Cottonseed oil is a cooking oil extracted from the seeds of cotton plants of various species, mainly Gossypium hirsutum and Gossypium herbaceum, that are grown for cotton fiber, animal feed, and oil.
Cotton seed has a similar structure to other oilseeds such as sunflower seed, having an oil-bearing kernel surrounded by a hard outer hull; in processing, the oil is extracted from the kernel. Cottonseed oil is used for salad oil, mayonnaise, salad dressing, and similar products because of its flavor stability.
Its fatty acid profile generally consists of 70% unsaturated fatty acids (18% monounsaturated, and 52% polyunsaturated), 26% saturated fatty acids. When it is fully hydrogenated, its profile is 94% saturated fat and 2% unsaturated fatty acids (1.5% monounsaturated, and 0.5% polyunsaturated). According to the cottonseed oil industry, cottonseed oil does not need to be hydrogenated as much as other polyunsaturated oils to achieve similar results.
Gossypol is a toxic, yellow, polyphenolic compound produced by cotton and other members of the order Malvaceae, such as okra. This naturally occurring coloured compound is found in tiny glands in the seed, leaf, stem, tap root bark, and root of the cotton plant. The adaptive function of the compound facilitates natural insect resistance. The three key steps of refining, bleaching, and deodorization in producing finished oil act to eliminate the gossypol level. Ferric chloride is often used to decolorize cotton seed oil.
Comparison to other vegetable oils
|Monounsaturated fatty acids||Polyunsaturated fatty acids||Smoke point|
|Total mono||Oleic acid
|Total poly||linolenic acid
|Avocado||11.6||70.6||13.5||1||12.5||249 °C (480 °F)|
|Canola||7.4||63.3||61.8||28.1||9.1||18.6||238 °C (460 °F)|
|Coconut||82.5||6.3||6||1.7||175 °C (347 °F)|
232 °C (450 °F)
|Cottonseed||25.9||17.8||19||51.9||1||54||216 °C (420 °F)|
107 °C (225 °F)
166 °C (330 °F)
|Olive||13.8||73.0||71.3||10.5||0.7||9.8||193 °C (380 °F)|
|Palm||49.3||37.0||40||9.3||0.2||9.1||235 °C (455 °F)|
|Peanut||20.3||48.1||46.5||31.5||31.4||232 °C (450 °F)|
|Safflower||7.5||75.2||75.2||12.8||0||12.8||212 °C (414 °F)|
|Soybean||15.6||22.8||22.6||57.7||7||51||238 °C (460 °F)|
|Sunflower (< 60% linoleic)||10.1||45.4||45.3||40.1||0.2||39.8||
227 °C (440 °F)
|Sunflower (> 70% oleic)||9.9||83.7||82.6||3.8||0.2||3.6||
227 °C (440 °F)
|Values as percent (%) by weight of total fat.|
Once processed, cottonseed oil has a mild taste and appears generally clear with a light golden color, the amount of color depending on the amount of refining. It has a relatively high smoke point as a frying medium. Density ranges from 0.917 g/cm3 to 0.933 g/cm3. Like other long-chain fatty acid oils, cottonseed oil has a smoke point of about 450 °F (232 °C), and is high in tocopherols, which also contribute its stability, giving products that contain it a long shelf life, hence manufacturers' proclivity to use it in packaged goods.
The by-product of cotton processing, cottonseed was considered virtually worthless before the late 19th century. While cotton production expanded throughout the 17th, 18th, and mid 19th centuries, a largely worthless stock of cottonseed grew. Although some of the seed was used for planting, fertilizer, and animal feed, the majority was left to rot or was illegally dumped into rivers.
