Castor oil

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Castor beans Castor beans.jpg
Castor beans
A bottle of castor oil Castor oil.jpg
A bottle of castor oil

Castor oil is a vegetable oil pressed from castor beans. [1] The name probably comes from its use as a replacement for castoreum. [2]

Vegetable oil triglyceride extracted from a plant

Vegetable oils, or vegetable fats, are fats extracted from seeds, or less often, from other parts of fruits. Like animal fats, vegetable fats are mixtures of triglycerides. Soybean oil, rapeseed oil, and cocoa butter are examples of fats from seeds. Olive oil, palm oil, and rice bran oil are example of fats from other parts of fruits. In common usage, vegetable oil may refer exclusively to vegetable fats which are liquid at room temperature.

Castoreum chemical substance

Castoreum is a yellowish exudate from the castor sacs of the mature North American beaver and the European beaver.

Contents

Castor oil is a colourless to very pale yellow liquid with a distinct taste and odor. Its boiling point is 313 °C (595 °F) and its density is 961 kg/m3. [3] It is a triglyceride in which approximately 90 percent of fatty acid chains are ricinoleates. Oleate and linoleates are the other significant components.

Boiling point temperature

The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.

The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume:

Triglyceride any ester of glycerol having all three hydroxyl groups esterified with fatty acids

A triglyceride is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other animals, as well as vegetable fat. They are also present in the blood to enable the bidirectional transference of adipose fat and blood glucose from the liver, and are a major component of human skin oils.

Castor oil and its derivatives are used in the manufacturing of soaps, lubricants, hydraulic and brake fluids, paints, dyes, coatings, inks, cold resistant plastics, waxes and polishes, nylon, pharmaceuticals and perfumes. [4]

Soap sodium salt of fatty acids ( long chain carboxylic acids ), used for washing and cleaning

Soap is the term for a salt of a fatty acid or for a variety of cleansing and lubricating products produced from such a substance. Household uses for soaps include washing, bathing, and other types of housekeeping, where soaps act as surfactants, emulsifying oils to enable them to be carried away by water. In industry, they are used as thickeners, components of some lubricants, and precursors to catalysts.

A lubricant is a substance, usually organic, introduced to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces. The property of reducing friction is known as lubricity.

Brake fluid is a type of hydraulic fluid used in hydraulic brake and hydraulic clutch applications in automobiles, motorcycles, light trucks, and some bicycles. It is used to transfer force into pressure, and to amplify braking force. It works because liquids are not appreciably compressible.

Composition

Structure of the major component of castor oil: triester of glycerol and ricinoleic acid Castor oil (Main Component Structural Formulae) V2.svg
Structure of the major component of castor oil: triester of glycerol and ricinoleic acid

Castor oil is well known as a source of ricinoleic acid, a monounsaturated, 18-carbon fatty acid. Among fatty acids, ricinoleic acid is unusual in that it has a hydroxyl functional group on the 12th carbon. This functional group causes ricinoleic acid (and castor oil) to be more polar than most fats. The chemical reactivity of the alcohol group also allows chemical derivatization that is not possible with most other seed oils. Because of its ricinoleic acid content, castor oil is a valuable chemical in feedstocks, commanding a higher price than other seed oils. As an example, in July 2007, Indian castor oil sold for about US$0.90 per kilogram (US$0.41 per pound) [5] whereas U.S. soybean, sunflower and canola oils sold for about US$0.30 per kilogram (US$0.14 per pound). [6]

Ricinoleic acid chemical compound

Ricinoleic acid, formally called 12-hydroxy-9-cis-octadecenoic acid is a fatty acid. It is an unsaturated omega-9 fatty acid and a hydroxy acid. It is a major component of the seed oil obtained from mature Castor plant seeds or in sclerotium of ergot. About 90% of the fatty acid content in castor oil is the triglyceride formed from ricinoleic acid.

An unsaturated fat is a fat or fatty acid in which there is at least one double bond within the fatty acid chain. A fatty acid chain is monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond.

Fatty acid carboxylic acid with a long aliphatic chain, which is either saturated or unsaturated

In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with a long aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually not found in organisms, but instead as three main classes of esters: triglycerides, phospholipids, and cholesterol esters. In any of these forms, fatty acids are both important dietary sources of fuel for animals and they are important structural components for cells.

