Olive oil

What the grades mean

• Extra virgin — the first pressing, mechanical only. It has aroma, and the bitterness and pepperiness of polyphenols. Smoke point about 190–210°C.
• "Pure" or plain olive oil — blended with refined oil. Little aroma, higher smoke point (around 230°C).

The practical rule: extra virgin where the flavour is part of the dish, plain olive oil or a neutral oil where you just need fat.

Can you cook with it?

Yes. Sautéing and frying in a pan generally stay under 180°C, inside extra virgin's smoke point. Aglio e Olio and Gambas al Ajillo are dishes built on heating olive oil.

Deep frying is the exception — it runs above 190°C and reuses the oil. Use a high smoke point oil for that (see Deep frying).

Raw is where it really earns its price

• Salad dressings, Caprese.
• Poured over a finished dish — Hummus, soups, roasted vegetables.
• With bread, Bruschetta.

This is where a good oil is unmistakable. Fresh oil catches slightly at the back of the throat; that is the polyphenols, and a sign of freshness.

It is an emulsion ingredient

A dressing splitting and a pasta sauce going glossy are the same phenomenon. Something has to bind water and oil; in pasta, the starch in the cooking water does it — see Why sauces split.

Storing

Light, heat and air are the enemies.

• Buy it in dark glass or a tin, and do not keep it beside the hob.
• Use it within two or three months of opening. Oxidised oil smells faintly of crayons.
• Refrigeration makes it cloudy and semi-solid but does no harm; it clears again at room temperature.

Substitutes

• Canola or sunflower — when you want no flavour, and for deep frying.
• Sesame oil — not a substitute; it makes a different dish.
• Butter — possible for sautéing, but a much lower smoke point.