How is castor oil obtained?

Castor oil is an ingredient obtained after processing the seeds of Ricinus communis. This shrub is part of the Euphorbiaceae family. It is cultivated in India, China, Brazil, and East Africa. Also known as "castor oil", this vegetable oil has a fairly viscous oily texture and is not edible. It lends itself to topical or hair application, allowing it to be adopted in the formulation of skincare, nails, hair, eyelashes, or eyebrows. Castor oil contains, among other things, fatty acids, including ricinoleic fatty acid or linoleic fatty acid. However, its composition can vary depending on several factors, including cultivation conditions and the cultivar. In terms of virtues, castor oil has nourishing, strengthening, stimulating, healing, and calming properties.

Castor seeds contain between 30 to 50% oil (m/m). Castor oil can be extracted from the seeds through mechanical pressing, solvent extraction, or a combination of pressing and extraction. At Typology, the castor oil is derived solely from the first cold pressing of the seeds; no solvents are used. The extraction process unfolds as follows:

1. The shells of the Ricinus communis are harvested and cleaned before being shelled to extract the seeds;

2. The seeds are ground and pressed using an endless screw press. Although this process can be carried out at low temperatures, mechanical pressing only results in a recovery of about 45% of the oil from the castor seeds. Higher temperatures can increase the efficiency of the extraction. Yields of up to 80% of the available oil can be achieved using high-temperature hydraulic pressing in the extraction process.

3. In order to separate the oil from the hydrophilic compounds, centrifugations are carried out. We then obtain raw castor oil.

4. During the refining process, impurities such as colloidal matter, phospholipids, excess free fatty acids (FFA) and colouring agents are removed from the oil. The removal of these impurities prevents the oil from deteriorating during prolonged storage. The steps in the refining process include degassing, neutralisation with a strong base such as sodium hydroxide, bleaching, and deodorisation.

Following these stages, castor oil is safe and can be adopted in cosmetology. Indeed, it is rid of a toxic enzyme initially 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).