Vegetable oil

Vegetable oil or vegoil is fat extracted from plant sources, known as oil plants. Although in principle other parts of plants may yield oil, in practice seeds form the almost exclusive source. Vegetable oils are used as cooking oils and for industrial uses. Some types, such as cottonseed oil, castor oil and some types of rapeseed oil, are not fit for human consumption without further processing.

Like all fats, vegetable oils are esters of glycerin and a varying blend of fatty acids, and are insoluble in water but soluble in organic solvents.

Uses of vegetable oil

Oils extracted from plants have been used in many cultures, since ancient times. As an example, a 4,000 year old "kitchen" unearthed in southestern Indiana was found to include an oil press and a large quantity of discarded hickory nut shells. Archeologists believe that the tribes would store the high-energy nut oils as a winter food supply.^*

The uses of vegetable oils can be divided into four main areas:

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:

Texture - oils can serve to make other ingredients stick together less.
Flavor - many nut oils are used in foods because of their intense flavor.
Flavor base - oils can also "carry" the 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 oil, safflower oil, peanut oil, etc. Some oils, including rice bran oil, are particularly valued in Asian cultures for high temperature cooking, because of their unusually high flash point.

Medical uses

Medical use of vegetable oils has a long and distinguished history. Many oils that are use medicinally are essential oils, which are distilled rather than pressed or otherwise extracted. Medical properties claimed by those who sell medicinal oils vary from skin treatments to remedies for cancer, and are often based on historical use of these oils for these purposes. Such claims are now subject to regulation in most countries, and have grown correspondingly more vague, to stay within these regulations.

Interest in such uses of essential oils has enjoyed a revival in recent decades, with the popularity of aromatherapy, in which oils are heated and volatilized.

Industrial uses

Many vegetable oils are used to make soaps, skin products, perfumes and other personal care and cosmetic products.

Some oils are particularly suitable as drying agents, and are used in making paints and other wood treatment products. Dammar oil, for example, is used almost exclusively in treating the hulls of wooden boats.

Vegetable oils are increasingly being used in the electrical industry as insulators as vegetable oils are non-toxic to the environment, biodegradable if spilled and have high flash and fire points. However, vegetable oils have issues with chemical stability (there has to be a tradeoff with biodegradability), so they are generally used in systems where they are not exposed to oxygen and are more expensive than crude oil distillate. Three examples are Midel 7131 by M & I materials, FR3 by Cooper Power and Biotemp by ABB. Midel 7131 is a synthetic oil, manufactured by an alcohol + acid reaction.

Common vegetable oil has also been used experimentally as a cooling agent in PCs.

One limiting factor in industrial uses of vegetable oils is that all such oils eventually decompose, chemically, turning rancid. Oils that are more stable (e.g. Ben oil) are therefore particularly valued for industrial application.

Fuel

Vegetable oils are also the basis of biodiesel, which can be used like conventional diesel, and SVO (straight vegetable oil), which can be used in specially prepared vehicle engines.

Types of vegetable oil

The following vegetable oils account for almost all world-wide production, by volume. All are used as both cooking oils and as SVO or to make biodiesel.

Corn oil, one of the most common, and inexpensive cooking oils.
Cottonseed oil, a major food oil, often used in industrial food processing.
Canola oil/Rapeseed oil, one of the most widely used cooking oils, from a (trademarked) cultivar of rapeseed.
Olive oil, used in cooking, cosmetics, soaps and as a fuel for traditional oil lamps
Palm oil, the most widely produced tropical oil. Also used to make biofuel.
Peanut oil/Ground nut oil, mild-flavored cooking oil.
Safflower oil, a flavorless and colorless cooking oil.
Sesame oil, used as a cooking oil, and as a massage oil, particularly in India.
Soybean oil, accounts for about half of worldwide edible oil production.
Sunflower oil, a common cooking oil, also used to make biodiesel.

A selection of other oils includes:

Algae oil
Almond oil, from the almond nut
Apricot oil, from the seeds of the apricot
Argan oil, from the argan plant
Avocado oil, from the seeds of the avocado
Ben oil, from the seeds of the moringa oleifera
Cashew oil, from cashew nuts
Castor oil, from castor beans
Grape seed oil
Hazelnut oil
Hemp seed oil, from the cannabis plant
Linseed oil, from flax seeds
Mustard oil, from the mustard plant
Neem oil, from the neem tree
Palm kernel oil - from the seed of the African palm tree
Pumpkin seed oil
Rice bran oil, from rice grains
Walnut oil

Consumption

According to the USDA, the total world consumption of major vegetable oils in 2000 was:

Oil source	World consumption (megatonnes)
Soybeans	26.0
Palm	23.3
Rapeseed	13.1
Sunflowerseed	8.6
Peanut	4.2
Cottonseed	3.6
Palm Kernel	2.7
Olive	2.5

Note that these figures include industrial and animal feed use. The majority of European rapeseed oil production is used to produce biodiesel, or used directly as fuel in diesel cars which may require modification to heat the oil to reduce its higher viscosity. The suitability of the fuel should come as little surprise, as Rudolph Diesel originally designed his engine to run on peanut oil.

