K232 and K270 are indices obtained by ultraviolet spectrophotometric analysis. They help assess oxidation-related changes in olive oil and are among the official parameters used for classification. They are not home tests: correct measurement requires a defined analytical method, suitable equipment and a competent laboratory.
In brief
- K232 measures UV absorption around 232 nm and is mainly associated with primary oxidation products.
- K270 (or K268, depending on the method) concerns a UV region associated with compounds that can increase with more advanced oxidation and refining.
- For extra virgin olive oil, EU rules set specific limits together with ΔK and other parameters.
- No single value proves overall quality, freshness or authenticity.
What are K232 and K270?
Oils absorb ultraviolet radiation differently depending on the molecules present. The official method measures specific extinction at defined wavelengths. These are instrumental measurements, not visual or sensory judgements.
What K232 indicates
Absorption near 232 nm is mainly linked to conjugated dienes that can form during early lipid oxidation. A high result may therefore be consistent with oxidative change, but must be read with other analytical results and the sample history.
What K270 indicates
Absorption around 268–270 nm is associated, among other things, with conjugated systems that may increase during more advanced oxidation and in refined oils. It should not be interpreted alone.
EU limits for extra virgin olive oil
For the extra virgin category, EU reference limits include K232 ≤ 2.50, K268 or K270 ≤ 0.22 and ΔK ≤ 0.01. Classification nevertheless depends on compliance with the full set of applicable characteristics.
| Parameter | EU EVOO limit | What it helps assess |
|---|---|---|
| K232 | ≤ 2.50 | Mainly primary oxidation phenomena |
| K268/K270 | ≤ 0.22 | UV absorption linked also to advanced oxidation and refining |
| ΔK | ≤ 0.01 | Shape/anomalies of the UV spectrum |
Do K232 and K270 tell you whether an oil is “good”?
Not by themselves. They are important pieces of chemical control, while extra virgin classification depends on several chemical parameters and the required organoleptic assessment.
Can you check them at home?
No. Colour, clarity, thickness, refrigeration behaviour or taste cannot provide K232 or K270. The method requires UV spectrophotometry under defined conditions. Consumers can check the label, package integrity, best-before date and storage, but these do not replace official analysis.
How to read an analysis certificate
- Check that the sample and lot are identified.
- Check the analytical method and date.
- Read K232, K270/K268 and ΔK together.
- Compare them with limits for the declared category.
- Consider the other classification parameters too.
FAQ
Does a high K232 mean the oil is fake?
No. An out-of-limit result indicates non-compliance for that parameter/category but does not by itself identify the cause or prove fraud.
Does a low K270 guarantee extra virgin status?
No. The oil must meet the complete set of applicable requirements.
Are peroxide value and K232 the same?
No. They are different, complementary analyses.
Can K270 reveal refined oil?
It can contribute to analytical interpretation because refining can affect UV absorption, but authenticity and classification cannot be established from K270 alone.
Conclusion
K232, K270/K268 and ΔK help read part of an oil’s chemical history. No home shortcut replaces these laboratory parameters, and no single value describes quality and authenticity on its own.