Cooking Oils: Smoke Point and What Each One Is For

A smoke point marks where the oil starts breaking down

Smoke is not a sign the oil is hot. It is a sign the oil is decomposing — fatty acids splitting off irritants like acrolein, which arrive on the palate as bitterness and a burnt smell.

The part that matters is that it does not reverse. An oil taken past its smoke point has a lower smoke point next time. Which is why oil you scorched once starts smoking sooner when you reuse it.

Rough numbers

Refining and brand move these by 20°C or so, so remember the order and the bands rather than the digits.

• Refined avocado — about 270°C
• Refined olive (pure/pomace) — about 240°C
• Peanut — about 230°C
• Canola, sunflower, grapeseed, refined soy — about 220-230°C
• Extra-virgin olive — about 190-210°C
• Clarified butter (ghee) — about 250°C
• Butter — about 150°C
• Toasted sesame — about 175°C

Those last two are the point of the list. Butter and sesame oil share a table with the others and share almost nothing else.

"Never fry in olive oil" is half true

Refined olive oil has a higher smoke point than canola. Frying in it is fine.

Extra-virgin is the one with the problem: a lower smoke point, and the aromatics you paid for are the first thing high heat destroys. So it is not unusable, it is wasted. That is why aglio e olio and gambas al ajillo use extra-virgin but keep the oil at medium heat or below — in those dishes the oil is the sauce, not the cooking medium.

Deep frying needs 20-30°C of headroom

Frying targets roughly 170-190°C. But the food drops the temperature when it goes in, and turning the heat up to recover creates local spots much hotter than the target.

So you want an oil whose smoke point sits 20-30°C above where you are working: in practice canola, sunflower, peanut, or refined olive. Karaage, tonkatsu, tempura, fish and chips and churros all live in that band (deep frying).

What burns in butter is the milk solids, not the fat

Butter is about 80% fat with water, milk protein and lactose mixed through it. What scorches around 150°C is the solids.

Two ways around it.

• Cut it with oil. Half neutral oil dilutes the solids and they stop catching. This is the standard way to cook French toast.
• Use clarified butter (ghee). With the solids removed it holds to 250°C. Indian cooking like butter chicken uses ghee for that heat tolerance as much as for flavour.

Butter that has gone nut-brown (beurre noisette) is butter moments from burning, and that nutty smell is the Maillard reaction at work. Delicious if you meant it; bitter a few seconds later if you did not.

Finishing oils are not cooking oils

Toasted sesame, extra-virgin olive, chilli oil, truffle oil. What you are buying is aroma, and heat removes it.

• Sesame oil put into a hot pan first loses its scent and leaves bitterness behind. In sigeumchi-namul, kongnamul-muchim and bibimbap it always goes in after the heat is off.
• A dish that seems to want sesame oil for frying almost always wants neutral oil to fry in and sesame oil at the end.

When to throw frying oil away

Used frying oil is not waste, but it is not indefinite either. Cool it, strain through a sieve and paper, seal it, keep it dark.

Three signals say it is finished.

• Darker and thicker than it was — it has polymerised.
• Smoking at a lower temperature than before — the smoke point has dropped.
• It smells cold — that is rancidity.

Oil used for fish carries the fish with it, so do not move it to another job. Scooping out the crumbs as you fry does more for the oil's lifespan than anything else on this list.