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.

There is a second axis besides the smoke point: the melting point

The table above is where a fat starts to break down. In baking, the temperature at which a fat is still solid decides the result far more often.

• Suet (beef kidney fat) — 45-50°C, more than fifteen degrees above butter. Spotted Dick uses suet because in a 100°C steamer the batter sets first and only then does the fat run out of it. The holes it leaves behind are the crumb. Swap butter in and it melts in the first few minutes, giving a dense pudding instead.
• Butter — around 30°C. In Shortbread the set butter is the structure, which is why it is only scored hot in the tin and lifted out after it cools. Croissant is the other case: the butter has to still be unmelted going into the oven or there are no layers (dough and gluten).
• Milk fat — soft even at fridge temperature. Nanaimo Bar stirs a little butter into its chocolate lid. Pure chocolate splits the moment a knife touches it, and milk fat, staying soft when cold, interrupts that crystal network.
• Vegetable oil — liquid even cold. Which is why Chiffon Cake uses oil rather than butter. A butter cake firms up as its fat sets on cooling; an oil cake stays soft in the fridge.

When the number is not a property of the fat

Every entry above is a figure you look up and then design around. Cocoa butter does not have one. Chocolate Truffles says what it has instead: cocoa butter can set in six crystal forms, and "only one is hard, snaps and shines." Each has its own melting point and its own texture, and which one you get is decided by how you cooled it. Tempering is bringing the melted chocolate down to 31-32°C with seeds of that form still in it; without it the fat sets in unstable forms, converts over the following days and pushes to the surface as white bloom. The failure does not show on the day, which is what separates this from every bullet above — there you choose a fat, here you choose a form, and the same tub of chocolate will give you either.

Nanaimo Bar, two bullets up, is that fat with the decision not taken: nothing is tempered, the lid sets in whatever form it likes, and as that page puts it the crystals "are hard and they cleave" — a lid of pure chocolate splits at the first touch of a knife and takes the middle layer with it. The 30g of butter stirred in is the answer, and it is the milk-fat bullet above being put to work: soft at fridge temperature, it gets in the way of the crystal network instead of joining it. Two fats one layer apart, one of them set on purpose and the other there to stop it setting cleanly.

The question can also be removed rather than answered. A truffle rolled in cocoa needs no tempering at all — "the outside is not chocolate, so crystal form never arises" — and that is the original version of the dish rather than a shortcut.

What the neighbours own: what sugar does has a crystal section of its own, but that one is about size, seeding many at once so no single crystal grows large enough to feel. Here everything is crystalline and the question is which form. And the temperature that decides whether any of it was worth doing is the eater's — cocoa butter begins to melt near body temperature, which is why a long roll between warm palms leaves the surface greasy (serving temperature).

So for frying you read the smoke point, and for baking you read the melting point.

"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).

There is a low end too

This guide is about upper limits throughout, and fat also gets used far colder than any of them. Carnitas submerges pork in lard at 90°C for hours. Smoke points are irrelevant at that temperature: the fat is not a frying medium there but simply a liquid that is not water — not capped at 100°C, and unable to carry water-soluble flavour away (dry heat and moist heat).

Raise the heat in the same pot and the paragraph above applies again from that moment on. What sets the oil temperature is not the oil, it is what you are trying to do.

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.

French Meunière is those few seconds made into a dish. The window is about thirty seconds, and since colour arrives too late to judge by, the cue is the smell. There is also a defined way to stop it: off the heat, pour in cold lemon juice. Cold acid drops the pan temperature at once and arrests the browning where it stands. In that dish the lemon is not acidity, it is the brake.

Finishing oils are not cooking oils

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

Ghanaian Red Red turns that distinction into the structure of a dish. Half the red in its name comes from red palm oil, which is unrefined, low in smoke point and assertive. So the frying is done in a neutral oil and the palm oil goes into the bean stew. One dish, a cooking oil and a finishing oil kept separate — fry in the palm oil instead and you lose the aroma and damage the oil.

• 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.

The exception exists under a condition. Kinpira Gobo does fry in toasted sesame oil from the start — the burdock and carrot are cut into matchsticks, nothing is on the heat for more than ten minutes, and the pan stays below sesame oil's 175°C. Where the time on the heat is short, a finishing oil can be the cooking oil. Break that condition — high heat, or long — and the rule comes back.

The second kind of exception: when the aroma is the thing you want gone

That exception is about time. The other kind is about direction. Ilish Paturi heats mustard oil to smoking in its second step, and its page says plainly that this is "not carelessness, it is the tradition": the oil carries the same allyl isothiocyanate as the seed, and in the oil that pungency is unwelcome, so it is driven off on purpose. One plate keeps the molecule on one side — a cold, water-ground paste sealed in a leaf — and destroys it on the other. Chilli and heat has the molecule; what matters here is the oil.

It is the one case where the first section of this guide reads backwards. Smoke still means the oil is decomposing, and it will still smoke sooner next time — none of that changes. What changes is that the damage is the cost of the step rather than a mistake in it.

Only part of that condition is about the oil

Kinpira Gobo satisfies two separate things at once: nothing is on the heat for more than ten minutes, and the pan stays below sesame oil's 175°C. The paragraph above states them as one condition, and they do not do the same work. The temperature is a limit on the oil — past it the scent goes and bitterness is left in its place, which is damage to the ingredient. The time is a limit on the aroma alone, and it binds only where the aroma is what the bottle was bought for.

Where it is not, a recipe can break the time half deliberately and keep the temperature half. Both of the soups below fry gently in sesame oil and then pour liquid in, which pins the pot near 100°C for everything that follows.

• Hwangtae-guk puts two finishing oils in one pan and rates them by different things. The dried pollock is fried in sesame and perilla oil for two or three minutes before any water goes in, and the soup then simmers for twenty. Its page makes the perilla optional — "without it the aroma is lighter" — and the sesame not: "frying the dry flesh before any liquid goes in is half the colour and half the nuttiness of the broth. Skip the order and you get a bland fish soup." That nuttiness is the fish browning in fat, not the oil's own scent. The negotiable one is the aroma; the one the recipe cannot lose is the fat.
• Miyeokguk calls the same step "the key to a deep broth", then simmers twenty to thirty minutes with the lid on. The scent is long gone by then. What the step leaves behind is the fat, coating the seaweed and carrying the beef's browning out into the broth.

None of this is licence to fry in the good oil. Red Red above is still the shape to reach for wherever the aroma is the purchase, and the olive-oil section's word for the opposite case is the right one: extra-virgin over high heat is not unusable, it is wasted. It is only waste, though, if the aroma is what you were paying for.

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.