An edible oil certificate of analysis should cover basic quality, such as free fatty acid, peroxide value, moisture and colour, and identity, such as iodine value or fatty acid profile. It should also include the contaminant tests your market requires for that oil.
Which tests matter most depends on the oil, whether it is refined or cold-pressed, and where you sell it. Limits are set by your spec and your market's law, not by the certificate.
Basic quality tests
- Free fatty acid or acid value: shows how much the oil has broken down. See what FFA level edible oil should have.
- Peroxide value: shows early oxidation, which leads to rancid flavours.
- Anisidine value: shows later-stage oxidation, often requested for refined oils.
- Moisture and volatile matter: water speeds up spoilage.
- Insoluble impurities: dirt, fibre and sediment, especially important for filtered and cold-pressed oils.
- Colour: usually on the Lovibond scale, with red and yellow readings.
- Flavour and odour: a sensory check for off-notes.
Identity and purity tests
These help show that the oil is what it says it is, and not blended with cheaper oils.
- Fatty acid profile by gas chromatography: the most useful single test for identity.
- Iodine value and saponification value: simple checks that each oil falls in its usual range.
- Refractive index and relative density.
- Unsaponifiable matter.
- Specific tests for certain oils, such as the Baudouin test for sesame oil or the Halphen test for cottonseed oil.
Contaminant tests to consider
Your market's rules for these contaminants change from time to time. Check current limits with your national food authority or your food safety adviser.
- Aflatoxins, especially for unrefined groundnut oil.
- Pesticide residues against your market's maximum residue limits.
- Polycyclic aromatic hydrocarbons (PAHs), which can come from smoke or poor drying of seed.
- 3-MCPD and glycidyl esters, which can form during refining at high temperature.
- Mineral oil hydrocarbons, which buyers in some markets now test for.
- Heavy metals such as lead and arsenic.
- Residual solvent, for solvent-extracted oils or where you claim cold-pressed.
- Trans fats, where your market limits them.
Making the certificate useful
A certificate from the supplier's own lab is a useful start, but not proof. For the first orders and at regular intervals, have a sample from the actual batch tested at an independent accredited lab. Check that the certificate names the batch, the date, the method for each test and the units. Our guide to reading a lab certificate explains what to look for.
How we help
We agree the test list with you before the order, draw samples from the batch ourselves and send them to an NABL-accredited lab. You receive the original lab report alongside the supplier's certificate, so differences are easy to spot. Ask for a free sourcing review.