to hexane include dizziness, drowsiness, dullness, headache, nausea, weakness, unconsciousness, and abdominal pain. As a side note, hexane tends to concentrate in the meal, which is sold as animal feed. Excessive amounts of solvent in meal causes anemia in livestock. Hexane compounds are carcinogens according to the Environmental Protection Agency and are classed as a hazardous substance. Hexane also poses a serious environmental threat as it is a hydrocarbon polluter and produces ozone and air pollution when it is vented into the atmosphere during the flash off cycle. Incidentally, hexane is the solvent of choice in extracting most “natural” vitamin isolates. That means there are traces of hexane in most vitamins that you buy. But more on that in another newsletter.)

Refining Oil

Once extracted, the oil "needs" to be refined. The refining process involves the treatment of the crude oil with a lye solution to reduce the Free Fatty Acid (FFA) content to a final value of 0.05%. This is done primarily to prevent spoilage, to help your oil last an eternity on the grocer's shelf. (Note: Free fatty acids are not necessarily bad. Conjugated Linoleic Acid (found in meat and dairy products) is a naturally occurring free fatty acid that has been shown to improve nutrient usage, promote muscle tone, significantly reduce body fat, and have anti-tumor properties as well.)

In addition, other impurities in the oil such as gums, phosphatides, pigments and other oxidation products which would “impair” the taste, odor, keeping quality, and other "desired" properties of the oil are, likewise, removed. This degumming and neutralization process is accomplished by means of phosphoric acid and more lye. The now "neutral" oil is next mixed with bleaching earth (a type of clay) and activated carbon for reduction of the color. Final purification is effected by means of filters presses and polishing filters, then pumped to the storage tanks.

Deodorizing Oil

All edible oils and fats contain certain compounds which give the particular oil its identifiable taste. In all commercial oils, these compounds are removed to make the oil as neutral tasting as possible. This is process is called deodorization and because of the temperatures involved is the part of the process most damaging to the oil.

Refined bleached oil from the refining section is first transferred to a de-aerator operating under a vacuum for removal of any entrained air. The oil then passes through a series of heaters where the temperature is raised to the level desirable for efficient steam distillation and deodorization process.Temperatures used in a deodorizing steam column reach upwards of 200° C, or 450° F. At these temperatures, the fundamental structure of the oil is changed into a different form of fatty acid in a process called isomerization, a form not beneficial to the human body. As a side note, the high heat also causes a small amount of trans fatty acids to be formed.) Live steam is blown in at the bottom of the column to vaporize the odor and taste imparting components from the bulk of the oil. The fully deodorized and refined oil is withdrawn from the column passing to a cooler and polishing filter basket for removal of any fine suspension before being finally pumped to the storage tank.

The final result is an oil that is virtually colorless, odorless, and tasteless – that can last for years in a bottle with no danger of spoilage. On the other hand, it has virtually no connection with the beneficial oil that was originally contained in the seed or coconut. It is now a “plastic fat” that offers no benefits to the human body and the potential for much harm.

Choosing a Healthy Oil

The bottom line is that when possible buy and use organic, unrefined, cold-processed vegetable oils. Use olive oil in salads. Use avocado oil for cooking. Avocado oil has a very high smoke point by comparison to other cooking oils. It will not burn or smoke until it reaches 255°C, which is ideal for searing meats and frying in a Wok. Another good cooking oil is rice bran oil. Again, look for organic, cold-processed oil.

PS: And, of course, it goes without saying that anything that contains hydrogenated or partially hydrogenated oil is an absolute no-no, and should be avoided in the same way that one should avoid playing Russian Roulette..


All about oil! This post will talk about the different kinds of oils we use in our salads, stir fries, baked goods and more. There are refined oils and unrefined oils, virgin, extra-virgin, cold-pressed…etc. What does this mean in terms of how healthy they are? If you want to know more about which cooking oils are healthiest and which are best for high-heat, low-heat, then keep reading. And remember to not be afraid of some oils. Healthy fats are good for you, when they are in moderation, as with everything else!