Average composition of castor seed oil / fatty acid chains
Acid nameAverage Percentage Range
Ricinoleic acid 85–95
Oleic acid 2–6
Linoleic acid 1–5
α-Linolenic acid 0.5–1  
Stearic acid 0.5–1  
Palmitic acid 0.5–1  
Dihydroxystearic acid 0.3–0.5
Others0.2– 0.5

Uses

Annually 270,000–360,000 tonnes (600–800 million pounds) of castor oil are produced for a variety of uses. [4]

Food and preservative

In the food industry, castor oil (food grade) is used in food additives, flavorings, candy (e.g., polyglycerol polyricinoleate or PGPR in chocolate), [7] as a mold inhibitor, and in packaging. Polyoxyethylated castor oil (e.g., Kolliphor EL) [8] is also used in the food industries. [9]

Polyglycerol polyricinoleate chemical compound

Polyglycerol polyricinoleate (PGPR), E476, is an emulsifier made from glycerol and fatty acids. In chocolate, compound chocolate and similar coatings, PGPR is mainly used with another substance like lecithin to reduce viscosity. It is used at low levels, and works by decreasing the friction between the solid particles in molten chocolate, reducing the yield stress so that it flows more easily, approaching the behaviour of a Newtonian fluid. It can also be used as an emulsifier in spreads and in salad dressings, or to improve the texture of baked goods. It is made up of a short chain of glycerol molecules connected by ether bonds, with ricinoleic acid side chains connected by ester bonds.

Kolliphor EL, formerly known as Cremophor EL, is the registered trademark of BASF Corp. for its version of polyethoxylated castor oil. It is prepared by reacting 35 moles of ethylene oxide with each mole of castor oil. The resulting product is a mixture : the major component is the material in which the hydroxyl groups of the castor oil triglyceride have ethoxylated with ethylene oxide to form polyethylene glycol ethers. Minor components are the polyethyelene glycol esters of ricinoleic acid, polyethyelene glycols and polyethyelene glycol ethers of glycerol. Kolliphor EL is a synthetic, nonionic surfactant used to stabilize emulsions of nonpolar materials in water.

In India, Pakistan and Nepal food grains are preserved by the application of castor oil. It stops rice, wheat, and pulses from rotting. For example, the legume pigeon pea is commonly available coated in oil for extended storage.

Medicine

Advertisement of castor oil as a medicine by Scott & Bowne Company, 19th century Scott & Bowne's Palatable Castor Oil.jpg
Advertisement of castor oil as a medicine by Scott & Bowne Company, 19th century

Use of castor oil as a laxative is attested to in the circa 1550 BC Ebers Papyrus, [10] and was in use for several centuries prior. [11] The United States Food and Drug Administration (FDA) has categorized castor oil as "generally recognized as safe and effective" (GRASE) for over-the-counter use as a laxative with its major site of action the small intestine where it is digested into ricinoleic acid. [12]

Despite castor oil being widely used to induce labor in pregnant women, to date there is not enough research to show whether it is effective to dilate the cervix or induce labor. [13]

Therapeutically, modern drugs are rarely given in a pure chemical state, so most active ingredients are combined with excipients or additives. Castor oil, or a castor oil derivative such as Kolliphor EL (polyethoxylated castor oil, a nonionic surfactant), is added to many modern drugs, including:

Castor oil is also one of the components of Vishnevsky liniment. [23]

Alternative medicinal use

In naturopathy castor oil has been promoted as a treatment for a variety of human health conditions, [24] including cysts. [25] The claim has been made that applying it to the skin can help cure cancer. However, according to the American Cancer Society, "available scientific evidence does not support claims that castor oil on the skin cures cancer or any other disease." [26]

Skin and hair care

Castor oil has been used in cosmetic products included in creams and as a moisturizer. It also has been used to enhance hair conditioning in other products and for supposed anti-dandruff properties. [27] Castor oil is a widely popular carrier oil for beard care for the same reasons it is popular for hair. Using castor oil in a beard is ideal since it helps with anti-dandruff but as well as its high linoleic acid levels. This fatty acid restores dry follicles, adds shine and promotes follicle growth. [28]

Coatings

Castor oil is used as a bio-based polyol in the polyurethane industry. The average functionality (number of hydroxyl groups per triglyceride molecule) of castor oil is 2.7, so it is widely used as a rigid polyol and in coatings. [1] One particular use is in a polyurethane concrete where a Castor Oil emulsion is reacted with an isocyanate (usually polymeric MDI Methylene diphenyl diisocyanate) and a Cement and Construction aggregate. This is applied fairly thickly as a slurry which is self-levelling. This base is usually further coated with other systems to build a resilient floor [29] [30] .

