Castor seed is not sold in a long ladder of named grades like cumin or sesame. It is mostly traded as one commercial quality, and the price is adjusted for oil content, moisture and admixture against an agreed basis.
That makes the contract terms the real grade. Two lots both called castor seed can be worth different amounts once oil and foreign matter are measured.
Why castor is graded differently
Castor seed is not a food. It contains ricin, a toxic protein, and almost all of it is crushed for castor oil, which goes into lubricants, coatings, cosmetics, polymers and chemical derivatives. The crusher cares about how much oil the seed yields and how clean it is, not about appearance.
Gujarat grows the large majority of India's castor, and India is the world's main source of castor seed and castor oil. Most seed is crushed inside India, so the export trade is mainly in oil and derivatives. Whole seed exports are smaller and usually go to crushers abroad.
What actually separates one lot from another
- Oil content: the main value driver, measured in a lab and usually expressed on a stated moisture basis.
- Moisture: wet seed weighs more, yields less oil and stores badly.
- Admixture and foreign matter: stalks, husk, stones, dust and other seeds that add weight but no oil.
- Damaged, shrivelled and immature seed: lower oil and often higher free fatty acids in the crushed oil.
- Seed size and uniformity: sometimes noted, but rarely the basis of price.
Terms you will hear
Traders talk about a basis quality: a stated oil content, moisture and admixture that the price assumes. If a delivered lot tests above or below that basis, the price moves up or down by an agreed scale. Lots far outside the basis can be rejected.
Castor seed has also traded as a futures contract on NCDEX, and the exchange contract sets its own basis quality and tolerances. Physical traders often quote with reference to that. How futures link to physical contracts is explained in what an oilseed futures market is.
You may also see seed described by cleaning level, such as machine-cleaned, or by crop year. New-crop seed from the main harvest, roughly late winter to spring in Gujarat, is usually preferred to old stock.
What to put in your contract
- The basis oil content and the moisture basis it is expressed on.
- The test method for oil and the lab that will run it.
- Maximum moisture, admixture and damaged seed, with the price scale for each.
- The rejection limit beyond which you may refuse the lot.
- Who draws the sample, when, and how many sealed counter-samples are kept.
- Packing, usually PP or jute bags, and the crop year.
Handling and safety points
Because castor seed is toxic, it must never be mixed with food or feed products in a store or a container. Ask the supplier how they keep castor separate, and check the container is clean before and after use.
Castor meal, the solid left after crushing, is also toxic unless properly treated, and it is mostly used as an organic fertiliser. If you are buying meal, treat it as a separate product with its own spec. For oil content targets on seed, see what oil content castor seed should have.
How we help
We find castor seed suppliers in Gujarat who can deliver against a written basis, and we agree the oil test method and price scale before you sign. We draw and seal samples at loading and have them tested at an NABL-accredited lab. Ask for a free sourcing review.