Chips. A croquette. Vegetable tempura. Nothing is as recognisably crisp as something fresh from the fryer. The technique behind it is simpler than the result suggests, but the details make the difference between golden brown and greasy.

Deep-frying is completely submerging food in hot oil or fat, usually at 170 to 180 °C. Because of the high temperature the moisture on the outside evaporates immediately. That forms a crisp crust while the inside stays soft.

What is deep-frying?

When deep-frying, the food lies completely in the oil. The heat comes from all sides at once, so it cooks quickly and evenly.

You need:

a deep fryer or a heavy, deep pan;
a neutral oil or fat with a high smoke point;
a thermometer, or a fryer with a thermostat;
a slotted spoon or frying basket and a rack with kitchen paper.

Why does it work?

When food goes into hot oil, the water on the outside evaporates with a lot of steam. That steam holds back the oil for a moment. If the oil is hot enough, the outside quickly becomes dry and crisp. If the oil is too cold, the food soaks up fat and turns heavy.

Hot enough is crisp, too cold is greasy.

How to deep-fry well

Step 1 – Choose the oil

Use a neutral oil that can handle high temperatures, such as sunflower oil, groundnut oil or special frying fat. Extra virgin olive oil is less suitable for this.

Step 2 – Don’t fill the pan too full

Fill a pan to no more than half. Oil foams up when food goes in and can otherwise boil over.

Step 3 – Heat the oil to the right temperature

Heat to about 170 to 180 °C and check with a thermometer. Without a thermometer: drop in a piece of bread. It should turn golden brown in about 30 seconds.

Step 4 – Pat the food dry

Water and hot oil are a dangerous combination: it spits. Pat the food thoroughly dry before it goes into the pan.

Step 5 – Fry in small batches

Too much food at once makes the temperature drop sharply. Fry in batches and let the oil return to temperature in between.

Step 6 – Drain and salt straight away

Lift the food out of the oil and let it drain on a rack or kitchen paper. Salt straight away, while it is still hot, because then the salt sticks.

The secret is in frying twice

For crisp chips you fry twice. The first time, at about 150 to 160 °C, makes the potato soft inside. Then let it rest for a moment. The second time, at 175 to 180 °C, makes the outside crisp and golden to light brown. Don’t fry dark brown: heavily browned potato products contain more acrylamide, a substance you are better off limiting.

First make it soft, then make it crisp.

What do you fry for how long?

Ingredient	Temperature	Guide time
Chips, first time	150 to 160 °C	5 to 6 minutes, still pale
Chips, second time	180 °C	2 to 3 minutes, golden brown
Croquettes and bitterballen	180 °C	3 to 5 minutes
Vegetables in batter (tempura)	170 to 180 °C	2 to 3 minutes
Fish in batter	180 °C	4 to 6 minutes
Chicken nuggets	175 °C	4 to 5 minutes, centre 75 °C

These are guide times. The thickness of the food determines the exact time, so always check.

Deep-frying safely

Hot oil is dangerous. So watch out for:

never leave the pan unattended;
always pat food dry, especially ice or frozen food;
don’t use water to put out an oil fire: put a lid or fire blanket on the pan and turn off the heat;
don’t heat the oil above about 190 °C;
keep children away.

What do you do with the oil?

You can use frying oil several times. Let it cool, strain it through a fine sieve or coffee filter and keep it in a closed jar in a cool, dark place. Replace the oil when it is dark, foams, smokes or gets a sharp smell.

Never pour old frying oil down the sink. Take it to your local council or collection point.

Which oil do you choose?

Oil or fat	Approx. smoke point	Note
Sunflower oil (refined)	about 220 °C	neutral, widely used
Groundnut oil	about 230 °C	neutral, high heat
Frying fat	about 200 °C	gives a typical chip flavour
Olive oil (extra virgin)	about 190 to 210 °C	less suitable, expensive and with its own flavour

The values are indicative. An oil that smokes is too hot and should be replaced.

Making chips: the right potato

Choose a floury potato with a lot of starch, such as Bintje. It becomes airy inside and crisp outside. Waxy potatoes give a denser chip. Rinse the sticks to remove the surface starch and pat them very dry.