What are the Healthiest Oils to be using in our salads and in our cooking? Not all are created equally.

There are so many different kinds of oils available to us: Canola Oil, Extra Virgin Olive Oil, Sweet Almond Oil, Rapeseed Oil, Avocado Oil, Sunflower Oil, Sesame Oil, Peanut Oil, Coconut Oil, Corn Oil, Soy Bean Oil and more. It can be a bit daunting if you are used to using the same kind for everything. Firstly, let’s talking about the two different categories of oil:

  • Refined Oils
  • Unrefined Oils

Do you know which oils fall into which category and what the differences between refined and unrefined oils? Which one is healthiest and which ones should we use for salads, stir fries, deep-frying and pancake-making? Keep reading and find out!


*UNREFINED OILS (not extensive list):

  • Extra Virgin Olive Oil
  • Avocado Oil
  • Sesame Oil
  • Macadamia Oil

Unrefined oils are usually cold-pressed, which means the oils are mechanically extracted by a machine which applies pressure and not heat. This leaves the high flavour and nutrient content in the oils, making them a healthier choice.  You may have seen “Cold Pressed Coconut Oil” at the store. This means it is an unrefined oil.

*REFINED OILS (not extensive list):

  • Canola Oil
  • Ricebran Oil
  • Soya Oil
  • Sunflower Oil

Refined oils are extracted using heat and a solvent, which are then bleached and deodorized. Doesn’t sound too healthy, does it?

The Smoking Points of Oils – Low and High Smoking Points and Why it’s important

Knowing the different smoking points of oils is important. You don’t have to memorize the temperatures, but it is important to know which are better for high temperatures and which are best for cold or low temperatures.

  • When an oil starts to smoke when it is heated, it means that it is starting to break down. This also alters the flavour. Refined oils generally have a higher smoke point and are therefore more commonly used in things like deep-frying.
  • Unrefined Oils, such as Coconut oil and Avocado oil are not good to use with high temperatures. There are a number of reasons for this. The more an oil is heated, the more it loses its flavour, and since unrefined oils have more flavour, you should use them in things like salads and cold dishes, or at least for when you are not needing to use very high temperatures. It is fine to use them in stir fries and for making pancakes and such (I love using coconut oil to make pancakes!), just don’t use them for things such as deep-frying, as the oil can even catch on fire if heated too high, which can be very dangerous.

What’s the difference between Virgin Olive Oil and Extra-Virgin Olive Oil and Pure and Light Olive Oil?

  • Whether the Olive Oil is Extra-Virgin, Virgin, Pure or Light depends on the olive’s chemical attributes and the way the oil is pressed. Extra Virgin Olive Oil and Virgin Olive Oil are cold pressed, making them unrefined and a healthier choice than Pure or Light.
  • Extra Virgin Olive oil is less acidic than Virgin olive oil. This gives it a sweeter flavour.
  • Unlike wine, Oil is best when it is fresh. Oil should be consumed within the first 1-2 years that an oil is pressed. Check the bottle of oil for the “Pressed on” date. You shouldn’t bye oils in clear containers as light will degrade the oil’s quality. Store your oils, regardless of type, in a cool, dark place.

All these facts and information on oil are found in this very informative and concise 20 minute video on oils. I suggest giving it a watch as it is more enjoyable than reading my text and it has really been informative and I learned a lot in just 20 minutes. Note: You do have to sign up, but if you don’t want to get a subscription, just cancel before 10 days are up.

Watch What’s Really in Our Food.

Conclusion: Unrefined Oils are Healthier than Refined Oils. They have stronger flavours, more nutrients and because they are not used for deep-frying, the dishes you make using unrefined oils are probably going to be healthier than if you are using refined oils. Some unrefined oils, such as Coconut Oil are often said to aid in weight loss, despite the fact that all oils are made up of 100% fat. (Remember, our body needs certain kinds of fats in our bodies, so don’t omit all healthy fats from your diet. Everything is good in moderation and you wouldn’t be doing your body any favours by eliminating them).