In the 1820s and 1830s Europe experienced fats and oils shortages due to rapid population expansion during the Industrial Revolution and the after-effects of the British blockade during the Napoleonic Wars. The increased demand for fats and oils, coupled with a decreasing supply caused prices to rise sharply. Consequently, many Europeans could not afford to buy the fats and oils they had used for cooking and for lighting. Many United States entrepreneurs tried to take advantage of the increasing European demand for oils and America’s increasingly large supply of cottonseed by crushing the seed for oil. But separating the seed hull from the seed meat proved difficult and most of these ventures failed within a few years. This problem was resolved in 1857, when William Fee invented a huller, which effectively separated the tough hulls from the meats of cottonseed. With this new invention, cottonseed oil began to be used for illumination purposes in lamps to supplement increasingly expensive whale oil and lard. But by 1859, this use came to end as the petroleum industry emerged.
Cottonseed oil then began to be used illegally to fortify animal fats and lards. Initially, meat packers secretly added cottonseed oil to the pure fats, but this practice was uncovered in 1884. Armour and Company, an American meatpacking and food processing company, sought to corner the lard market and realized that it had purchased more lard than the existing hog population could have produced. A congressional investigation followed, and legislation was passed that required products fortified with cottonseed oil to be labeled as ‘‘lard compound.” Similarly, cottonseed oil was often blended with olive oil. Once the practice was exposed, many countries put import tariffs on American olive oil and Italy banned the product completely in 1883. Both of these regulatory schemes depressed cottonseed oil sales and exports, once again creating an oversupply of cottonseed oil, which decreased its value.
It was cottonseed's depressed value that led a newly formed Procter & Gamble to utilize its oil. The Panic of 1837 caused the two brothers-in-law to merge their candlestick and soap manufacturing businesses in an effort to minimize costs and weather the bear market. Looking for a replacement for expensive animal fats in production, the brothers finally settled on cottonseed oil. Procter & Gamble cornered the cottonseed oil market to circumvent the meat packer's monopoly on the price. But as electricity emerged, the demand for candles decreased. Procter and Gamble then found an edible use for cottonseed oil. Through patented technology, the brothers were able to hydrogenate cottonseed oil and develop a substance that closely resembled lard. In 1911, Procter & Gamble launched an aggressive marketing campaign to publicize its new product, Crisco, a vegetable shortening that could be used in place of lard. Crisco placed ads in major newspapers advertising that the product was "easier on digestion...a healthier alternative to cooking with animal fats. . . and more economical than butter.” The company also gave away free cookbooks, with every recipe calling for Crisco. By the 1920s the company developed cookbooks for specific ethnicities in their native tongues. Additionally, Crisco starting airing radio cooking programs. Similarly, in 1899 David Wesson, a food chemist, developed deodorized cottonseed oil, Wesson cooking oil. Wesson Oil also was marketed heavily and became quite popular too.
Over the next 30 years cottonseed oil became the pre-eminent oil in the United States. Crisco and Wesson oil became direct substitutes for lard and other more expensive oils in baking, frying, sautéing, and salad dressings. But by World War Two cottonseed oil shortages forced the utilization of another direct substitute, soybean oil. By 1944, soybean oil production outranked cottonseed oil production due to cottonseed shortages and soybean oil costs falling below that of cottonseed oil. By 1950, soybean oil replaced cottonseed oil in the use of shortenings like Crisco due to soybeans comparatively low price. Prices for cottonseed were also increased by the replacement of cotton acreage by corn and soybeans, a trend fueled in large part by the boom in demand for corn syrup and ethanol. Cottonseed oil and production continued to decline throughout the mid and late 20th century.
In the mid to late 2000s, the consumer trend of avoiding trans fats, and mandatory labeling of trans fats in some jurisdictions, sparked an increase in the consumption of cottonseed oil, with some health experts:220 and public health agencies recommending it as a healthy oil. Crisco and other producers have been able to reformulate cottonseed oil so it contains little to no trans fats. Still, some health experts claim that cottonseed oil’s high ratio of polyunsaturated fats to monounsaturated fats and processed nature make it unhealthy.
Cottonseed oil in Canada must be pressed from the seed of the Gossypium plant. As a single source vegetable oil, 100% cottonseed oil must appear as “cottonseed oil” on the labels of any products sold.
