Extra virgin is the top grade of olive oil, and the most expensive to make, which is exactly why it is the grade most often stretched, mislabelled or sold past its best. You cannot test an oil at home the way a laboratory can, but you can learn to read the signs. Here is what to check.
What “extra virgin” actually means
In the EU, extra virgin is a legal grade. The oil must be extracted from olives by mechanical means only, with no chemical refining, and it must pass two kinds of test:
- Laboratory limits on acidity, oxidation and other markers (below).
- A tasting panel: trained tasters must find some fruitiness and no defects such as rancid, musty or vinegary notes.
An oil that fails either test may still be sold, but not as extra virgin. Problems range from outright fraud, such as blending in cheaper refined oil, to the far more common issue of oil that was once extra virgin but has gone stale through age, heat or light.
The lab numbers, explained
These are the main chemical tests for extra virgin olive oil and the limits set by EU rules and the International Olive Council. Lower is better for all of them.
| Test | EU limit for extra virgin | ONLY, 2025 |
|---|---|---|
| Free acidity | ≤ 0.80% | 0.10% |
| Peroxide value | ≤ 20 meq O₂/kg | 7.5 |
| K232 | ≤ 2.50 | 1.37 |
| K270 | ≤ 0.22 | 0.14 |
| ΔK | ≤ 0.01 | < 0.01 |
| Ethyl esters | ≤ 35 mg/kg | 4 |
ONLY figures: 2025 harvest, report O26/27/62, CM Europa S.L., Martos (Jaén), 9 October 2025.
- Free acidity shows how sound the olives were and how quickly they were milled. Damaged or overripe fruit, or olives left waiting, push it up.
- Peroxide value measures early oxidation, the first stage of an oil going stale.
- K232 and K270 are ultraviolet readings. K232 picks up early oxidation; K270 picks up later oxidation and is also sensitive to refined oil.
- ΔK is another ultraviolet check that helps reveal refined oil blended into virgin oil.
- Ethyl esters rise when olives have started to ferment or were poor quality, and can flag oil that has been gently deodorised to hide defects.
Six things to check before you buy
1. A harvest date. Olive oil is a fruit juice, and it is at its best fresh. A best-before date is set by the bottler and doesn’t tell you when the olives were picked; a harvest date or season does.
2. A specific origin. Vague wording such as “blend of EU and non-EU oils” tells you the oil could come from almost anywhere. A named country, region or estate is a better sign, and a single named variety is better still.
3. Dark packaging. Light damages olive oil. Choose a tin or dark glass, and be wary of clear bottles, especially ones that have sat under shop lights.
4. A lab report. Producers with nothing to hide increasingly publish their results. If the numbers are shared, compare them with the limits above.
5. A price that makes sense. Making good extra virgin costs money. A very cheap “extra virgin” isn’t proof of fraud, but it is a reason to look more closely.
6. Your own nose and tongue. Fresh extra virgin smells green or fruity, of grass, tomato, apple or herbs, and is often bitter and peppery. Oil that smells of crayons, putty, wet cardboard or nothing at all is past its best, whatever the label says. (Peppery and bitter is a good sign: see what early harvest olive oil tastes like.)
Myths to ignore
The “fridge test”, the idea that real extra virgin always goes cloudy or solid in the fridge, is not reliable: how an oil behaves in the cold depends on its natural make-up, not just its grade. Colour isn’t a reliable guide either, which is why professional tasters use blue glasses that hide it.
How ONLY shows its work
We publish our lab results. Our 2025 oil was tested by CM Europa S.L. in Martos, Jaén: free acidity 0.10%, peroxide 7.5, K232 1.37, K270 0.14, ΔK below 0.01 and ethyl esters of 4, all well inside the extra virgin limits. 128 pesticides were tested and none were detected. See the details in our lab results section.
The olives are 100% Picual from Jaén, Spain (more in our Picual guide), picked in the first week of October and cold pressed below 27°C, and the oil is EU-certified organic. It is packed in a 500ml pink and gold tin that keeps the light out.