Cooking oil | Wikipedia audio article


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.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==A guideline for the appropriate amount of
fat—a component of daily food consumption—is established by government agencies. While consumption of small amounts of saturated
fats is common in diets, meta-analyses found a significant correlation between high consumption
of saturated fats and blood LDL concentration, a risk factor for cardiovascular diseases. Other meta-analyses based on cohort studies
and on controlled, randomized trials found a positive, or neutral, effect from consuming
polyunsaturated fats instead of saturated fats (a 10% lower risk for 5% replacement).Mayo
Clinic has highlighted certain 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. The US National Heart, Lung and Blood Institute
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 is preferable to the consumption of palm oil
for lowering the risk of heart disease.Peanut oil, cashew oil and other nut-based oils may
present a hazard to persons with a nut allergy.===Trans fats===Unlike other dietary fats, trans fats are
not essential, and they do not promote good health. The consumption of trans fats increases one’s
risk of coronary heart disease by raising levels of “bad” LDL cholesterol and lowering
levels of “good” HDL cholesterol. Trans fats from partially hydrogenated oils
are more harmful than naturally occurring oils.Several large studies indicate a link
between the 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. In the US, trans fats are no longer “generally
recognized as safe,” and cannot be added to foods, including cooking oils, without special
permission.===Cooking with oil===
Heating oil changes its characteristics. Oils that are healthy at room temperature
can become unhealthy when heated above certain temperatures, so when choosing a cooking oil,
it is important to match the oil’s heat tolerance with the temperature which will be used. Deep-fat frying temperatures are commonly
in the range of 170–190 °C (338–374 °F), less commonly, lower temperatures ≥ 130
°C (266 °F) are used.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 deep frying
at higher temperatures and is resistant to oxidation compared to high-polyunsaturated
vegetable oils. 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, and for its high levels of natural antioxidants,
though the refined palm oil used in industrial food has lost most of its carotenoid content
(and its orange-red color).The following oils are suitable for high-temperature frying due
to their high smoke point above 230 °C (446 °F): Avocado oil
Mustard oil Palm oil
Peanut oil (marketed as “groundnut oil” in the UK and India)
Rice bran oil Safflower oil
Semi-refined sesame oil Semi-refined sunflower oilLess aggressive
frying temperatures are frequently used. A quality frying oil has a bland flavor, at
least 200 °C (392 °F) smoke and 315 °C (599 °F) flash points, with maximums of 0.1%
free fatty acids and 3% linolenic acid. Those oils with higher linolenic fractions
are avoided due to polymerization or gumming marked by increases in viscosity with age. Olive oil resists thermal degradation and
has been used as a frying oil for thousands of years. Olive oil===
Storing and keeping oil===All oils degrade in response to heat, light,
and oxygen. To delay the onset of rancidity, a blanket
of an inert gas, usually nitrogen, is applied to the vapor space in the storage container
immediately after production – a process called tank blanketing. In a cool, dry place, oils have greater stability,
but may thicken, although they will soon return to liquid form if they are left at room temperature. To minimize the degrading effects of heat
and light, oils should be removed from cold storage just long enough for use. Refined oils high in monounsaturated fats,
such as macadamia oil, keep up to a year, while those high in polyunsaturated fats,
such as soybean oil, keep about six months. Rancidity tests have shown that the shelf
life of walnut oil is about 3 months, a period considerably shorter than the best before
date shown on labels.By contrast, oils high in saturated fats, such as avocado oil, have
relatively long shelf lives and can be safely stored at room temperature, as the low polyunsaturated
fat content facilitates stability.==Types and characteristics==
Cooking oils are composed of various fractions of fatty acids. For the purpose of frying food, oils high
in monounsaturated or saturated fats are generally popular, while oils high in polyunsaturated
fats are less desirable. High oleic acid oils include almond, macadamia,
olive, pecan, pistachio, and high-oleic cultivars of safflower and sunflower.===Smoke point===
The smoke point is marked by “a continuous wisp of smoke.” It is the temperature at which an oil starts
to burn, leading to a burnt flavor in the foods being prepared and degradation of nutrients
and phytochemicals characteristic of the oil.Above the smoke point are flash and fire points. The flash point is the temperature at which
oil vapors will ignite but aren’t produced in sufficient quantities to stay lit. The flash point generally occurs at about
275–330 °C (527–626 °F). The fire point is the temperature at which
hot oil produces sufficient vapors they will catch on fire and burn. As frying hours increase, all these temperature
points decrease. They depend more on an oil’s acidity than
fatty-acid profile.The smoke point of cooking oils varies generally in association with
how oil is refined: a higher smoke point results from removal of impurities and free fatty
acids. Residual solvent remaining from the refining
process may decrease the smoke point. It has been reported to increase with the
inclusion of antioxidants (BHA, BHT, and TBHQ). For these reasons, the published smoke points
of oils may vary. Oils are extracted from nuts, seeds, olives,
grains or legumes by extraction using industrial chemicals or by mechanical processes. Expeller pressing is a chemical-free process
that collects oils from a source using a mechanical press with minimal heat. Cold-pressed oils are extracted under a controlled
temperature setting usually below 105 °C (221 °F) intended to preserve naturally occurring
phytochemicals, such as polyphenols, plant sterols and vitamin E which collectively affect
color, flavor, aroma and nutrient value.==Cooking oil extraction and refinement==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.===Extraction===
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.===Refinement===
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. 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. You can also extract oil from various seeds
like, Coconut, peanuts, Sesame, walnuts and many more at home. For that you can use any cold press oil maker
machine.==Waste cooking oil==Proper disposal of used cooking oil is an
important waste-management concern. Oil can congeal in pipes, provoking blockages.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. Placing the container of oil in the refrigerator
to harden also makes disposal easier and less messy.===Recycling===Cooking oil can be recycled. It can be used as animal feed, directly as
fuel, and to produce biodiesel, 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.Yellow grease is used to feed livestock, and to make soap,
make-up, clothes, rubber, detergents, and biodiesel fuel.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 otherwise clog sewer lines and
interfere with septic systems and sewage treatment. The collected product is called brown grease
in the recycling industry. Brown grease is contaminated with rotted food
solids and considered unsuitable for re-use in most applications.===Adulteration===
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.In Kenya, thieves sell stolen electric
transformers to operators of roadside food stalls for reuse of the oil in deep frying,
suitable for prolonged use longer than regular cooking oil, but a threat to consumer health
due to the presence of PCBs and polycyclic aromatic hydrocarbons

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