Vegetable fats and oils

Plant oils
Olive oil from Oneglia.jpg
Olive oil
Types
Vegetable fats (list)
Macerated (list)
Uses
Drying oil - Oil paint
Cooking oil
Fuel - Biodiesel
Components
Saturated fat
Monounsaturated fat
Polyunsaturated fat
Trans fat

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,[1] 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 since natural oils are not chemically homogenous. Although thought of as esters of glycerin and a varying blend of fatty acids, fats and oils also typically contain free fatty acids, mono- and di- glycerides, and unsaponifiable lipids.

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.

Contents

Uses of triglyceride vegetable oil

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.[2]

Culinary uses

See also: Cooking oil

Many vegetable oils are consumed directly, or indirectly 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:

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. Tropical oils, like palm oil, coconut oil and 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 carbon-carbon double-bond is chemically reduced to a single bond, 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 toward 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 of trans fats in the oil mixture, which, since the 1970s, have increasingly been viewed as unhealthy.

(In the U.S., the USDA Standard of Identity for a product labeled as vegetable oil margarine specifies that only canola, safflower, sunflower, corn, soybean, or peanut oil may be used.[3] Products not labeled vegetable oil margarine do not have that restriction.)

Industrial uses

Vegetable oils are used as an ingredient or component in many manufactured products.

One limiting factor in industrial uses of vegetable oils is that all such oils eventually chemically decompose turning rancid. Oils that are more stable, such as Ben oil or mineral oil, are preferred for some industrial uses.

Vegetable-based oils, like castor oil, have been used as medicine and as lubricants for a long time. Castor oil has numerous industrial uses, primarily due to the presence of hydroxyl groups on the fatty acid chains. Castor oil, and other vegetable oils which have been chemically modified to contain hydroxyl groups, are becoming increasingly important in the production of polyurethane plastic for many applications. These modified vegetable oils are known as natural oil polyols.

Pet food additive

Vegetable oil is used in production of some pet foods. AAFCO defines vegetable oil, in this context, as the product of vegetable origin obtained by extracting the oil from seeds or fruits which are processed for edible purposes. In some poorer grade pet foods, the oil is listed only as "vegetable oil", without specifying the particular oil.[6]

Fuel

Vegetable oils are also used to make biodiesel, which can be used like conventional diesel. Some vegetable oil blends are used in unmodified vehicles but straight vegetable oil, also known as pure plant oil, needs specially prepared vehicles which have a method of heating the oil to reduce its viscosity. The vegetable oil economy is growing and the availability of biodiesel around the world is increasing.

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.[7] 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.[8] The amount of oil extracted using these methods varies widely, as shown in the following table for extracting mowrah butter in India:[9]

Method Percentage extracted
Ghani[10] 20-30%
Expellers 34-37%
Solvent 40-43%

Supercritical carbon dioxide can also be used for the extraction purpose and is non toxic.[11]

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 triglycerides 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.

Sparging

In the processing of edible oils, the oil is heated under vacuum to near the smoke point, and water is introduced at the bottom of the oil. The water immediately is converted to steam, which bubbles through the oil, carrying with it any chemicals which are water-soluble. The steam sparging removes impurities that can impart unwanted flavors and odors to the oil.

Particular oils

For a more comprehensive list, see List of vegetable oils

The following triglyceride vegetable oils account for almost all worldwide production, by volume. All are used as both cooking oils and as SVO or to make biodiesel. According to the USDA, the total world consumption of major vegetable oils in 2007/08 was:[12]

Oil source World consumption
(million tons)		 Notes
Palm 41.31 The most widely produced tropical oil. Also used to make biofuel.
Soybean 37.54 Accounts for about half of worldwide edible oil production.
Rapeseed 18.24 One of the most widely used cooking oils, Canola is a (trademarked) variety (cultivar) of rapeseed.
Sunflower seed 9.91 A common cooking oil, also used to make biodiesel.
Peanut 4.82 Mild-flavored cooking oil.
Cottonseed 4.99 A major food oil, often used in industrial food processing.
Palm kernel 4.85 From the seed of the African palm tree
Coconut 3.48 Used in soaps and cooking
Olive 2.84 Used in cooking, cosmetics, soaps and as a fuel for traditional oil lamps

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 Rudolf Diesel originally designed his engine to run on peanut oil.

Other significant triglyceride oils include:

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.[13] Roger Drackett had a successful new product with Windex, but he invested heavily in soybean research, seeing it as a smart investment.[14] 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,[15] 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.

