Castor oil plant
The castor plant (Ricinus communis), also known as the miracle tree, is cultivated mainly in the tropics and is also found in northern regions of the globe.
In the tropics, this plant grows like a tree up to a height of 10 meters; however, in cooler climates they only grow as annuals in the wild.
The oil of this plant has been used as fuel dating as far back as ancient Egypt. Today, castor oil is one of the most important industrial oils on Earth.
This ancient and important oil plant originates from India, Africa, the Middle East and the tropics. Today, it is common in many other countries. Also enjoyed as an ornamental, the castor plant is mostly cultivated as a source of oil.
Though China and Brazil are top producers of the miracle tree, India leads the pack with 60% of world production. Large quantities of castor oil seeds are also produced in Ethiopia, Paraguay, Thailand, Vietnam, South Africa, Angola and the Philippines.
Cultivation and components
The castor plant is a commonly found in regions of the tropics with summer rainfall. It prefers full sun and requires a hot (20-25°C) and windless climate. Humus and nutrient-rich, well-drained and moist soil promotes the growth and yield of the plant, but they also grow well in relatively dry conditions.
Climatic conditions have particular influence on the growth of the castor plant.
In temperate and moderate climate zones it can only be cultivated as an annual plant that grows to a maximum height of 7 meters.
In tropical regions, however, they grow incredibly fast and can reach up to 13 meter in just a few years.
Depending on the variety, soil conditions and climatic conditions, castor plants produce anywhere from 450 to 2000 kg of oil per hectare.
The red-brown and spiked fruit of the miracle tree contains three reddish brown, marbled and bean-shaped seeds. They contain 40-50% oil, 14-22% protein, 15 -18% crude fiber and 2-3% ash. Castor plant seeds also contain the allergen CB-1A.250 and two toxins (approx. 0.03-0.15% pyridine alkaloid ricinine and approx. 3% heat-sensitive, polar and highly toxic ricin protein).
Recinin attacks the liver and kidneys in humans. Even small amounts can lead to death. The polypeptide ricin (lectin) is also a toxic protein that occurs in the seed coats. It is soluble in water but fat insoluble. It is easily removed from castor oil using heat for example.
Properties and durability
The clear, yellowish castor oil is a flammable, thick and viscous liquid with a characteristic herbaceous and woody smell. Although practically tasteless, it still has a light and somewhat unpleasant taste that is unique to castor oil.
The solidification range of this oil is somewhere between -13-20° C. The melting point is about -5° C and the flash point about 229° C. In addition, it is one of densest oils and does not require distillation because it decomposes at heats as low as 250° C.
It belongs to the group of non-drying oils. It thickens when exposed to the air, but does not harden in thin films. Due to its high content of hydroxy fatty acids, this fat-insoluble oil exhibits a high polarity and is, therefore, freely soluble in ethanol in combination with aliphatic hydrocarbons; however, it does not mix easily.
Castor oil contains about 80-85% of the unsaturated triglyceride ricinoleic acid (triricinolein) as well as glycerides of various C18 fatty acids and more volatile compounds such as acetic acid, heptanal, octane, hexanal, stryene, alpha-pinene and cyclohexane carboxylic acid. The fatty acid composition of the oil is made up of approximately 77-83% ricinoleic acid, 3-5% linoleic acid, approximately 4-9% oleic acid, 1-2% palmitic acid and 1-3% stearic acid. It also contains traces of vaccenic acid as well as alpha-linolenic, arachidic and eicosenoic acids.
Other components of castor oil include free fatty acids, anywhere from 0.75 to 3.0%, a water content of 0.25-0.5% and miscellaneous impurities ranging from 0.01-0.2%.
The shelf-life of the castor oil is usually 6-8 months.
Pharmaceuticals and medicine
Refined castor oil is used as a laxative for constipation or for cleansing the bowels and - due to its relatively high polarity - as a good solvent for numerous pharmaceutical products.