It is not a drying oil, meaning that it has a low reactivity with air compared to oils such as linseed oil and tung oil. Dehydration of castor oil yields linoleic acids, which do have drying properties [1] . In this process, the OH group on the ricinoleic acid along with a hydrogen from the next carbon atom are removed yielding a double bond which then has oxidative cross-linking properties yielding the drying oil.

Precursor to industrial chemicals

Castor oil can be broken down into other chemical compounds that have numerous applications. [31] [32] [33] Transesterification followed by steam cracking gives undecylenic acid, a precursor to specialized polymer nylon 11, and heptanal, a component in fragrances. [34] Breakdown of castor oil in strong base gives 2-octanol, both a fragrance component and a specialized solvent, and the dicarboxylic acid sebacic acid. Hydrogenation of castor oil saturates the alkenes, giving a waxy lubricant. [1] . Castor oil may be epoxidized by reacting the OH groups with Epichlorohydrin to make the triglycidyl ether of castor oil which is useful in epoxy technology [35] . This is available commercially as Heloxy 505 from Hexion and others [36] .

The production of lithium grease consumes a significant amount of castor oil. Hydrogenation and saponification of castor oil yields 12-hydroxystearic acid which is then reacted with lithium hydroxide or lithium carbonate to give high performance lubricant grease. [37]

Since it has a relatively high dielectric constant (4.7), highly refined and dried castor oil is sometimes used as a dielectric fluid within high performance high voltage capacitors.

Lubrication

Vegetable oils like castor oil are typically unattractive alternatives to petroleum-derived lubricants because of their poor oxidative stability. [38] [39] Castor oil has better low-temperature viscosity properties and high-temperature lubrication than most vegetable oils, making it useful as a lubricant in jet, diesel, and racing engines. [40] The viscosity of castor oil at 10 °C is 2,420 centipoise. [41] However, castor oil tends to form gums in a short time, and therefore its usefulness is limited to engines that are regularly rebuilt, such as racing engines. The lubricant company Castrol took its name from castor oil.

Castor oil has been suggested as a lubricant for bicycle pumps because it does not degrade natural rubber seals. [42]

Early aviation and aeromodelling
World War I aviation rotary engines used castor oil as a primary lubricant, mixed with the fuel Le Rhone 9C.jpg
World War I aviation rotary engines used castor oil as a primary lubricant, mixed with the fuel

Castor oil was the preferred lubricant for rotary engines, such as the Gnome engine after that engine's widespread adoption for aviation in Europe in 1909. It was used almost universally in rotary engined Allied aircraft in World War I. Germany had to make do with inferior ersatz oil (a German term for alternative, substitute, replacement) for its rotary engines, which resulted in poor reliability. [43] [44] [45]

The methanol-fueled two-cycle glow plug engines used for aeromodelling, since their adoption by model airplane hobbyists in the 1940s, have used varying percentages of castor oil as a lubricant. It is highly resistant to degradation when the engine has its fuel-air mixture leaned for maximum engine speed. Gummy residues can still be a problem for aeromodelling powerplants lubricated with castor oil, however, usually requiring eventual replacement of ball bearings when the residue accumulates within the engine's bearing races. One British manufacturer of sleeve valved four-cycle model engines has stated the "varnish" created by using castor oil in small percentages can improve the pneumatic seal of the sleeve valve, improving such an engine's performance over time.

Turkey red oil

Turkey red oil, also called sulphonated (or sulfated) castor oil, is made by adding sulfuric acid to vegetable oils, most notably castor oil. [46] It was the first synthetic detergent after ordinary soap. It is used in formulating lubricants, softeners, and dyeing assistants. [47]

Biodiesel

Castor oil, like currently less expensive vegetable oils, can be used as feedstock in the production of biodiesel. The resulting fuel is superior for cold winters, because of its exceptionally low cloud and pour points. [48]

Initiatives to grow more castor for energy production, in preference to other oil crops, are motivated by social considerations. Tropical subsistence farmers would gain a cash crop. [49]

Punishment

Some parents punished children with a dose of castor oil. [50] [51] Physicians recommended against the practice because they did not want medicines associated with punishment. [52]