Waste oil

A large quantity of waste vegetable oil is produced, mainly from industrial deep fryers in potato processing plants, snack food factories and fast food restaurants.

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.[16]

More recently, waste oil has become known for its ability to be refined into Bio Diesel fuel.

Negative health effects

A high consumption of omega-6 polyunsaturated fatty acids (PUFAs), which are found in most types of vegetable oil (e.g. soybean oil, corn oil - the most consumed in USA, sunflower oil, etc.), may increase the likelihood that postmenopausal women will develop breast cancer.[17] Similar effect was observed on prostate cancer in mice.[18] Plant based oils high in Monounsaturated Fatty Acids, such Olive oil, peanut oil, and canola oil are relatively low in omega-6 PUFAs and can be used in place of high-polyunsaturated oils. However, palm oil and coconut oil, even as unhydrogenated "natural" oils, are high in saturated fatty acids (lauric and myristic acid) that have demonstrated negative effects upon plasma cholesterol and cardiovascular risk factors.[19][20][21][22][23] In fact, they are commonly used in animal studies to induce atherosclerosis to investigate the possible causes of the disease[24][25][26][27][28]

Product labeling

There is increasing concern that the product labeling that includes "vegetable fat" or "vegetable oil" in its list of ingredients masks the identity of the fats or oils present. This has been made more pressing as concerns have been raised over the environmental impact of palm oil in particular, especially given the predominance of palm oil.[29]

