The smoke point of olive oil: what actually matters

Smoke point is the temperature at which an oil begins to break down and give off visible smoke. It is the figure most often cited in arguments about cooking with olive oil, and the one most often misunderstood.

The myth worth dropping

You may have heard that extra virgin olive oil "cannot be heated at all". That is not accurate. Extra virgin has a smoke point high enough for nearly all home cooking — sautéing, oven roasting, shallow frying.

Home cooking mostly happens well below that point. Sautéing happens over moderate heat. Oven roasting is normally at a temperature olive oil is perfectly comfortable with. The only places that genuinely exceed it are deep frying and very high-heat wok cooking.

Why smoke point is not the best measure

Smoke point tells you when an oil starts smoking. It does not tell you how well the oil holds up on the way there, and that is the more useful question.

The better measure is oxidative stability — how well an oil resists breaking down when heated. Two things drive it: the balance of unsaturated fats in the oil, and the quantity of natural antioxidants it carries.

Extra virgin olive oil has both. Its polyphenols act as antioxidants, slowing oxidation while it is heated. Refined oils have a higher smoke point but almost no polyphenols, because refining removes them.

This is why a higher smoke point does not automatically mean an oil is better suited to cooking.

What lowers a bottle's smoke point

• High free acidity — the more free fatty acids, the lower the smoke point
• Oil that is old and has already begun to oxidise
• Food particles left in the oil after cooking
• Oil that has been reused several times

Note the first one. Free acidity directly affects smoke point, which means an oil at 0.18% acidity starts from a better place than one at 0.7%, even though both are legally labelled extra virgin.

A practical rule for the kitchen

Forget the number and watch the pan. If the oil is smoking, it is too hot — turn the heat down. If it shimmers and moves easily when you tilt the pan, the temperature is right.

If oil has smoked, do not carry on cooking in it. Oil taken past its smoke point gives food a bitter, scorched taste. Discard it, wipe the pan and start again.

For deep frying, use ordinary cooking oil. Not because extra virgin is unsafe, but because the flavour and polyphenols you paid for are destroyed in the process.