Ricinoleic acid is an 18-carbon fatty acid with one double bond and one hydroxyl group. It makes up about 85 to 90% of the fatty acids in castor oil, and no other common vegetable oil contains it in quantity.
That hydroxyl group is why castor oil is a chemical feedstock and not just an oil. It makes the oil more viscous and more polar, and it gives chemists a reactive site to work with.
How it is sold
Ricinoleic acid is sold as a separate product, made by splitting castor oil with water at high temperature and pressure, or by saponification and acidification. The result is a pale yellow liquid. Commercial grades contain other castor fatty acids, such as oleic, linoleic and stearic acid.
It is used in soaps, textile auxiliaries, metalworking fluids, cosmetics, and as a raw material for esters and estolides. Its salts are used in personal care products.
Why it matters for every derivative
Each castor derivative changes a different part of the ricinoleic acid molecule:
- Hydrogenation saturates the double bond and gives hydrogenated castor oil and 12-HSA.
- Dehydration removes the hydroxyl group and gives dehydrated castor oil, a drying oil.
- Caustic cleavage splits the molecule into sebacic acid and 2-octanol.
- High-temperature cracking splits it into undecylenic acid and heptaldehyde.
- Air blowing links molecules together and gives blown castor oil.
Feedstock and what to check
This is why the ricinoleic acid content of the starting oil matters. Lower content means lower yields and more by-products. When you buy a derivative, it is fair to ask what castor oil grade the plant uses.
For ricinoleic acid itself, ask for acid value, hydroxyl value, iodine value, colour and moisture, and a fatty acid profile by gas chromatography. A low acid value can mean the oil was not fully split. Check the certificate against your own lab results, as set out in reading a lab certificate.
Castor oil grades as feedstock
Indian castor oil is traded in several grades. First special grade (FSG) is the most common commercial grade, with low colour and low free fatty acid. Commercial grade is darker and less refined. Pale pressed and other refined grades serve cosmetic and specialty uses.
The grade affects the derivative. A plant that starts from a darker, higher-acid oil can still make an acceptable product, but it needs more refining and loses more yield. Colour problems in finished derivatives often trace back to the oil.
If colour or odour matters to you, ask the plant to name its feedstock grade and to show certificates for the oil as well as the derivative. Our overview of castor oil derivatives made in Gujarat shows where ricinoleic acid sits in the wider product range.
Next step
We find plants that make ricinoleic acid and other castor derivatives, test samples and check each lot. Book a free sourcing review to start.