See also

Notes and references

  1. ↑ Compare, for examp-[-[le, the list of raw materials from which essential oils are extracted.
  2. ↑ "4,000-year-old 'kitchen' unearthed in Indiana". http://www.stonepages.com/news/archives/001708.html. Retrieved 2006-07-31. 
  3. ↑ "USDA Standard of Identity". http://www.ams.usda.gov/dairy/vegoil.pdf#search=%22%22standard%20of%20identity%22%20margarine%22. 
  4. ↑ Linda McGraw (April 19, 2000). "Biodegradable Hydraulic Fluid Nears Market". USDA. http://www.ars.usda.gov/is/pr/2000/000419.htm. Retrieved 2006-09-29. 
  5. ↑ "Cass Scenic Railroad, West Virginia". GWWCA. http://www.gwrranci.org/gallery/20060824/. Retrieved 2007-07-03. 
  6. ↑ "Ingredients to avoid". The Dog Food Project. http://www.dogfoodproject.com/index.php?page=badingredients. Retrieved 2007-06-26. 
  7. ↑ "Kalu (oil presser)". Banglapedia. http://banglapedia.search.com.bd/HT/K_0050.htm. Retrieved 2006-11-12. 
  8. ↑ Janet Bachmann. "Oilseed Processing for Small-Scale Producers". http://www.attra.org/attra-pub/oilseed.html. Retrieved 2006-07-31. 
  9. ↑ B.L. Axtell from research by R.M. Fairman (1992). "Illipe". Minor oil crops. FAO. http://www.fao.org/es/faodef/fdef14e.htm. Retrieved 2006-11-12. 
  10. ↑ "Ghani". Banglapedia. http://banglapedia.search.com.bd/HT/G_0089.htm. Retrieved 2006-11-12.  A ghani is a traditional Indian oil press, driven by a horse or ox.
  11. ↑ Eisenmenger, Michael; Dunford, Nurhan T.; Eller, Fred; Taylor, Scott; Martinez, Jose (2006). "Pilot-scale supercritical carbon dioxide extraction and fractionation of wheat germ oil". Journal of the American Oil Chemists' Society 83: 863. doi:10.1007/s11746-006-5038-6. 
  12. ↑ January 2009. Oilseeds: World Market and Trade. FOP 1-09. USDA. 2009-01-12. http://www.fas.usda.gov/oilseeds/circular/2009/January/Oilseedsfull0109.pdf. , Table 03: Major Vegetable Oils: World Supply and Distribution at Oilseeds: World Markets and Trade Monthly Circular
  13. ↑ "Soybean Car". Popular Research Topics. Benson Ford Research Center. http://www.thehenryford.org/research/services/populartopics/SoybeanCar/default.asp. Retrieved 2006-10-23. 
  14. ↑ Horstman, Barry M (1999-05-21). "Philip W. Drackett: Earned profits, plaudits". The Cincinnati Post (E. W. Scripps Company). Archived from the original on 2005-12-05. http://web.archive.org/web/20051205202014/http://www.cincypost.com/living/1999/drack052199.html. Retrieved 2006-10-22. 
  15. ↑ "Canola oil". http://www.fda.gov/bbs/topics/ANSWERS/ANS00198.html. Retrieved 2006-07-31. 
  16. ↑ "Waste cooking oil from catering premises". http://www.food.gov.uk/foodindustry/guidancenotes/foodguid/wastecookingoil. Retrieved 2006-07-31. 
  17. ↑ Emily Sonestedt, Ulrika Ericson, Bo Gullberg, Kerstin Skog, Håkan Olsson, Elisabet Wirfält (2008). "Do both heterocyclic amines and omega-6 polyunsaturated fatty acids contribute to the incidence of breast cancer in postmenopausal women of the Malmö diet and cancer cohort?". The International Journal of Cancer (UICC International Union Against Cancer) 123 (7): 1637–1643. doi:10.1002/ijc.23394. PMID 10970215. 
  18. ↑ Berquin IM, Min Y, Wu R, et al. (July 2007). "Modulation of prostate cancer genetic risk by omega-3 and omega-6 fatty acids". The Journal of Clinical Investigation 117 (7): 1866–75. doi:10.1172/JCI31494. PMID 17607361. 
  19. ↑ Mensink RP, Temme EH, Hornstra G (December 1994). "Dietary saturated and trans fatty acids and lipoprotein metabolism". Annals of Medicine 26 (6): 461–4. doi:10.3109/07853899409148369. PMID 7695873. 
  20. ↑ Idris CA, Sundram K (2002). "Effect of dietary cholesterol, trans and saturated fatty acids on serum lipoproteins in non-human primates". Asia Pacific Journal of Clinical Nutrition 11 (Suppl 7): S408–15. doi:10.1046/j.1440-6047.11.s.7.12.x. PMID 12492627. 
  21. ↑ Jonnalagadda SS, Trautwein EA, Hayes KC (May 1995). "Dietary fats rich in saturated fatty acids (12:0, 14:0, and 16:0) enhance gallstone formation relative to monounsaturated fat (18:1) in cholesterol-fed hamsters". Lipids 30 (5): 415–24. doi:10.1007/BF02536299. PMID 7637561. 
  22. ↑ Kromhout D, Menotti A, Bloemberg B, et al. (May 1995). "Dietary saturated and trans fatty acids and cholesterol and 25-year mortality from coronary heart disease: the Seven Countries Study". Preventive Medicine 24 (3): 308–15. doi:10.1006/pmed.1995.1049. PMID 7644455. 
  23. ↑ Khosla P, Hajri T, Pronczuk A, Hayes KC (March 1997). "Decreasing dietary lauric and myristic acids improves plasma lipids more favorably than decreasing dietary palmitic acid in rhesus monkeys fed AHA step 1 type diets". The Journal of Nutrition 127 (3): 525S–530S. PMID 9082040. http://jn.nutrition.org/cgi/pmidlookup?view=long&pmid=9082040. 
  24. ↑ Nicolosi RJ (May 1997). "Dietary fat saturation effects on low-density-lipoprotein concentrations and metabolism in various animal models". The American Journal of Clinical Nutrition 65 (5 Suppl): 1617S–1627S. PMID 9129502. http://www.ajcn.org/cgi/pmidlookup?view=long&pmid=9129502. 
  25. ↑ Stewart-Phillips JL, Lough J, Skamene E (July 1988). "Genetically determined susceptibility and resistance to diet-induced atherosclerosis in inbred strains of mice". The Journal of Laboratory and Clinical Medicine 112 (1): 36–42. PMID 3392456. 
  26. ↑ Nikkari ST, Solakivi T, Jaakkola O (1991). "The hyperlipidemic hamster as an atherosclerosis model". Artery 18 (6): 285–90. PMID 1750802. 
  27. ↑ Otto J, Ordovas JM, Smith D, van Dongen D, Nicolosi RJ, Schaefer EJ (April 1995). "Lovastatin inhibits diet induced atherosclerosis in F1B golden Syrian hamsters". Atherosclerosis 114 (1): 19–28. doi:10.1016/0021-9150(94)05457-T. PMID 7605373. 
  28. ↑ Kowala MC, Recce R, Beyer S, Aberg G (February 1995). "Regression of early atherosclerosis in hyperlipidemic hamsters induced by fosinopril and captopril". Journal of Cardiovascular Pharmacology 25 (2): 179–86. doi:10.1097/00005344-199502000-00001. PMID 7752642. 
  29. ↑ An issue highlighted in documentaries such as Dying for a Biscuit on BBC Panorama http://www.bbc.co.uk/programmes/b00r4t3s

Other references

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