Cottonseed oil sold in the marketplace as an edible product must be processed and refined to eliminate specific components that could present as a food safety hazard. In particular gossypol, a natural pigment present in the cotton seeds that acts as a natural defense mechanism to insects and other predators, can also act as a toxin to humans, and can lead to infertility in men.
Cottonseed oil, like other vegetable oils, is extracted from the seed of the plant, through either mechanical processes such as crushing or pressing, by or chemical processes such as solvent extraction. Cottonseed oil however, is most commonly extracted commercially via solvent extraction.
Once the crude oil is extracted, it must be processed and refined before it can be used for consumption, in order to remove impurities, including free fatty acids (FFA), phospholipids, pigments and volatile compounds.
Degumming is the first step in the refining process to remove phospholipids, gums, waxes and other impurities from the crude oil. The oil is treated with water or dilute acids such as phosphoric acid, which exploits the fact that the phospholipids are attracted to water because of their amphipathic nature, and turns the lipids into hydrated gums. These gums are insoluble in oil and are then separated from the oil using centrifuges. The separated gums are then dried and manufactured into emulsifying agents such as lecithin.
The second step in the refining process is the separation of the free fatty acids (FFA) from the oil through alkaline neutralization. Depending on the type of oil being processed, there can be either two or three stages during neutralization, where three stages are done to produce a higher quality oil. Cottonseed oil goes through all three stages of neutralization.
The first stage of neutralization occurs when caustic soda, or sodium hydroxide is added to the oil after being pumped through a strainer and heated to 133ºc. Saponification reaction which neutralizes the oil occurs when the mixture is blended.
During saponification, the positive charge from free fatty acids (FFA) reacts with negatively charged hydroxyl group in the caustic soda to form soap and glycerol. This is known as soapstock and will be separated from the oil.
The second stage of neutralization is the repetition of stage one with the addition of more caustic soda to the mixture.
The final stage is a second wash with water to minimize the level of residual soap in the mixture.
The third stage in the refining process is the removal of any residual soap, gums or pigments through bleaching. The most common bleaching agent employed is bleaching earth, a type of bentonite clay. Once the clay is added, the mixture is agitated, which allows the clay to bind the contaminants in the oil, either physically (eg. Van der Waal forces) or chemically (chemisorption). The mixture is then filtered to remove the clay with the bound contaminants.
The fourth stage in the refining process is deodorization to remove any volatile substances. The molecules are distilled using high pressure steam injected through a vacuum system.
The fifth stage in the refining process is winterization to remove the saturated triacylglycerols to prevent the oil product from solidifying at low temperatures. The processed oil is stored at a cool environment where the temperature is kept below 5ºc.
Through winterization, the oil will separate into liquid and solid fractions. The solid fraction will be crystallized due to the presence of saturated triacylglycerols. The two fractions are then separated by filtration.
Use in food
Cottonseed oil has traditionally been used in foods such as potato chips and was for many years a primary ingredient in Crisco, the shortening product. The current formulation of Crisco includes no cottonseed oil. Significantly less expensive than olive oil or canola oil, cottonseed oil is a popular frying oil for the restaurant and snack-food manufacturing industries.
Cottonseed oil is used in the production of edible food products such as cooking oils, salad oils, margarines and shortenings. In the United States, cottonseed oil is used in Procter & Gamble’s Olestra and Olein products as a type of non-digestible fat substitutes used to create creamy textures and rich flavours in fried founds.
For agricultural applications, cottonseed oil generally has the greatest insecticide power among all the vegetable oils. They are traditionally used because of their effectiveness in “hard to treat” pest problems in fruit trees. Cottonseed oil can also be mixed with other insecticides to provide a broader spectrum and increased control on pests. Spider mites, whiteflies and young stages of scales are common pests that can be controlled using cottonseed oil.
Use as insecticide
In an agricultural context, the toxicity of untreated cottonseed oil may be considered beneficial: Oils, including vegetable oils, have been used for centuries to control insect and mite pests. More recently, cottonseed oil has been used to protect the trunks of apple trees from the apple clearwing moth, which burrows into the trees' bark, potentially killing them. This oil has been generally considered the most insecticidal of vegetable oils.
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