A heavy dose of castor oil could be used as a humiliating punishment for adults, especially political dissenters. Colonial officials used it in the British Raj (India) to deal with recalcitrant servants. [53] Belgian military officials prescribed heavy doses of castor oil in Belgian Congo as a punishment for being too sick to work. [54]

The most famous use as punishment came in Fascist Italy under Benito Mussolini. It was a favorite tool used by the Blackshirts to intimidate and humiliate their opponents. [55] [56] [57] Political dissidents were force-fed large quantities of castor oil by Fascist squads. This technique was said to have been originated by Gabriele D'Annunzio or Italo Balbo. [58] Victims of this treatment did sometimes die, as the dehydrating effects of the oil-induced diarrhea often complicated the recovery from the nightstick beating they also received along with the castor oil; however, even those victims who survived had to bear the humiliation of the laxative effects resulting from excessive consumption of the oil. [59] Inspired by the Italian Fascists, the Nazi SA used the torture method against German Jews shortly after the appointment of Adolf Hitler as Chancellor of Germany in 1933. [60]

It is said that Mussolini's power was backed by "the bludgeon and castor oil". [59] In lesser quantities, castor oil was also used as an instrument of intimidation, for example, to discourage civilians or soldiers who would call in sick either in the factory or in the military. It took decades after Mussolini's death before the myth of castor oil as a panacea for a wide range of diseases and medical conditions was totally demystified, as it was also widely administered to pregnant women and elderly or mentally ill patients in hospitals in the false belief it had no negative side effects.

Today, the Italian terms manganello and olio di ricino, even used separately, still carry strong political connotations (especially the latter). These words are still used to satirize patronizing politicians, or the authors of disliked legislation. They should be used with caution in common conversation. The terms Usare l'olio di ricino, ("to use castor oil") and usare il manganello ("to use the bludgeon") mean "to coerce or abuse", and can be misunderstood in the absence of proper context.

As a means of punishment or torture, force-feeding castor oil is depicted in the animated cartoon Tom and Jerry, in the Our Gang comedy Shrimps for a Day (1934), and in the movie Amarcord .

Safety

The castor seed contains ricin, a toxic lectin. Heating during the oil extraction process denatures and deactivates the lectin. However, harvesting castor beans may not be without risk. [61] Allergenic compounds found on the plant surface can cause permanent nerve damage, making the harvest of castor beans a human health risk. India, Brazil and China are the major crop producers and the workers suffer harmful side effects from working with these plants. [62] These health issues, in addition to concerns about the toxic byproduct (ricin) from castor oil production, have encouraged the quest for alternative sources for hydroxy fatty acids. [63] [64] Alternatively, some researchers are trying to genetically modify the castor plant to prevent the synthesis of ricin. [65]

Since castor oil is sometimes used to induce labor in full-term pregnancies (scientific evidence of its effectiveness is lacking), [66] consuming castor oil to treat constipation is not considered safe in pregnancies that are not at full term yet, as it may cause contractions of the womb. [67]

See also

Related Research Articles

<i>Ricinus</i> species of plant, Castor oil plant

Ricinus communis, the castor bean or castor oil plant, is a species of perennial flowering plant in the spurge family, Euphorbiaceae. It is the sole species in the monotypic genus, Ricinus, and subtribe, Ricininae. The evolution of castor and its relation to other species are currently being studied using modern genetic tools. It reproduces with a mixed pollination system which favors selfing by geitonogamy but at the same time can be an out-crosser by anemophily or entomophily.

Tallow rendered form of beef or mutton fat

Tallow is a rendered form of beef or mutton fat, and is primarily made up of triglycerides. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation.

Stearic acid chemical compound

Stearic acid ( STEER-ik, stee-ARR-ik) is a saturated fatty acid with an 18-carbon chain and has the IUPAC name octadecanoic acid. It is a waxy solid and its chemical formula is C17H35CO2H. Its name comes from the Greek word στέαρ "stéar", which means tallow. The salts and esters of stearic acid are called stearates. As its ester, stearic acid is one of the most common saturated fatty acids found in nature following palmitic acid. The triglyceride derived from three molecules of stearic acid is called stearin.

Oleic acid monounsaturated omega-9 fatty acid, abbreviated with a lipid number of 18:1 cis-9

Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega-9 fatty acid, abbreviated with a lipid number of 18:1 cis-9. It has the formula CH3(CH2)7CH=CH(CH2)7COOH. The name derives from the Latin word oleum, which means oil. It is the most common fatty acid in nature. Salts of oleic acid are called oleates.