Castor oil is used as an additive in eye drops due to its high viscosity and low content of nutrients for microorganisms.
It is used for injection purposes for administering lipophilic drugs that cannot be taken orally. In addition to its topical use, this oil is often used for the medication of in the form of sex hormones in oily solutions for a residual effect.
The oil forms a mechanical protection against water and hydrophilic contaminants and is used to safely and quickly repair cracks and fissures.
In addition, castor oil is used for its excellent solubility in ethanol and as a fat additive in spirits and other alcohols. Warts and ringworm are also treatable with castor oil.
In obstetrics, this oil is also administered as a "labor cocktail" to induce labor contractions. Moreover, ricin is currently be tested as a cancer therapy due to its cytostatic effect on cancerous tumor cells.
In folk medicine
In natural medicine, castor oil is used to relieve chest infections, loosen stiffened arthritic joints, increase the function of congested lymph glands, and strengthen the immune system.
In addition, castor oil is used to control herpes outbreaks and alleviate spasms in the abdomen. Hot castor oil supposedly has a positive impact on colitis, helps prevent the formation of ulcers, and stimulates the digestive system.
Castor oil is frequently used in products in the cosmetics industry, such as hair dyes, hair care products, and mascaras because of its high viscosity and its high solubility in ethanol.
In addition, it is added to bath oils with emulsifiers to relieve dry skin. Due to its high penetrability of intercellular spaces, e.g. in callused skin, it is popular for treating dandruff, scars, liver spots and hemorrhoids.
Castor oil is also used as a raw material in the manufacture of lipsticks, shampoos and cosmetics, due especially to the moisturizing and emollient effects on the skin and hair of the triricinolein contained therein.
In engineering, castor oil can be used for the manufacture of soaps, paints, dyes, inks, waxes, polishes, cold-resistant plastic, the production of nylon, pharmaceuticals and fragrances.
Castor oil can be used as an engine lubricant (e.g. in jet engines) or as brake fluid due to its typically constant viscosity regardless of temperature.
Thanks to unique properties that make it a natural polyol, castor oil is essential to the manufacture of polyurethane plastics. Its natural hydroxyl functionality (OH) makes it suitable for reactions with di- or polyisocyanates for polyurethane polymers.
This property, among others, is crucial for the production of polyurethane foams (e.g. upholstery, mattresses, construction foams), casting resins and adhesives.
Castor oil is also a useful binding agent for coatings, paints, varnish, linoleum and printing inks. Furthermore, this oil is a basic material for polyamides and polystyrenes and is suitable for the production of sebacic acid, an important ingredient in fabric softeners.
It is also used in the production of Turkey red oil, which is used as a dye (stain) in the textile industry for its wetting properties and emulsifiability.
Furthermore, castor oil can be helpful after transesterification in the production of biodiesel.
It is also used in the manufacture of flavorings and fragrances after the pyrolytic decomposition of the oil into heptanal and undecenoic acids.
Undecen acid ester can be processed into a major polyamide, which serves as a high-performance polymer for fibers and for various technical applications, particularly for cable coatings and automobiles.
Finally, polyester can be derived from castor oil through the polycondensation of citric and ricinoleic acids. Dehydration of the inter-reacting monomers catalyzes the synthesis of polyester, which is finally converted into a brownish, sticky, water-insoluble resin.
Oilcakes, which are the byproduct of oil pressing, are detoxified through a heat inactivation process and frequently used in the manufacture of animal feed or organic fertilizers.
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Due to its extremely toxic constituents, the miracle tree is recognized in the Guinness Book of Records 2007 as the most poisonous plant in the world.
Ricin is found in all parts of the plant, is highly toxic, and has an insecticidal effect. Just 3-10 seeds can be fatal to an adult. One single seed is life threatening to a child.
Especially dangerous is the delay in the onset of symptoms of poisoning, which typically occur after several hours and sometimes days.
Ricin may be removed, however, using advanced pressure and extraction methods.
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