Extra virgin olive oil is often promoted as the very best oil to use for cooking.
'If you want quality, never buy anything other than extra virgin olive oil,' says one retailer. 'Extra virgin olive oil is actually one of the healthiest types of oil you can fry with,' says another.
It all depends on how you use the oil, says Gjermund Vogt, senior adviser at Eurofins.
Eurofins laboratories analyse food products and oils on behalf of researchers and the food industry. Vogt himself has studied fats and oils for 30 years.
Other oils are also essentially extra virgin
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Extra virgin olive oil is cold-pressed. The olives are pressed to extract the oil, which is then filtered or centrifuged to remove any remaining fruit particles. The resulting oil is stored in tanks, then bottled and distributed to consumers.
"Extra virgin is the standard quality designation for olive oil established by the International Olive Oil Council. No other vegetable oils have this kind of standardised quality classification, even though rapeseed oil, for example, goes through the exact same process," Vogt tells Science Norway.
Gjermund Vogt has worked with oils for three decades. He recently presented his work at a seminar at the food research institute Nofima.(Photo: Eurofins)
Extra virgin olive oil is often called 'the healthiest of all oils' because it is rich in antioxidants. Whether that is actually true is open to debate, according to Vogt.
"Much of what makes extra virgin oil healthy disappears as soon as you heat it in a frying pan. At that point, the olive oil is no longer extra virgin, and you are left with an oil that is less suitable for frying than oils that are much cheaper," he says.
Add extra virgin at the end
The green colour of extra virgin olive oil comes from its pigments and antioxidants. When the oil is heated, these compounds break down, producing tiny soot particles.
"That can give the food you're frying an unpleasant taste," says Vogt.
Instead, he recommends frying the food in a neutral, refined oil.
"Then you can do what chefs do: drizzle a little extra virgin olive oil over the food at the end for great flavour," says Vogt.
Use olive oil on cold dishes or to add flavour to food after it has been cooked.(Photo: Shutterstock / NTB)
Men burn steaks
Refined oils are designed for cooking at high temperatures. Free fatty acids, pigments, and volatile compounds have been removed so that the oil does not affect the flavour of the food and can tolerate higher temperatures without smoking.
"The oil isn't the problem in the frying pan. Men especially like to cook steak over high heat because they've been taught to sear it on both sides before cooking it further. But if you fry food at too high a temperature, compounds such as acrylamide, PAHs, and cooking mutagens are formed. These increase the risk of conditions such as cancer. But they come from the burnt food, not from the oil," says Vogt.
At normal frying temperatures, he says, this is not a concern.
Oil can also become rancid, and extra virgin olive oil is especially vulnerable. Unsaturated fats react with oxygen in the air, producing substances that create unpleasant tastes and odours.
Astrid Nilsson, a researcher at the food research institute Nofima, believes we have a kind of built-in defence against rancid food because we detect the unpleasant smell and taste very quickly. As a result, we rarely consume large amounts of rancid food, she told Science Norway.
"We can detect the smell even in very small amounts. Either we throw the food away, or our bodies deal with whatever we may end up consuming," says Vogt.
He recommends smelling and tasting the oil before using it and washing the frying pan after use.
"If grease is left in the frying pan and it sits in the cupboard for a week, the oil starts to go rancid. That gives the food an unpleasant taste," says Vogt.
Not all virgin is actually virgin
Vogt notes that not all olive oil sold as extra virgin truly meets the standard.
"Extra virgin olive oil is one of the food products most commonly subject to fraud," he says.
The green colour of extra virgin olive oil comes from chlorophyll in the olives. When the oil is exposed to light, the chlorophyll begins producing oxygen.
"That's why olive oil is sold in brown and green bottles, to prevent light from reaching the oil," says Vogt.
Olive oil gradually loses quality over time. An extra virgin olive oil that has spent a long time in a storage tank in Spain or has been sitting on your kitchen counter for months may deteriorate from extra virgin to virgin, eventually becoming little more than an ordinary olive oil.
Vogt therefore recommends storing olive oil in a cool, dark place – not on the kitchen counter in direct sunlight.
Two years ago, the Norwegian Food Safety Authority inspected olive oils in Norwegian stores. When they analysed the samples, it turned out that 6 out of 19 olive oils were incorrectly labelled as extra virgin, even though they did not meet the standard. In 2024, Italian authorities seized 42 tonnes of counterfeit olive oil that was falsely labelled as being extra virgin, according to CNN.
"That has led to extensive quality control and strict regulations surrounding olive oil," says Gjermund Vogt.