Extraction

The "modern" way of processing vegetable oil is by chemical extraction, using solvent extracts, which produces higher yields and is quicker and less expensive. The most common solvent is petroleum-derived hexane. This technique is used for most of the "newer" industrial oils such as soybean and corn oils.

Another way is "physical extraction," which does not use solvent extracts. It is made the "traditional" way using several different types of mechanical extraction. This method is typically used to produce the more traditional oils (e.g., olive), and it is preferred by most "health-food" customers in the USA and in Europe. Expeller-pressed extraction is one type, and there are two other types that are both oil presses: the screw press and the ram press. Oil seed presses are commonly used in developing countries, among people for whom other extraction methods would be prohibitively expensive. ^*

Supercritical carbon dioxide can also be used for the extraction purpose and it is non toxic.^*

Production

Crude oil, straight from the crushing operation, is not considered edible in the case of most oilseeds. The same is true for the remaining meal. For instance, animals fed raw soy meal will waste away, even though soy meal is high in protein. Researchers at Central Soya discovered that a trypsin inhibitor in soybeans could be deactivated by toasting the meal, and both licensed their invention, and sold soy meal augmented with vitamins and minerals as MasterMix, a product for farmers to mix with their own grain to produce a high quality feed.

The processing of soy oil is typical of that used with most vegetable oils. Crude soy oil is first mixed with caustic soda. Saponification turns free fatty acids into soap. The soap is removed with a centrifuge. Neutralized dry soap stock (NDSS) is typically used in animal feed, more to get rid of it than because it is particularly nourishing. The remaining oil is deodorized by heating under a near-perfect vacuum and sparged with water. The condensate is further processed to become vitamin E food supplement, while the oil can be sold to manufacturers and consumers at this point.

Some of the oil is further processed. By carefully filtering the oil at near-freezing temperatures, "winter oil" is produced. This oil is sold to manufacturers of salad dressings, so that the dressings do not turn cloudy when refrigerated.

The oil may be partially hydrogenated to produce various ingredient oils. Lightly hydrogenated oils have very similar physical characteristics to regular soy oil, but are more resistant to becoming rancid.

Margarine oils need to be mostly solid at 32 °C (90 °F) so that the margarine does not melt in warm rooms, yet it needs to be completely liquid at 37 °C (98 °F), so that it doesn't leave a "lardy" taste in the mouth.

Another major use of soy oil is for fry oils. These oils require substantial hydrogenation to keep the polyunsaturates of soy oil from becoming rancid.

Hardening vegetable oil is done by raising a blend of vegetable oil and a catalyst in near-vacuum to very high temperatures, and introducing hydrogen. This causes the carbon atoms of the oil to break double-bonds with other carbons, each carbon forming a new single-bond with a hydrogen atom. Adding these hydrogen atoms to the oil makes it more solid, raises the smoke point, and makes the oil more stable.

Hydrogenated vegetable oils differ in two major ways from other oils which are equally saturated. During hydrogenation, it is easier for hydrogen to come into contact with the fatty acids on the end of the triglyceride, and less easy for them to come into contact with the center fatty acid. This makes the resulting fat more brittle than a tropical oil; soy margarines are less "spreadable". The other difference is that trans fatty acids (often called trans fat) are formed in the hydrogenation reactor, and may amount to as much as 40 percent by weight of a partially hydrogenated oil. Trans acids are increasingly thought to be unhealthy.

History of vegetable oils in the United States

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. P&G 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 P&G 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. (P&G 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 became the most popular vegetable oil in the US.

In the mid-1970s, Canadian researchers developed a low-ecruic 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 acreages 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.

Waste Vegetable Oil

As of 2000, the United States were producing in excess of 11 billion liters of waste vegetable oil annually, mainly from industrial deep fryers in potato processing plants, snack food factories and fast food restaurants.

