Castor oil

The miracle tree, castor or lat. Ricinus communis L belongs to the spurge family (Euphorbiaceae). In temperate climates, the annual plant reaches a height of one to six meters under optimal conditions. In tropical climates, the miracle tree can grow as a perennial plant and then reaches heights of over 12 meters, which is made possible by lignification of the trunk. In temperate climates, the stem is highly branched and has a reddish to greenish color.

The foliage leaves are between 30 and 100cm tall, dark green, or even reddish and palmately divided. The petioles are long stalked, toothed, 5-11 lobed and glandular on the underside.

The plant prefers soil rich in humus and nutrients, which is permeable (no layers of clay, etc.). In growth, the plant requires adequate moisture and temperatures above 20 degrees Celsius (tropical summer rain beneficial), but after a certain period of growth can withstand drought.

The fruit originally comes from Africa or India, where it is also part of the jewelry culture. The plant is already mentioned in the Old Testament. Thanks to its adaptability, it can also be found in the European climate and is increasingly used here as an ornamental plant. Worldwide cultivation areas for oil production are found in India, USA, Europe and South America. The main producers are India and Brazil.

The plant blooms in Europe from August to October. It bears about 35cm long racemose to rispy inflorescences. Male flowers are clustered among terminal female flowers, classifying the overall flower as mixed-sex, or monoecious. After pollination, spiny, red, closed/split fruits, about three cm in size, form and are ejected. Today's cultivated varieties do not eject the seeds to reduce loss at harvest. Depending on the variety, climate and soil conditions, yields can be expected to range from 500-2000 kg. The fruits are arranged in bunches and resemble the appearance of a chestnut fruit.

During harvesting, the fruits are harvested by hand and then dried. The drying process causes the skin of the fruit to burst, releasing the three seeds contained within. Each seed, in turn, has the shape of a bean with a width of 6-9mm and a length of 8-14mm. The reddish brown to silvery seeds are marbled and shiny. 

Depending on the variety and size of the beans can be assumed approximately the following content: 45% oil; 20% protein, 18% crude fiber and ash. The seed coat contains the toxic protein ricin, which can only be deactivated by heat. Despite the subsequent heating of the oil, the hulls are removed before pressing. Depending on the desired quality, there are three production methods: cold-hot pressing and extraction with organic solvents.

In cold pressing, the seeds are pressed without the addition of heat. In hot pressing, the seeds are heated before pressing or during the pressing process. The yield can thus be significantly increased compared to cold pressing. The remaining press cake still contains about 10% oil and can be further extracted with organic solvents. The oil content can be reduced to <1% with this process. Once the organic solvent is removed, an oil of reduced quality remains. The press cake is used as fertilizer or is further processed into animal feed by special processes (removal of ricin is essential).

Unlike the production of most oils, each quality stage of the oil (including that from cold pressing) must be refined to remove the toxic ricin. The oil is degummed, deacidified, steam treated and centrifuged with the goal of removing harmful proteins and water. If a particularly pure oil is desired, the oil can be bleached with additives to achieve a light color. Special heat processes can even be used to remove the slightly herbaceous, woody odor.

The viscous castor oil consists of 75% triricinolein, a triglyceride, which chemically has an unsaturated fatty acid (ricinoleic acid) and a hydroxyl group. These chemical groups, in addition to the glycerol backbone they contain, allow a wide range of chemical reactions to take place.

Castor oil has a largely temperature-dependent viscosity with high temperature resistance. It is not distillable and tends to decompose at over 250 degrees Celsius. Its density is surprisingly high at 0.96 g/ml, as evidenced by its high viscosity (about 100mPas). In addition, the oil has a high polarity and is highly soluble in ethanol and ether.

In engineering, it is used for this reason as an additive in lubricants in mechanical engineering, internal combustion engines or jet engines. If the triricinolein is alkaline cleaved, sebacic acid can be obtained via certain modifications, which is used as a starting product for the production of polyamides or plasticizers in the plastics industry.

The oil has a good penetrating capacity into the cornea and forms there a mechanical protection against water and hydrophilic pollutants. Drying of the skin is thus reduced, allowing sensitive areas such as scars or small fissures to heal better. Castor oil is therefore also used as an emollient, i.e. a substance that makes the skin softer and more supple.

In pharmacy, the oil is mixed with ethanol, if necessary, and used for dandruff, age spots, hemorrhoids and scarring. The cosmetics industry also takes advantage of the oil and uses it in hair care products, bath oils and hair brighteners (including eye lashes).

Due to its high polarity and viscosity, the oil is used as an active ingredient carrier in medical applications on the eye. The active ingredient thus remains longer on the eye and does not flow off too quickly. In addition to this depot effect, the oil can easily be heated above 100 degrees Celsius, which makes additional preservatives in the eye drops unnecessary. For these reasons, the oil is also used as an additive or even carrier of drugs in some parenteral products.

Orally ingested castor oil is processed in the small intestine into ricinoleic acid, which has an anti-absorptive and secretagogue effect. Together with the bile salts and the associated contraction of the small intestine, this results in softening of the stool, which results in a laxative effect. Castor oil has therefore been used as a laxative for several centuries. Since the effect is very variable in time, does not occur when fat digestion is disturbed and additionally has an irritating effect on the digestive tract, it is no longer used today. Especially during pregnancy and lactation, this laxative is not recommended because it can induce labor pains. Newer laxatives can be dosed better and have fewer side effects.

The oil can also be found under the following synonyms: Castor oil, Christ palm oil, palmachristi oil, castor oil, oleum ricini virginale.