A Cook's Guide to Cooking Oils and Fats

Most kitchens end up with a graveyard of half-used bottles: a tired olive oil gone slightly fishy, a vegetable oil nobody can date, a block of butter with a fridge tang. You don't need fifteen fats. You need three or four you understand, and a clear idea of which job each one does. This guide sorts that out.

Smoke point, and why it matters less than you think

The smoke point is the temperature at which a fat starts to break down, throw off acrid smoke, and taste bitter. For frying and high-heat roasting you want a fat that comfortably clears the temperature you're cooking at, with room to spare.

Rough numbers worth remembering:

• Refined vegetable, sunflower, rapeseed (canola) and groundnut oils sit around 220 to 230C. Good for deep-frying and searing.
• Light or refined olive oil lands near 200C.
• Extra virgin olive oil is lower and more variable, often 180 to 190C for a decent bottle.
• Butter starts smoking around 150C because of its milk solids. Clarified butter or ghee, with those solids removed, climbs to roughly 230C.

Here's the part people miss: smoke point is not a fixed property carved into the bottle. It drops every time you heat the oil, because each use leaves behind broken-down compounds and stray food particles that scorch on the next round. A fresh oil and a tired one with the same label behave very differently. So the practical rule is to match the fat to the heat, and to bin oil that smokes far sooner than it should.

The everyday lineup

If I had to keep four fats, it would be these.

A neutral oil for heat. Rapeseed or sunflower for searing, roasting potatoes, and frying. Cheap, high smoke point, no flavour of its own to fight the food. This is what carries a fast wok dish like a Beef and Broccoli Stir-Fry, where you want the pan screaming hot and the oil staying out of the way.

Extra virgin olive oil for flavour. Treat the good bottle as a seasoning, not a cooking medium. Drizzle it raw over soup, toss it through a salad, finish a plate of beans. A dish like Fasoliyyeh Bi Z-Zayt (Syrian Green Beans with Olive Oil) leans on the oil's fruitiness, so a flat supermarket bottle will show. You can absolutely cook with olive oil too, despite the old myth that heat ruins it; gentle frying is fine. Just keep the prized stuff for where you can taste it.

Butter for browning and richness. Nothing else gives that nutty depth or the same flavour in a sauce. The catch is the milk solids burn quickly, which is why butter in a hot pan goes from foaming to brown to black in under a minute.

A frying oil you're willing to reuse. Groundnut (peanut) or sunflower, in enough quantity to deep-fry properly.

Butter without burning it

Two fixes. The simple one: add a splash of neutral oil to the pan alongside the butter. The oil raises the effective working temperature and buys you time, which is handy when you're shallow-frying something that needs colour.

The better one for high heat: clarify it. Melt butter gently, let the white milk solids settle and the foam rise, then spoon off the foam and pour the clear golden fat off the milky sediment at the bottom. What you're left with keeps for weeks and takes real heat. This is the same principle behind ghee, and behind cooking meat slowly in its own fat, as with Duck Confit, where the gentle fat does the work and nothing scorches.

Deep-frying: get the temperature right

The single biggest frying mistake is oil that's too cool. Food dropped into lukewarm oil sits there absorbing it, and you get a greasy, pale, heavy result instead of a crisp shell. Most things fry well between 170 and 190C.

• Use a thermometer if you have one. If not, a cube of bread should turn golden in about 40 seconds at the right heat.
• Fry in small batches. A big pile of cold food crashes the temperature and everything steams.
• Dry the surface of whatever you're frying. Wet food spits violently and cools the oil.

This is exactly why a coating recipe like Chicken Karaage tells you to rest the floured pieces and bring the oil back up between batches, and why Churros go soggy if the oil dips. Strain cooled frying oil through a sieve and store it in a dark jar; you can reuse it a few times until it darkens, smells off, or gets foamy.

Storage, and how to spot a fat that's turned

Oils go rancid through light, heat and air. Rancid oil smells like old crayons, putty or cardboard, and it tastes faintly bitter at the back of the throat. Once a fat is there, no cooking will rescue it.

• Keep oils in a cool, dark cupboard, not on a sunny windowsill or next to the hob.
• Buy olive oil in dark glass or tins, and buy a size you'll finish within a few months.
• Cap bottles tightly; air is the enemy.
• Nut and seed oils with delicate flavour, such as walnut or toasted sesame, turn fastest. Keep those in the fridge.

A cold, slightly cloudy olive oil from the fridge is fine; it clears as it warms. That isn't a fault. Rancidity is about smell, not appearance.

A few quick pairings

For a sear or a roast, neutral oil. For garlic gently sizzled to sweet, soft and golden, olive oil, as in Gambas al ajillo, where the oil becomes part of the sauce. For pastry and baking, butter for flavour or a neutral oil where you want a tender, plain crumb. Keep the bottles few, keep them fresh, and match the fat to the heat. That covers almost everything you'll cook.