Castor oil is a non-food oil used in many sectors for thousands of years (medicine, automotive, cosmetics…). In Ancient Egypt, people used it as fuel to light lamps but also as a natural remedy to stimulate labor before giving birth. Today, it is found in a plethora of skin and hair care products, mainly for its soothing and strengthening properties. Let's take a look at the castor oil extraction process.
What Is Castor Oil?
Castor oil is an ingredient obtained after processing the seeds of Ricinus communis. This shrub is a member of the Euphorbiaceae family. It is cultivated in India, China, Brazil, and East Africa. Also called “castor oil”, this vegetable oil has a rather viscous oily texture and is not edible. It is suitable for skin or hair application, allowing it to be adopted in the formulation of skin care, nails, hair, eyelashes, or eyebrows. Castor oil contains fatty acids, including ricinoleic fatty acid or linoleic fatty acid. However, its composition may vary depending on several factors, including growing conditions and the cultivar. Castor oil has nourishing, strengthening, stimulating, healing and soothing properties.
How Is Castor Oil Made?
Castor seeds contain 30-50% oil (m/m). The oil extraction methods from seeds can be mechanical pressing, solvent extraction or a combination of pressing and extraction. At Typology, castor oil is extracted only from the first cold pressing of the seeds; no solvents are used. The castor oil extraction process is as follows:
The beans of Ricinus communis are harvested and cleaned before being dehulled to extract the seeds;
The seeds are crushed and pressed using a screw press. Although this process can be done at low temperatures, mechanical pressing only results in the recovery of about 45% of the oil from castor seeds. Higher temperatures can increase extraction efficiency. Yields of up to 80% of the available oil can be achieved by using high-temperature hydraulic pressing in the extraction process.
In order to separate the oil from the hydrophilic compounds, centrifugations are performed. The result is crude castor oil.
During the refining process, impurities such as colloidal matter, phospholipids, excess free fatty acids (FFA) and coloring agents are removed from the oil. The removal of these impurities ensures that the oil does not deteriorate during prolonged storage. The refining process steps include degassing, neutralization with a strong base such as sodium hydroxide, bleaching, and deodorization.
After these steps of production, castor oil is safe for use in cosmetics. As a matter of fact, it is now rid of a toxic enzyme present in the seeds called ricin. It is this toxin that prevents the use of this plant for food purposes.
Vinay R. Patel & al., Castor Oil: Properties, Uses, and Optimization of Processing Parameters in Commercial Production, Lipid Insights. (2016).