The peroxide value is one of the chemical parameters used to assess olive oil quality. It does not measure acidity and, by itself, cannot tell whether an oil tastes good: it mainly reflects products formed during the primary stage of oxidation.
- EU rules set a maximum peroxide value of 20.0 mEq O₂/kg for extra virgin olive oil.
- Being below this limit does not by itself prove that an oil is extra virgin: the other legal chemical and sensory criteria must also be met.
- Consumers cannot measure it reliably at home; an official laboratory analysis is required.
- Light, oxygen, heat and time can promote oxidation during storage.
What is peroxide value?
When lipids react with oxygen, hydroperoxides form in the early stages. Peroxide value is an analytical index of these primary oxidation products, expressed as milliequivalents of active oxygen per kilogram of oil.
What is the limit for extra virgin olive oil?
EU Delegated Regulation 2022/2104 sets a maximum of 20.0 mEq O₂/kg for extra virgin olive oil. The same legal table also includes free acidity, K232, K268/K270, ΔK, fatty-acid ethyl esters and sensory requirements, so classification depends on a set of criteria rather than one number.
Are peroxide value and acidity the same?
No. Free acidity concerns free fatty acids; peroxide value concerns primary oxidation. A low acidity therefore does not make oxidation indicators unnecessary.
Does a lower value always mean better oil?
No. A low peroxide value is compatible with limited primary oxidation, but it is not a universal quality score. Peroxides are intermediates and other indicators, including UV absorbance, help describe later stages of deterioration.
What happens during storage?
Long-term storage studies show that peroxide value can rise over time and that temperature and variety influence oxidation. In one study of four varieties stored for up to three years, some samples kept at 20 °C eventually exceeded the EVOO peroxide limit while oxidative stability declined.
What can consumers check at home?
Consumers can limit deterioration by keeping oil tightly closed, away from light and heat and avoiding unnecessary exposure to air. You cannot determine peroxide value from colour, smell or improvised home tests. A quantitative value requires laboratory analysis.
How to read an analysis certificate
| Item | What it indicates | At home? |
|---|---|---|
| Peroxide value | Primary oxidation | No, laboratory |
| Free acidity | Free fatty acids | No, laboratory |
| K232 / K268-K270 | UV oxidation indicators | No, laboratory |
| Defects / fruitiness | Official sensory profile | Official classification requires a recognised panel |
FAQ
What should the peroxide value of EVOO be?
In the EU, extra virgin olive oil must be at or below 20.0 mEq O₂/kg and also meet all other applicable requirements.
Can I detect peroxide value by taste?
No. Tasting may reveal sensory defects but does not provide the analytical peroxide value.
Is lower always better?
Not as an overall judgement. It is important, but quality and classification require the chemical and sensory indicators to be considered together.
Does peroxide value rise over time?
It can rise during primary oxidation, but not indefinitely because peroxides can later decompose into secondary products. This is why several indicators are used.
Conclusion
Peroxide value describes one specific part of an oil’s condition: primary oxidation. It should never be treated as an absolute quality score.