Biodiesel production is the process of producing the biofuel, biodiesel, through the chemical reactions transesterification and esterification. This involves vegetable or animal fats and oils being reacted with short-chain alcohols. The alcohols used should be of low molecular weight, ethanol being one of the most used for its low cost. However, greater conversions into biodiesel can be reached using methanol. Although the transesterification reaction can be catalyzed by either acids or bases the most common means of production is base-catalyzed transesterification. This path has lower reaction times and catalyst cost than those posed by acid catalysis. However, alkaline catalysis has the disadvantage of its high sensitivity to both water and free fatty acids present in the oils.

Gamma-linolenic acid or GLA, is a fatty acid found primarily in vegetable oils. When acting on GLA, Arachidonate 5-lipoxygenase produces no leukotrienes and the conversion by the enzyme of arachidonic acid to leukotrienes is inhibited.

A dicarboxylic acid is an organic compound containing two carboxyl functional groups (−COOH). The general molecular formula for dicarboxylic acids can be written as HO2C−R−CO2H, where R can be aliphatic or aromatic. In general, dicarboxylic acids show similar chemical behavior and reactivity to monocarboxylic acids. Dicarboxylic acids are also used in the preparation of copolymers such as polyamides and polyesters. The most widely used dicarboxylic acid in the industry is adipic acid, which is a precursor used in the production of nylon. Other examples of dicarboxylic acids include aspartic acid and glutamic acid, two amino acids in the human body. The name can be abbreviated to diacid.

Jojoba oil oil produced from the seeds of jojoba

Jojoba oil is the liquid produced in the seed of the Simmondsia chinensis (Jojoba) plant, a shrub, which is native to southern Arizona, southern California, and northwestern Mexico. The oil makes up approximately 50% of the jojoba seed by weight. The terms "jojoba oil" and "jojoba wax" are often used interchangeably because the wax visually appears to be a mobile oil, but as a wax it is composed almost entirely (~97%) of mono-esters of long-chain fatty acids and alcohols, accompanied by only a tiny fraction of triglyceride esters. This composition accounts for its extreme shelf-life stability and extraordinary resistance to high temperatures, compared with true vegetable oils.

Sunflower oil oil pressed from the seed of Helianthus annuus

Sunflower oil is the non-volatile oil pressed from the seeds of sunflower. Sunflower oil is commonly used in food as a frying oil, and in cosmetic formulations as an emollient. The world's total production of sunflower oil in 2014 was nearly 16 million tonnes, with Ukraine and Russia as the largest producers.

Alkyd painting implement

An alkyd is a polyester modified by the addition of fatty acids and other components. They are derived from polyols and a dicarboxylic acid or carboxylic acid anhydride. The term alkyd is a modification of the original name "alcid", reflecting the fact that they are derived from alcohol and organic acids. The inclusion of the fatty acid confers a tendency to form flexible coating. Alkyds are used in paints and in moulds for casting. They are the dominant resin or "binder" in most commercial "oil-based" coatings. Approximately 200,000 tons of alkyd resins are produced each year. The original alkyds were compounds of glycerol and phthalic acid sold under the name Glyptal. These were sold as substitutes for the darker-colored Copal resins, thus creating alkyd varnishes which were much paler in colour. From these, the alkyds we know today were developed.

Natural oil polyols, also known as NOPs or biopolyols, are polyols derived from vegetable oils by several different techniques. The primary use for these materials is in the production of polyurethanes. Most NOPs qualify as biobased products, as defined by the United States Secretary of Agriculture in the Farm Security and Rural Investment Act of 2002.

Nonadecylic acid, or nonadecanoic acid, is a 19-carbon long saturated fatty acid with the chemical formula CH3(CH2)17COOH. It forms salts called nonadecylates. Nonadecylic acid can be found in fats and vegetable oils. It is also used by insects as pheromones.

Cooking oil oil consumed by humans, from vegetable or animal origin

Cooking oil is plant, animal, or synthetic fat used in frying, baking, and other types of cooking. It is also used in food preparation and flavouring not involving heat, such as salad dressings and bread dips, and in this sense might be more accurately termed edible oil.

Methyl ricinoleate is a clear, viscous fluid that is used as a surfactant, cutting fluid additive, lubricant, and plasticizer. It is a plasticizer for cellulosic resins, polyvinyl acetate, and polystyrene. It is a type of fatty acid methyl ester synthesized from castor oil and methyl alcohol.

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Further reading