What is a good peroxide value for olive oil?

Extra virgin olive oil must measure 20 meq O₂/kg or less under EU, UK and IOC rules. A fresh oil that has been kept away from light and air usually measures under 10. Among extra virgin oils, a single-digit figure is a good sign of freshness, but check it alongside K232, K270, acidity, the harvest year and how the oil tastes.

Is a high peroxide value bad?

A high peroxide value means the oil has started to oxidise through exposure to oxygen, light or heat. Above 20 meq O₂/kg the oil can no longer be sold as extra virgin or virgin, whatever the label says. As oxidation continues, the oil loses its fresh fruitiness and develops a rancid smell of stale nuts or old crayons.

Is a lower peroxide value always better?

Not on its own. Refined olive oil has a legal peroxide limit of 5, stricter than extra virgin's 20, because refining breaks peroxides down. Peroxide can also peak and then fall in oil stored under light, so an old bottle may show a low reading. A low figure means most when K232, K270 and the tasting are also clean.

Does peroxide value increase over time?

Usually, but not in a straight line. Peroxides turn into secondary compounds such as aldehydes, so the value can peak and then drop. In one study, oil stored under light peaked in the second or third month and oil kept in the dark in the sixth. In another, a tinned oil stored in the dark for six years never passed 20, but its UV values did.

Can you test peroxide value at home?

Not reliably. Peroxide value is measured in a lab by titration: the oil is dissolved, potassium iodide is added and the released iodine is measured. At home, the best you can do is smell and taste. If the oil smells like stale walnuts or old crayons, oxidation is already advanced; the early stage shows up only in analysis.

Reading the label #11

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30 October 2026 · 3 min read

Olive Oil Peroxide Value: What It Means and What Number to Look For

Quick Answer

Peroxide value measures the first stage of oxidation in olive oil, in milliequivalents of active oxygen per kilogram (meq O₂/kg). Extra virgin oil must stay at or below 20 under EU, UK and International Olive Council rules. Fresh, well-kept oils usually measure under 10, but a low figure means little without K232, K270 and taste.

Peroxide value tells you how far an olive oil has started to oxidise. It counts the hydroperoxides that form when fat meets oxygen, in milliequivalents of active oxygen per kilogram (meq O₂/kg). Extra virgin oil must measure 20 or less under EU, UK and International Olive Council (IOC) rules, and fresh oil kept from light usually sits below 10. But the number only captures the first step of ageing, so read it with the UV values K232 and K270 and with your own nose.

What the number actually measures

When oil is exposed to oxygen, light or heat, its fatty acids pick up oxygen and form hydroperoxides. These are the primary oxidation products: they have no smell yet, but they are the raw material of rancidity. In the lab, the oil is dissolved in an acetic acid solvent, potassium iodide is added, and the iodine released is titrated. Where acidity records how the olives were handled before pressing, peroxide records what the oil has been through since: malaxation, tank storage, the bottle and the shelf.

The limits, and the surprising row

Annex I of EU Regulation 2022/2104 sets the quality limits; the UK's retained version of Regulation 2568/91 uses the same figures:

Extra virgin: peroxide ≤20 · K232 ≤2.50 · K270 ≤0.22 · ΔK ≤0.01
Virgin: peroxide ≤20 · K232 ≤2.60 · K270 ≤0.25
Olive oil (refined + virgin blend): peroxide ≤15
Refined olive oil: peroxide ≤5

Refined oil gets the strictest limit because bleaching and deodorising break peroxides down. So a very low value is not proof of a great oil, and some lab blogs that call "under 5" the mark of quality are describing what refining also achieves. Watch the unit too: some papers report mmol O₂/kg, which is half the meq figure, so "10 mmol" equals the 20 meq limit.

Myth: peroxide only ever goes up

Hydroperoxides are intermediates. Over time they break into aldehydes and ketones, the compounds you smell as stale walnuts or old crayons, and the peroxide value can peak and then fall. Vekiari and colleagues (Grasas y Aceites, 2007) found that extra virgin oil under daylight or artificial light peaked in the second or third month and then declined, while oil kept in the dark peaked in the sixth month. A bottle that has sat in a bright shop window can look clean on peroxide precisely because it is past the peak. K270, which tracks the secondary products, and a tasting will catch it.

The opposite case is just as telling. Macciola and De Leonardis (OCL, 2022) stored Coratina extra virgin oil in tins, in the dark at room temperature, for six years. Peroxide rose steadily but never passed 20; K270 exceeded the limit after four years and K232 after five. The oil lost its grade on UV values, not on peroxide.

What a label figure means

Under Article 10(d) of Regulation 2022/2104, a label may state acidity only if peroxide, wax and UV values appear beside it in the same size, and each must be the maximum expected by the best-before date, not the reading on bottling day. A lone peroxide or acidity claim is therefore incomplete. Our guide to telling real olive oil from the rest covers what else to check.

Our lot values

Our 2025 lots measured peroxide 7.4 (lot 2025-EH-03, Memecik picked green in October) and 8.9 (lot 2025-EH-05, November). These are readings at analysis, not best-before maxima; our bottling target is 10 or below, half the legal limit, which is why the oil waits in tanks shielded from light and oxygen. Values for the 2026–27 harvest will be published in the lot register once analysed. The October lot is bottled as Ultra Premium 500 ml, where you can see all four values together; the wider range is in our olive oil collection, and our extra virgin explainer covers the tasting panel side.

Frequently Asked Questions

What is a good peroxide value for olive oil?: Extra virgin olive oil must measure 20 meq O₂/kg or less under EU, UK and IOC rules. A fresh oil that has been kept away from light and air usually measures under 10. Among extra virgin oils, a single-digit figure is a good sign of freshness, but check it alongside K232, K270, acidity, the harvest year and how the oil tastes.
Is a high peroxide value bad?: A high peroxide value means the oil has started to oxidise through exposure to oxygen, light or heat. Above 20 meq O₂/kg the oil can no longer be sold as extra virgin or virgin, whatever the label says. As oxidation continues, the oil loses its fresh fruitiness and develops a rancid smell of stale nuts or old crayons.
Is a lower peroxide value always better?: Not on its own. Refined olive oil has a legal peroxide limit of 5, stricter than extra virgin's 20, because refining breaks peroxides down. Peroxide can also peak and then fall in oil stored under light, so an old bottle may show a low reading. A low figure means most when K232, K270 and the tasting are also clean.
Does peroxide value increase over time?: Usually, but not in a straight line. Peroxides turn into secondary compounds such as aldehydes, so the value can peak and then drop. In one study, oil stored under light peaked in the second or third month and oil kept in the dark in the sixth. In another, a tinned oil stored in the dark for six years never passed 20, but its UV values did.
Can you test peroxide value at home?: Not reliably. Peroxide value is measured in a lab by titration: the oil is dissolved, potassium iodide is added and the released iodine is measured. At home, the best you can do is smell and taste. If the oil smells like stale walnuts or old crayons, oxidation is already advanced; the early stage shows up only in analysis.

Sources

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