Cooking oil

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Cooking oil is plant, animal, or synthetic fat used in frying, baking, and other types of cooking. It is also used in food preparation and flavouring not involving heat, such as salad dressings and bread dips, and in this sense might be more accurately termed edible oil.

Cooking oil is typically a liquid at room temperature, although some oils that contain saturated fat, such as coconut oil, palm oil and palm kernel oil are solid.[1]

There is a wide variety of cooking oils from plant sources such as olive oil, palm oil, soybean oil, canola oil (rapeseed oil), corn oil, peanut oil and other vegetable oils, as well as animal-based oils like butter and lard.

Oil can be flavoured with aromatic foodstuffs such as herbs, chillies or garlic.

Health and nutrition[edit]

Olive oil

The appropriate amount of fat as a component of daily food consumption is established as a guideline by regulatory agencies such as the FDA which recommends that 10% or fewer of calories consumed daily should be from saturated fat and 20-35% of total daily calories come from polyunsaturated and monounsaturated fats.[2]

While consumption of small amounts of saturated fats is common in diets,[3] meta-analyses found a significant correlation between high consumption of saturated fats and blood LDL concentration,[4] a risk factor for cardiovascular diseases.[5] Other meta-analyses based on cohort studies and on controlled, randomized trials found a positive[6] or neutral[7] effect from shifting consumption from saturated fats to polyunsaturated fats (10% lower risk for 5% replacement).[7]

Mayo Clinic has highlighted oils that are high in saturated fats, including coconut, palm oil and palm kernel oil. Those having lower amounts of saturated fats and higher levels of unsaturated (preferably monounsaturated) fats like olive oil, peanut oil, canola oil, soy and cottonseed oils are generally healthier.[8] The US National Heart, Lung and Blood Institute[9] urged saturated fats be replaced with polyunsaturated and monounsaturated fats, listing olive and canola oils as sources of healthier monounsaturated oils while soybean and sunflower oils as good sources of polyunsaturated fats. One study showed that consumption of non-hydrogenated unsaturated oils like soybean and sunflower are preferable to the consumption of palm oil for lowering the risk of heart disease.[10]

Peanut, cashew and other nut-based oils may present a hazard to persons with a nut allergy.

Trans fats[edit]

Unlike other dietary fats, trans fats are not essential, and they do not promote good health.[11] The consumption of trans fats increases one's risk of coronary heart disease[12] by raising levels of "bad" LDL cholesterol and lowering levels of "good" HDL cholesterol.[13] Trans fats from partially hydrogenated oils are more harmful than naturally occurring oils.[14]

Several large studies[15][16][17][18] indicate a link between consumption of high amounts of trans fat and coronary heart disease and possibly some other diseases. The United States Food and Drug Administration (FDA), the National Heart, Lung and Blood Institute and the American Heart Association (AHA) all have recommended limiting the intake of trans fats.

Cooking with oil[edit]

Heating an oil changes its characteristics. Oils that are healthy at room temperature can become unhealthy when heated above certain temperatures. When choosing a cooking oil, it is important to match the oil's heat tolerance with the cooking method.[19]

Palm oil contains more saturated fats than canola oil, corn oil, linseed oil, soybean oil, safflower oil, and sunflower oil. Therefore, palm oil can withstand the high heat of deep frying and is resistant to oxidation compared to highly unsaturated vegetable oils.[20] Since about 1900, palm oil has been increasingly incorporated into food by the global commercial food industry because it remains stable in deep frying or in baking at very high temperatures[21][22] and for its high levels of natural antioxidants.[23]

Oils that are suitable for high-temperature frying (above 230 °C or 446 °F) because of their high smoke point:

Storing and keeping oil[edit]

Whether refined or not, all oils are sensitive to heat, light, and exposure to oxygen. Rancid oil has an unpleasant aroma and acrid taste, and its nutrient value is greatly diminished.[citation needed] To delay the development of rancid oil, a blanket of an inert gas, usually nitrogen, is applied to the vapor space in the storage container immediately after production. This is referred to as tank blanketing. Vitamin E oil is a natural antioxidant that can also be added to cooking oils to prevent rancidification.

All oils should be kept in a cool, dry place. Oils may thicken, but they will soon return to liquid if they stand at room temperature. To prevent negative effects of heat and light, oils should be removed from cold storage just long enough for use. Refined oils high in monounsaturated fats keep up to a year (olive oil will keep up to a few years), while those high in polyunsaturated fats keep about six months. Extra-virgin and virgin olive oils keep at least 9 months after opening. Other monounsaturated oils keep well up to eight months, while unrefined polyunsaturated oils will keep only about half as long.[citation needed]

In contrast, saturated oils, such as coconut oil and palm oil, have much longer shelf lives and can be safely stored at room temperature.[citation needed] Their lack of polyunsaturated content causes them to be more stable.[25]

Types of oils and their characteristics[edit]

Lighter, more refined oils tend to have a higher smoke point. Experience using an oil is generally a sufficiently reliable guide. Although outcomes of empirical tests are sensitive to the qualities of particular samples (brand, composition, refinement, process), the data below should be helpful in comparing the properties of different oils.[citation needed]

Smoking oil indicates a risk of combustion, and left unchecked can also set off a fire alarm. When using any cooking oil, should it begin to smoke, reduce the heat immediately. The cook should be fully prepared to extinguish a burning oil fire before beginning to heat the oil, by having on hand the lid to place on the pan, or (for the worst case) having on hand the proper fire extinguisher.