Waste vegetable oil, sold as the commodity yellow grease has a market value of approximately ^*]1.09" target="_blank" >per US gallon ($0.29/l or $335 per metric tonne), expected to rise to $1.21 by 2013, enough to make collection economically viable.[http://tonto.eia.doe.gov/FTPROOT/environment/biodiesel.pdf

Currently, the largest uses of waste vegetable oil in the U.S. are for animal feed, pet food, and cosmetics. Since 2002, an increasing number of European Union countries have prohibited the inclusion of waste vegetable oil from catering in animal feed. Waste cooking oils from food manufacturing, however, as well as fresh or unused cooking oil, continues to be used in animal feed. ^*

External links

Edible Oils on hyfoma
Oil yields and characteristics.
References for use as a fuel
Oilseeds Factsheet
Oilseed Processing for Small-Scale Producers
4,000-year-old 'kitchen' unearthed in Indiana, from Archeo News, 20 January, 2006.

Other References

Beare-Rogers, J.L. 1983. "Trans and positional isomers of common fatty acids." In H.H. Draper (ed.) Advances in Nutritional Research. Vol. 5 Plenum Press, New York, pp. 171-200.
Berry, E.M. and Hirsch, J. 1986. "Does dietary linolenic acid influence blood pressure?" American Journal of Clinical Nutrition. 44: 336-340.
Beyers, E.C. and Emken, E.A. 1991. "Metabolites of cis, trans, and trans, cis isomers of linoleic acid in mice and incorporation into tissue lipids." Biochimica et Biophysica Acta. 1082: 275-284.
Birch, D.G., Birch, E.E., Hoffman, D.R., and Uauy, R.D. 1992. "Retinal development in very-low-birth-weight infants fed diets differing in omega-3 fatty acids." Investigative Ophthalmology and Visual Science 33(8): 2365-2376.
Birch, E.E., Birch, D.G., Hoffman, D.R., and Uauy, R. 1992. "Dietary essential fatty acid supply and visual acuity development." Investigative Ophthalmology and Visual Science. 33(11): 3242-3253.
Brenner, R.R. 1989. Factors influencing fatty acid chain elongation and desaturation, in the role of fats in human nutrition. 2nd edn. (eds A.J. Vergroesen and M. Crawford), Academic Press, London pp. 45-79.
British Nutrition Foundation. 1987. Report of the task force on trans fatty acids. London: British Nutrition Foundation.
Central Soya annual report, 1979.
Emken, E. A. 1984. "Nutrition and biochemistry of trans and positional fatty acid isomers in hydrogenated oils." Annual Reviews of Nutrition. 4: 339-376.
Enig, M.G., Atal, S., Keeney, M and Sampugna, J. 1990. "Isomeric trans fatty acids in the U.S. diet." Journal of the American College of Nutrition. 9: 471-486.
Ascherio, A., Hennekens, C.H., Baring, J.E., Master, C., Stampfer, M.J. and Willett, W.C. 1994. "Trans fatty acids intake and risk of myocardial infarction." Circulation. 89: 94-101.
Gurr, M.I. 1983. "Trans fatty acids: Metabolic and nutritional significance." Bulletin of the International Dairy Federation. Document 166: 5-18.
Hui Y. H., editor, "Bailey's Industrial Oil and Fat Products," Edible Oil and Fat Products
Koletzko, B. 1992. "Trans fatty acids may impair biosynthesis of long-chain polyunsaturates and growth in man." Acta Paediatrica. 81: 302-306.
Lief, Alfred, It floats: The story of Procter & Gamble, published 1958 by Rinehart.
MacMillen, Harold W., Mr. Mac and Central Soya: the foodpower story, published 1967 by Newcomen Society
Marchand, C.M. 1982. "Positional isomers of trans-octadecenoic acids in margarine." Canadian Institute of Food Science and Technology Journal. 15: 196-199.
Mensink, R.P., Zock, P.L., Katan, M.B. and Hornstra, G. 1992. "Effect of dietary cis-and trans-fatty acids on serum lipoprotein^* levels in humans." Journal of Lipid Research. 33: 1493-1501.
Siguel, E.N. and Lerman, R.H. 1993. "Trans fatty acid patterns in patients with angiographically documented coronary artery disease." American Journal of Cardiology. 71: 916-920.
Troisi, R., Willett, W.C. and Weiss, S.T. 1992. "Trans-fatty acid intake in relation to serum lipid concentrations in adult men." American Journal of Clinical Nutrition. 56: 1019-1024.
Willett, W.C., Stampfer, M.J., Manson, J.E., Colditz, G.A., Speizer, F.E., Rosner, B.A., Sampson, L.A. and Hennekens, C.H. 1993. "Intake of trans fatty acids and risk of coronary heart disease among women." The Lancet. 341: 581-585.

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