Vegetable oils are triglycerides extracted from plants. Some of these oils have been part of human culture for millennia. Edible vegetable oils are used in food, both in cooking and as supplements. Many oils, edible and otherwise, are burned as fuel, such as in oil lamps and as a substitute for petroleum-based fuels. Some of the many other uses include wood finishing, oil painting, and skin care.

Definition

The term "vegetable oil" can be narrowly defined as referring only to substances that are liquid at room temperature, or broadly defined without regard to a substance's state (liquid or solid) at a given temperature. While a large majority of the entries in this list fit the narrower of these definitions, some do not qualify as vegetable oils according to all understandings of the term.

Classification

Vegetable oils can be classified in several ways. For instance, by their use or by the method used to extract them. In this article, vegetable oils are grouped in common classes of use.

Extraction method

There are several types of plant oils, distinguished by the method used to extract the oil from the plant. The relevant part of the plant may be placed under pressure to extract the oil, giving an expressed (or pressed) oil. The oils included in this list are of this type. Oils may also be extracted from plants by dissolving parts of plants in water or another solvent. The solution may be separated from the plant material and concentrated, giving an extracted or leached oil. The mixture may also be separated by distilling the oil away from the plant material. Oils extracted by this latter method are called essential oils. Essential oils often have different properties and uses than pressed or leached vegetable oils. Finally, macerated oils are made by infusing parts of plants in a base oil, a process called liquid–liquid extraction.

Sources and Uses

Most, but not all vegetable oils are extracted from the fruits or seeds of plants. For instance, palm oil is extracted from palm fruits, while soybean oil is extracted from soybean seeds. Vegetable oils may also be classified by grouping oils extracted from similar plants, such as "nut oils". Although most plants contain some oil, only the oil from certain major oil crops complemented by a few dozen minor oil crops is widely used and traded.

Use

Oils from plants are used for several different purposes. Edible vegetable oils may be used for cooking, or as food additives. Many vegetable oils, edible and otherwise, are burned as fuel, for instance as a substitute for petroleum-based fuels. Some may be also used for cosmetics, medical purposes, wood finishing, oil painting and other industrial purposes.

Edible oils

Major oils

These oils make up a significant fraction of worldwide edible oil production. All are also used as fuel oils.

Nut oils

Nut oils are generally used in cooking, for their flavor. Most are quite costly, because of the difficulty of extracting the oil.

Citrus oils

A number of citrus plants yield pressed oils. Some, such as lemon and orange oil, are used as essential oils, which is uncommon for pressed oils.<ref group="note">Lime oil, for example, is distilled, not pressed. See Jackson, p. 131 The seeds of many if not most members of the citrus family yield usable oils.

Oils from melon and gourd seeds

Members of the Cucurbitaceae include gourds, melons, pumpkins, and squashes. Seeds from these plants are noted for their oil content, but little information is available on methods of extracting the oil. In most cases, the plants are grown as food, with dietary use of the oils as a byproduct of using the seeds as food.

Food supplements

A number of oils are used as food supplements (or "nutraceuticals"), for their nutrient content or purported medicinal effect. Borage seed oil, blackcurrant seed oil, and evening primrose oil all have a significant amount of gamma-Linolenic acid (GLA) (about 23%, 15–20% and 7–10%, respectively), and it is this that has drawn the interest of researchers.

Other edible oils

Oils used for biofuel

A number of oils are used for biofuel (biodiesel and Straight Vegetable Oil) in addition to having other uses. Other oils are used only as biofuel. Although diesel engines were invented, in part, with vegetable oil in mind, diesel fuel is almost exclusively petroleum-based. Vegetable oils are evaluated for use as a biofuel based on:

Multipurpose oils also used as biofuel

The oils listed immediately below are all (primarily) used for other purposes – all but tung oil are edible – but have been considered for use as biofuel.

Inedible oils used only or primarily as biofuel

These oils are extracted from plants that are cultivated solely for producing oil-based biofuel. These, plus the major oils described above, have received much more attention as fuel oils than other plant oils.

Drying oils

Drying oils are vegetable oils that dry to a hard finish at normal room temperature. Such oils are used as the basis of oil paints, and in other paint and wood finishing applications. In addition to the oils listed here, walnut, sunflower and safflower oil are also considered to be drying oils.

Other oils

A number of pressed vegetable oils are either not edible, or not used as an edible oil.