Vegetable Oil

Vegetable fats and oils are lipid materials derived from plants. Physically, oils are liquid at room temperature, and fats are solid. Chemically, both fats and oils are composed of triglycerides, as contrasted with waxes which lack glycerin in their structure. Although many different parts of plants may yield oil, in commercial practice, oil is extracted primarily from seeds.

The melting temperature distinction between oils and fats is imprecise, since definitions of room temperature vary, and typically natural oils have a melting range instead of a single melting point.

Vegetable fats and oils may be edible or inedible. Examples of inedible vegetable fats and oils include processed linseed oil, tung oil, and castor oil used in lubricants, paints, cosmetics, pharmaceuticals, and other industrial purposes. Although thought of as esters of glycerin and a varying blend of fatty acids, fats and oils also typically contain free fatty acids, monoglycerides, and diglycerides.

Oils extracted from plants have been used in many cultures, since ancient time. As an example, in a 4,000 year old "kitchen" unearthed in Indiana's Charlestown State Park, archaeologist Bob McCullough of IPFW found evidence that natives used large slabs of rock to crush hickory nuts, then boiled them in water to extract the oil.

Culinary uses

Many vegetable oils are consumed directly, or used directly as ingredients in food - a role that they share with some animal fats, including butter and ghee. The oils serve a number of purposes in this role:

Shortening - to give pastry a crumbly texture .

Texture - oils can serve to make other ingredients stick together less.

Flavor - while less-flavorful oils command premium prices, oils such as olive oil or almond oil may be chosen specifically for the flavor they impart.

Flavor base - oils can also "carry" flavors of other ingredients, since many flavors are present in chemicals that are soluble in oil.

Secondly, oils can be heated, and used to cook other foods. Oils that are suitable for this purpose must have a high flash point. Such oils include the major cooking oils - canola, sunflower, safflower, peanut etc. Some oils, including rice bran oil, are particularly valued in Asian cultures for high temperature cooking, because of their unusually high flash point.

Hydrogenated oils

Unsaturated vegetable fats and oils can be transformed through partial or complete hydrogenation into fats and oils of higher melting point. The hydrogenation process involves "sparging" the oil at high temperature and pressure with hydrogen in the presence of a catalyst, typically a powdered nickel compound. As each double-bond is broken, two hydrogen atoms each form single bonds with the two carbon atoms. 

The elimination of double-bonds by adding hydrogen atoms is called saturation; as the degree of saturation increases, the oil progresses towards being fully hydrogenated. An oil may be hydrogenated to increase resistance to rancidity (oxidation) or to change its physical characteristics. As the degree of saturation increases, the oil's viscosity and melting point increase.

The use of hydrogenated oils in foods has never been completely satisfactory. Because the center arm of the triglyceride is shielded somewhat by the end fatty acids, most of the hydrogenation occurs on the end fatty acids. This makes the resulting fat more brittle. 

A margarine made from naturally more saturated oils will be more plastic (more "spreadable") than a margarine made from, say, hydrogenated soy oil. In addition, partial hydrogenation results in the formation of large amounts trans fats in the oil mixture, which, since the 1970s, have increasingly been viewed as unhealthy.

History in North America

While olive oil and other pressed oils have been around for millennia, Procter & Gamble researchers were innovators when they started selling cottonseed oil as a creamed shortening, in 1911. Ginning mills were happy to have someone haul away the cotton seeds. Procter & Gamble researchers learned how to extract the oil, refine it, partially hydrogenate it (causing it to be solid at room temperature and thus mimic natural lard), and can it under nitrogen gas. 

Compared to the rendered lard Procter & Gamble was already selling to consumers, Crisco was cheaper, easier to stir into a recipe, and could be stored at room temperature for two years without turning rancid. (Procter & Gamble sold their fats and oils brands - Jif and Crisco - to The J.M. Smucker Co. in 2002.)

Soybeans were an exciting new crop from China in the 1930s. Soy was protein-rich, and the light tasteless oil was extremely high in polyunsaturates. 

Henry Ford established a soybean research laboratory, developed soybean plastics and a soy-based synthetic wool, and built a car almost entirely out of soybeans. Roger Drackett had a successful new product with Windex, but he invested heavily in soybean research, seeing it as a smart investment. By the 1950s and 1960s, soybean oil had become the most popular vegetable oil in the US.

In the mid-1970s, Canadian researchers developed a low-erucic rapeseed cultivar. Because the word "rape" was not considered optimal for marketing, they coined the name "canola" (from "Canada Oil"). 

The FDA approved use of the canola name in January 1985, and U.S. farmers started planting large areas that spring. Canola oil is lower in saturated fats, and higher in mono-unsaturates and is a better source of omega-3 fats than other popular oils. 

Canola is very thin (unlike corn oil) and flavorless (unlike olive oil) so it largely succeeds by displacing soy oil, just as soy oil largely succeeded by displacing cottonseed oil.

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