How to Store Olive Oil | Oikos Antalis

Once bottled, an extra virgin olive oil remains sensitive to three factors: light, oxygen and heat. Yet the choice of bottle and a few simple habits at home are enough to preserve its aromas and polyphenols for much longer. Here is what the studies and institutions say, and what to take from them in practice.

Why light, air and heat damage the oil

Light, enemy number one

For the International Olive Council (IOC), light is the main threat to olive oil quality. The explanation lies partly in the oil's green pigments: according to a study published in Foods in 2023, chlorophylls and their derivatives, pheophytins, act as photosensitisers. When exposed to light, they accelerate the oxidation of the oil by producing singlet oxygen. Older work published in the Journal of the American Oil Chemists' Society also shows that the stronger the light intensity, the more peroxides form, and that polyphenols are mainly affected by light.

A 2019 Japanese study illustrates this well: after five weeks in the sun, the oil kept in a clear glass bottle was the most degraded, with fewer pigments and phenolic compounds. The same bottle wrapped in aluminium showed no degradation, and amber glass limited the damage without preventing it entirely.

Oxygen, especially after opening

The IOC points out that contact with oxygen accelerates oxidation. Before opening, the container must be airtight; after opening, the air space above the oil should be kept to a minimum. A study published in Food Packaging and Shelf Life in 2019 thus links the faster degradation of oil in tins to the oxygen in the headspace, which grows each time oil is poured out.

Heat, close behind

The IOC ranks heat as the second threat and recommends storing oil between 13 and 25 °C. The UC Davis Olive Center states that extra virgin oil keeps longer at 15 °C than at 25 °C. In a study published in Food Control in 2010, light, a temperature of 35 °C and a large headspace all degraded the quality of the oil over the months.

Clear or opaque bottle: how do the containers compare?

Clear glass: the least protective against light. A study published in Molecules in 2022 found that oil in a clear container degrades the fastest and recommends non-transparent containers.
Dark glass: it filters out some of the light and is among the materials recommended by the IOC, along with ceramic and food-grade stainless steel. It is not, however, a substitute for storage away from light.
Metal tin: completely opaque. The Molecules study considers it the most suitable against photo-oxidation, and a Food Control study (2007) ranks tinplate among the best packaging. The IOC, on the other hand, advises against iron containers, which promote oxidation.
PET plastic: in the 2010 study, glass offered better protection than PET. A 2013 study under shop-type lighting shows that the colour of the PET bottle makes a clear difference to the level of protection.
Bag-in-box and multilayer packaging: in the 2019 study, nitrogen-filled pouches left little headspace, and the oil stayed in the extra virgin category longer than in tins. A Food Chemistry study (2021) covering ten months of light exposure also gives the advantage to an aluminium-lined multilayer carton over green glass.

The UC Davis Olive Center adds a caveat, however: protective packaging alone does not guarantee the quality of the oil it contains. The 2021 study also shows that the oil's initial antioxidant content matters as much as the packaging.

In the shop: shelf lighting matters too

The IOC points out that preserving the oil, from the production chain to the point of sale, is the responsibility of the producer, the distributor and the retailer. The 2013 study mentioned above simulated precisely the fluorescent lighting of a shop: polyphenols, chlorophyll and carotenoids were the indicators most sensitive to this exposure. On the shelf, it is therefore best to choose a non-transparent container, as recommended by the authors of the 2022 study.

At home: dos and don'ts

Do

Store the oil in a dark place, between 13 and 25 °C, as recommended by the IOC.
Cover a clear bottle with an opaque wrapping, for example aluminium foil.
Close the cap after each use and decant a large quantity into small bottles made of dark glass, ceramic or stainless steel, to limit air. Our oil bottles are designed for this.
Buy sizes that match one to three months of use, and no more than you will use in a year.
Use the oil within one to three months of opening.

Don't

Leave the bottle next to the cooker, a radiator or on a windowsill: the IOC specifically cites these sources of heat and light.
Store it near paints, detergents or cooking fumes: oil absorbs odours.
Use an iron container.

Best-before date or harvest date?

The wording "best before" is a date of minimum durability. According to the DGCCRF (the French consumer protection authority), it indicates how long the food retains its qualities; it is not mandatory in the way a use-by date is. After this date, a product whose packaging is intact can be consumed safely, but it may have lost some of its qualities, such as its aromas.

The harvest date is a better guide to freshness, but it is regulated. Delegated Regulation (EU) 2022/2104 only allows the harvest year to be stated if 100% of the contents of the container come from that harvest, in the form of the marketing year or the month and year of harvest. The same text requires the label to state that the oil must be stored away from light and heat. To decode the rest of the information, see our guide on how to read an olive oil label.

What Oikos Antalis does

At Oikos Antalis, we publish the laboratory analyses of each of our oils, harvest after harvest, on our Analyses page. To better understand these light-sensitive compounds, also read our article on olive oil polyphenols.

FAQ

Can olive oil be kept in the fridge?

Yes. According to the IOC, cold storage at around 4 °C can help prevent oxidation. The oil may then turn cloudy or partly solidify: this is a reversible phenomenon that does not affect its quality. The IOC notes, however, that for an unfiltered oil, cold can increase suspended particles and reduce the polyphenol content.

My oil is cloudy: has it gone off?

Not necessarily. The UC Davis Olive Center states that cloudiness or sediment does not mean the oil has spoiled. To assess an oil, our article on olive oil defects helps you spot a rancid oil.

How long can an opened bottle be kept?

The IOC advises using it as quickly as possible, ideally within one to three months of opening.

Is dark glass enough?

It protects better than clear glass, but a 2019 study showed that an oil in amber glass exposed to the sun still developed oxidation products. So always store the bottle away from light.

Clear or opaque bottle: how to store your olive oil properly