Batter and breadcrumbs

Batter

For tempura you mix flour with ice-cold water into a light, lumpy batter. Don’t stir too long, because then it turns tough. Dip the vegetables or fish through it and let the excess drip off.

Breadcrumbs

First coat the food in flour, then in beaten egg and finally in breadcrumbs. Press the breadcrumbs on firmly and let the coating rest for a moment so it stays on.

Deep fryer or ordinary pan?

A deep fryer with a thermostat keeps the temperature constant and is safer. You can also deep-fry in an ordinary heavy pan, but then you need a thermometer and have to pay more attention.

The most common mistakes

The oil is too cold

The food soaks up fat and becomes heavy and greasy.

Solution: use a thermometer and wait until the oil is 170 to 180 °C.

The oil is too hot

The outside burns while the middle is raw.

Solution: keep the temperature below 190 °C.

You fry too much at once

The temperature drops and the crust turns limp.

Solution: fry in batches.

The food is wet

It spits and the crust doesn’t get crisp.

Solution: pat it thoroughly dry.

You don’t let it drain

It stays greasy and soft.

Solution: let it drain on a rack.

Practise with fresh chips

Cut potatoes into sticks of about 1 cm, see batonnet.
Rinse them, soak them in cold water for 30 minutes and pat them very dry.
Fry them for 5 to 6 minutes at 160 °C, still pale.
Let them rest for 10 minutes and heat the oil to 180 °C.
Fry them for 2 to 3 minutes until golden brown, drain and salt straight away.

That way you taste the difference between chips fried once and chips fried twice.

Making tempura: step by step

Cut vegetables into thin slices or sticks, such as carrot, pepper, courgette and sweet potato, and pat them dry.
Beat 1 egg with 200 ml of ice-cold water. Add 120 g of flour and stir briefly, the batter may stay lumpy.
Heat the oil to 170 to 180 °C.
Dip the vegetables through the batter and let the excess drip off.
Fry in small batches for 2 to 3 minutes until the batter is light golden.
Drain on a rack and serve straight away with a dipping sauce of soy sauce and a little lime.

The secret of light tempura is ice-cold water and brief stirring: that way little gluten develops and the batter stays airy.

Breaded chicken pieces

Cut chicken fillet into pieces and season with salt, pepper and paprika.
Set out three plates: flour, beaten egg and breadcrumbs.
Dip each piece through the flour, then through the egg and finally through the breadcrumbs.
Let the coating rest for 10 minutes.
Fry at 175 °C for 4 to 5 minutes until golden brown, until the centre is 75 °C.

Cleaning up and maintenance

Let the oil cool after frying before you strain it. Wipe the pan clean with kitchen paper and then wash it with warm water and washing-up liquid. With a deep fryer with a removable element read the manual for cleaning. Keep the oil in a closed jar, and note what you fried in it: fish gives off a smell to the oil that you don’t want in the next batch of chips.

A lighter alternative

Do you want less fat? An air fryer or the oven gives a crisp result with much less oil. The crust differs from real deep-frying, but for chips, chicken and vegetables it works well. Toss the pieces with a spoonful of oil before they go in the oven or air fryer.

Frequently asked questions about deep-frying

How do I know the temperature without a thermometer?

Drop a piece of bread or a chip into the oil. If the bread turns golden brown in about 30 seconds, you are around 180 °C. A thermometer is still the safest choice.

How often can I reuse the oil?

On average a few times, as long as it is clear and doesn’t foam or smoke. Strain it after each use.

Why do my chips turn soft?

The oil was too cold, you had too much at once, or the chips were still wet. Fry twice and pat well dry.

Can I deep-fry frozen food?

That can be done, for example with pre-fried chips or croquettes, but shake off the ice and fry in small batches. Frozen food makes the oil spatter a lot.

What do I do in case of fire?

Never extinguish with water. Put a lid or fire blanket on the pan, turn off the heat and let it cool.

Deep-frying at a glance

Deep-frying is submerging in oil of 170 to 180 °C.
Use a neutral oil with a high smoke point.
Fill the pan no more than half.
Pat the food dry and fry in batches.
For chips: fry twice.
Drain and salt straight away.
Work safely: never water on burning oil.

Remember this

Deep-frying isn’t about lots of oil. It is about temperature and dry food: hot enough for a crisp crust, dry enough to stay safe, and in batches so the oil stays hot.