Plant oils or vegetable oils are

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

s derived from plant sources, as opposed to

animal fat Animal fats and oils are lipids derived from animals: oils are liquid at room temperature, and fats are solid. Chemically, both fats and oils are composed of triglycerides. Although many animal parts and secretions may yield oil, in commercial p ...

s or

petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

. There are three primary types of plant oil, differing both the means of extracting the relevant parts of the plant, and in the nature of the resulting oil: #

Vegetable fats and oils Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fat ...

were historically extracted by putting part of the plant under

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

, squeezing out the oil. # Macerated oils consist of a base oil to which parts of plants are added. #

Essential oil An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the o ...

s are composed of volatile aromatic compounds, extracted from plants by

distillation Distillation, or classical distillation, is the process of separation process, separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distilla ...

Vegetable fats and oils

are what are most commonly called vegetable oils. These are

triglyceride A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride''). Triglycerides are the main constituents of body fat in humans and other vertebrates, as w ...

-based, and include cooking oils like

canola oil Close-up of canola blooms Canola flower Rapeseed oil is one of the oldest known vegetable oils. There are both edible and industrial forms produced from rapeseed, the seed of several cultivars of the plant family Brassicaceae. Historically, i ...

, solid oils like

cocoa butter Cocoa butter, also called theobroma oil, is a pale-yellow, edible fat extracted from the cocoa bean. It is used to make chocolate, as well as some ointments, toiletries, and pharmaceuticals. Cocoa butter has a cocoa flavor and aroma. Its melti ...

, oils used in

paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...

linseed oil Linseed oil, also known as flaxseed oil or flax oil (in its edible form), is a colourless to yellowish oil obtained from the dried, ripened seeds of the flax plant (''Linum usitatissimum''). The oil is obtained by pressing, sometimes followed by ...

and oils used for industrial purposes. Pressed vegetable oils are extracted from the plant containing the oil (usually the seed), using one of two types of oil press. The most common is the ''screw press'', which consists of a large-diameter metal screw inside a metal housing. Oil seeds are fed into the housing, where the screws mash the seeds, and create pressure which forces the oil out through small holes in the side of the press. The remaining solids, called ''seed cake'', are either discarded or used for other purposes. Oil presses can be either manual or powered. The second type of oil press is the ''ram press'', where a piston is driven into a cylinder, crushing the seeds and forcing out the oil. Ram presses are generally more efficient than screw presses. There has been recent interest in improving the design of mechanical oil presses, particularly for use in developing countries. A press developed at

MIT The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the m ...

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D-Lab
for example, is capable of exerting 800–1,000psi to extract peanut oil. Industrial machines for extracting oil mechanically are call ''expellers''. Many expellers add heat and pressure, in order to increase the amount of oil extracted. If the temperature does not exceed 120 °F, the oil can be called "cold-pressed". In modern vegetable oil production, oils are usually extracted chemically, using a

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

such as

hexane Hexane () is an organic compound, a straight-chain alkane with six carbon atoms and has the molecular formula C6H14. It is a colorless liquid, odorless when pure, and with boiling points approximately . It is widely used as a cheap, relatively ...

. Chemical extraction is cheaper and more efficient than mechanical extraction, at a large scale, leaving only 0.5–0.7% of the oil in the plant solids, as compared to 6–14% for mechanical extraction.

Macerated oils

Macerated or infused oils are oils to which other matter has been added, such as herbs or flowers. Typically, the oil used is a food-grade fat-type oil.

Essential oils

s are not oils but volatile aromatic compounds that are used in flavors, fragrances, and in

aroma therapy Aromatherapy is based on the usage of aromatic materials including essential oils and other aroma compounds, with claims for improving psychological and physical well-being. It is offered as a complementary therapy or as a form of alternative me ...

for health purposes. Essential oils are usually extracted by

. Maceration is also used as a means of extracting essential oils. In this process, used, for example, to extract the onion, garlic, wintergreen and bitter almond essential oil, the plant material is macerated in warm water to release the volatile compounds in the plant.

References

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Vegetable fats and oils

Macerated oils

Essential oils

References

See also