Type of oil or fat Saturated Monounsaturated Polyunsaturated Omega-3 Omega-6 Smoke point
[note 1]
Almond 8% 66% 26% 0 17% 221 °C (430 °F) Baking, sauces, flavoring
Avocado oil 12% 74% 14% 0.95% 12% 271 °C (520 °F) Frying, sautéing, dipping oil, salad oil
Butter 66% 30% 4% 0.3% 2.7% 150 °C (302 °F) Cooking, baking, condiment, sauces, flavoring
Ghee, clarified butter 65% 32% 3% - - 190–250 °C (374–482 °F) Deep frying, cooking, sautéing, condiment, flavoring
Canola oil 6% 62% 32% 9.1% 18% 204 °C (399 °F) Frying, baking, salad dressings
Coconut oil, (virgin) 92% 6% 2% 0 1.8% 177 °C (351 °F) Cooking, tropical cuisine, beauty products
Rice bran oil 20% 47% 33% 1.6% 33% 254 °C (489 °F) Cooking, frying, deep frying, salads, dressings. Very clean flavoured & palatable.
Corn oil 13% 25% 62% 1.1% 53% 236 °C (457 °F) Frying, baking, salad dressings, margarine, shortening
Cottonseed oil 24% 26% 50% 0.2% 50% 216 °C (421 °F) Margarine, shortening, salad dressings, commercially fried products
Flaxseed oil (Linseed oil)[28] 11% 21% 68% 53% 13% 107 °C (225 °F)[29] Salad dressings, nutritional supplement
Grapeseed oil 12% 17% 71% 0.1% 69% 204 °C (399 °F) Cooking, salad dressings, margarine
Hemp oil 9% 12% 79% 18% 55% 165 °C (329 °F) Cooking, salad dressings
Lard 41% 47% 2% 1% 10% 138–201 °C (280–394 °F) Baking, frying
Margarine, hard 80% 14% 6% 2% 22% 150 °C (302 °F)[note 2] Cooking, baking, condiment
Mustard oil 13% 60% 21% 5.9% 15% 254 °C (489 °F) Cooking, frying, deep frying, salads, dressings. Very clean flavoured & palatable.
Margarine, soft 20% 47% 33% 2.4% 23% 150–160 °C (302–320 °F) Cooking, baking, condiment
Macadamia oil 12.5% 84% 3.5% 0 2.8% 210 °C (410 °F) Cooking, frying, deep frying, salads, dressings. A slightly nutty odour.
Diacylglycerol (DAG) oil 3.05% 37.95% 59% - - 215 °C (419 °F) Frying, baking, salad oil
Olive oil (extra virgin) 14% 73% 11% 0.7% 9.8% 190 °C (374 °F) Cooking, salad oils, margarine
Olive oil (virgin) 14% 73% 11% 0.7% 9.8% 215 °C (419 °F) Cooking, salad oils, margarine
Olive oil (refined) 14% 73% 11% - - 225 °C (437 °F) Sautee, stir frying, deep frying, cooking, salad oils, margarine
Olive oil (extra light) 14% 73% 11% - - 242 °C (468 °F) Sautee, stir frying, frying, deep frying, cooking, salad oils, margarine
Palm oil 52% 38% 10% 0.2% 9.1% 230 °C (446 °F) Cooking, flavoring, vegetable oil, shortening
Peanut oil / groundnut oil 18% 49% 33% 0 31% 231 °C (448 °F) Frying, cooking, salad oils, margarine
Pumpkin seed oil 8% 36% 57% 0% 64% 121 °C (250 °F) salad oils
Safflower oil 10% 13% 77% 0 74% 265 °C (509 °F) Cooking, salad dressings, margarine
Sesame oil (Unrefined) 14% 43% 43% 0.3 41% 177 °C (351 °F) Cooking
Sesame oil (semi-refined) 14% 43% 43% 0.3 41% 232 °C (450 °F) Cooking, deep frying
Soybean oil 15% 24% 61% 6.7% 50% 241 °C (466 °F) Cooking, salad dressings, vegetable oil, margarine, shortening
Sunflower oil (linoleic, refined) 11% 20% 69% 0% 56% 246 °C (475 °F) Cooking, salad dressings, margarine, shortening
Sunflower oil (high oleic, refined)[30] 9% 82% 9% 0.2% 3.6% 225 °C (437 °F) Cooking
Tea seed oil[31] 22% 60% 18% 0.7% 22% 252 °C (486 °F) Cooking, salad dressings, stir frying, frying, margarine
Walnut oil (Semi-refined) 9% 23% 63% 10% 53% 204 °C (399 °F)[32] Salad dressings, added to cold dishes to enhance flavor

Comparison to other types of food[edit]

Cooking oil extraction and refinement[edit]

Olive oil production in Croatia

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.[38]


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 oil but not in water, 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.[38] 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 in Austin, 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.[39]

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.[40] Placing the container of oil in the refrigerator to harden also makes disposal easier and less messy.


Cooking oil can be recycled. It can be used as animal feed, directly as fuel, and to produce biodiesel,[41] 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.[42]

Yellow grease is used to feed livestock, and to make soap, make-up, clothes, rubber, detergents, and biodiesel fuel.[43][44]

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.[42] Brown grease is contaminated with rotted food solids and considered unsuitable for re-use in most applications.

Gutter oil or Trench Oil are terms used in Asia for recycled oil which is processed to resemble virgin oil but contains toxic contaminents and is illegally sold for cooking; its origin is frequently brown grease from garbage.[45]


  1. ^ 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. ^ 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]


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Further reading[edit]

External links[edit]