Deep Frying: Temperature, Batter, and the Second Fry

Frying trades water for oil

Put food in hot oil and the water at its surface flashes to steam. That violent outward bubbling is what keeps the oil from getting in. Which is why properly fried food is not greasy.

Run the oil too cool and the steam is feeble, so oil seeps into its place. Soggy fried food is food that absorbed too much oil, and the cause is almost always temperature.

There are two temperatures

• First fry, below 170°C: cooks the interior. Almost no colour.
• Second fry, around 190°C: drives off the last surface moisture and browns it.

Fry once and you have to do both jobs at the same time, so either the outside burns before the inside is done, or you pull it out barely coloured. It is why Tangsuyuk, Karaage and the chips in Pique Macho are all fried twice. The chemistry of the colour is in Browning and the Maillard reaction.

Judging the temperature

A thermometer is best, but a drop of batter tells you a lot:

• Sinks to the bottom and rises slowly → below 150°C, too cool.
• Sinks partway and comes straight back up → 170–180°C, right.
• Never sinks and spreads on the surface → above 200°C, too hot.

A wooden chopstick dipped in should throw a fine, steady stream of bubbles.

Three kinds of coating

• Flour alone: a thin, hard shell. It does not stay crisp for long.
• Flour plus starch: potato or corn starch makes it much lighter and crisper for longer, because less gluten means less toughness. Karaage, Tangsuyuk.
• A wet batter: ice-cold water and flour, deliberately under-mixed. Mix it well and gluten develops into a thick, chewy jacket. The thin, ragged crust of Tempura is the result of not mixing; Fish and Chips adds carbonation for extra bubbles.

Batter liquid should be as cold as you can get it. A big temperature gap makes the surface puff violently and set open rather than dense.

Do not crowd the oil

A lot of food at once drops the oil temperature hard, the steam weakens, and — per above — oil moves in. Never cover more than two-thirds of the oil's surface. It is exactly the same rule as not crowding a pan.

Looking after the oil

• When it darkens and starts smoking at a lower temperature than it used to, it is finished.
• Scoop out the crumbs. Left in, they burn and pass bitterness to everything.
• Cooled, strained through a fine sieve or paper and sealed, it is good for another two or three uses. Oil used for fish is best not reused.
• Depth: enough for the food to float, at least 3cm. Shallow oil swings wildly in temperature.

What you do after draining matters

• Do not pile it on paper towel. The bottom layer steams itself soggy. One layer on a rack.
• Salt it the moment it comes out, while it is hot. Cold food will not hold salt.
• Sauce it at the last second. Pour the sauce over Tangsuyuk early and the crust collapses within five minutes.
• Coatings like the sugar on Churros also only stick while hot.