Cooking method

Deep frying

Properly deep-fried food is not greasy. Hot oil turns the water at the food's surface to steam, and that steam pushing outwards is what keeps the oil from soaking in — which is why the whole technique comes down to oil temperature.

Why temperature is the whole method

When food goes into hot oil, the moisture just under the surface flashes to steam and rushes outwards. That outward flow is what stops oil flowing inwards, and it is also what dries the surface enough to brown and crisp.

If the oil is too cool, the steam is generated slowly and weakly, oil seeps in, and you get heavy, greasy, pale food. If it is too hot, the surface browns and burns before the inside has cooked, and the oil itself starts to break down and taste acrid.

The right range for most deep frying is roughly 170 to 190°C. Below about 160°C food absorbs oil noticeably; above about 200°C most oils are near or past their limit.

This also explains why crowding the pan is so damaging. Cold food drops the oil temperature, and a lot of cold food drops it a long way — straight into the greasy zone.

Doing it well

• Use a thermometer. This is the one technique where guessing reliably fails, and the difference between 160°C and 180°C is visible in the result.
• Fry in small batches, letting the oil come back up to temperature between them.
• Dry the food or coat it. Wet food spatters violently and cools the oil.
• Use a neutral oil with a high smoke point — rapeseed, sunflower, groundnut. You are using a lot, so cost matters.
• Do not fill the pan more than a third to a half. Oil rises dramatically when food goes in.
• Drain on a rack, not on paper. Paper traps steam underneath and softens the base; a rack lets it escape.
• Salt immediately, while the surface is hot and slightly oily so it sticks.

The double fry

Chips, and several other things, are fried twice at different temperatures, and each fry does a distinct job.

The first fry, at a lower temperature — around 130 to 160°C — cooks the interior through and drives moisture out of the outer layer without browning it. The chips come out pale and floppy, and they can sit for hours or be frozen at this stage.

The second fry, hot — around 180 to 190°C — is brief and does nothing to the interior. It dehydrates and browns the already-dried surface into a hard, glassy shell.

Trying to do both at once is why single-fried chips are either raw in the middle or soggy on the outside: one temperature cannot cook a thick interior gently and blast a surface dry.

Safety, plainly

This is the one domestic technique with a real fire risk, and it is worth being direct about it.

• Never fill the pan more than a third to a half full. Overflow is the commonest cause of a fire.
• Never leave it unattended. Oil goes from hot to smoking to burning quickly.
• Never put wet food into hot oil. Water flashing to steam ejects oil violently.
• If oil catches fire, do not use water. Water sinks, flashes to steam and ejects burning oil. Turn off the heat if you safely can, cover the pan with a lid or a fire blanket, and leave the room and call the fire service if it is not immediately controlled.
• Keep a lid within reach before you start, not in a cupboard.
• Let oil cool completely before moving it. More burns come from carrying hot oil than from frying.

Common questions