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.

One dish makes that feeble steam the objective. Carnitas submerges pork in lard at about 90°C for hours — a temperature at which the mechanism above deliberately does not happen. Oil does get in, but this is confit rather than frying, and the aim is not crispness but cooking in a medium that is not water. Then the heat comes up at the end and every rule in this guide takes over. One pot, two things, in order.

And in one dish the instant surface set is the obstacle. Youtiao has to puff, and once every face has set against the oil there is nowhere left to expand. So two strips of dough are pressed together to manufacture two faces that never meet the oil, and the steam collects between them and forces the whole thing open. Fry a single strip alongside and it barely puffs, which is the proof.

And in another it is the design. Churros are piped from the same paste as an Éclair — flour cooked in boiling liquid, then eggs — and the éclair's page sets the two side by side: baked, the steam pushes the inside out and leaves a hollow shell; fried, the same paste is a solid crisp stick. Nothing about the paste changed, the medium did. An oven delivers its heat from one side and slowly, so the shell is still soft when the steam arrives and can be blown out into a cavity; in 180°C oil every face sets on contact and there is no soft moment to spend. Youtiao's answer to that is to manufacture two faces the oil never touches. The churro's answer is to stop trying: a stick that cannot inflate has to buy its crust from surface area instead, which is what the star nozzle is for. It is a structural part, not decoration.

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 coatings that go into the oil wet

• 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.

All three go into the oil wet. Some coatings do not.

• A starch film cooked and then dried. Bugak paints vegetables with glutinous rice paste and dries them until they snap. There is no water on the surface to defend it and it still comes out ungreasy — because the water that flashes is not on the outside but trapped inside a gelatinised starch film, and it expands all at once and blows that film into a foam. Which is why the fry is three to five seconds.
• A foam itself. The capeado on a Chile Relleno is whipped whites with the yolk folded back in, and it puffs not because water becomes steam but because the air already in it expands. With no steam to defend itself it depends entirely on 180°C setting the egg on contact, and since a foam holding a yolk drains within minutes it has to be used at once.

And all three assume wheat. One common batter is not made of it.

• A flour with no gluten, where the mixing rule inverts. The instruction above to under-mix exists only because wheat develops gluten. Batata vada is dipped in besan — chickpea flour — and its batter is beaten hard for two minutes instead. As farinata puts it about the same flour, besan has more protein than wheat and forms no gluten whatever, because pulse proteins are storage proteins that cannot link up. With nothing to toughen there is nothing for "mix less" to act on, and what lightens the shell is the air beaten in. Ice-cold liquid still applies; the under-mixing does not.

A fourth coating, and a dial the other three do not have

Flour, flour-and-starch and a wet batter all arrive wet — bugak and the capeado above are the exceptions — and each is judged by what it does to steam and oil. A three-stage flour, egg and breadcrumb coating is a different object. It arrives dry, and it is the only one where you also choose whether it is attached to the food or not.

The corpus sets that dial in both directions and says so.

• Pressed on. Tonkatsu presses its panko on firmly for a thick, crunchy shell, and Milanesa presses "so the coating doesn't peel while frying." Chicken Kyiv is the far end: its crust has to work as a container for the butter inside, which is what makes the sealing and the double crumb non-negotiable rather than fussy.
• Deliberately loose. Schnitzel says do not press. Water at the meat's surface flashes to steam exactly as the opening of this guide describes — and against a loose crumb layer that steam has somewhere to go, lifting the coating clear of the meat into a blistered dome. Pressed on hard it has nowhere to go and the coating sets flat.

What decides which you want is what is underneath, and Chicken Kyiv says it of the other three: they have "nothing inside — a split coating there just exposes meat." With nothing to hold in, a coating is free to detach. With something to hold in, it is not.

The crumb is a second dial. Gyukatsu specifies fresh panko because dried crumbs are dense, make a harder shell and need longer in the oil to colour; Kushikatsu crushes its panko fine on purpose, and that is what makes the Osaka version what it is; tonkatsu sits at the coarse end and pays for it in time. Coarser means a thicker shell, and a thicker shell means whatever is inside has to be able to wait for it — which is why tonkatsu gives a 1.5-2cm loin about six minutes at 170°C while schnitzel keeps the same temperature, pounds the meat to a quarter of that, and is done in under two minutes a side.

Which is also where "enough oil to float" has an exception

Below, this guide asks for at least 3cm and enough depth for the food to float. Schnitzel uses about 1cm and does not submerge — and that is the method rather than a compromise. The pan is tilted so hot fat washes over the top, which is what puffs the upper face as well as the lower one. Put it in a deep fryer instead and that action disappears, along with any way of working a coating that has lifted. The warning the depth rule exists for still binds; a wide pan and one schnitzel at a time is how this dish answers it.

A pair of fried parcels with opposite conditions

Samosa fries in barely-warm oil for nearly twenty minutes; Brik fries at 180°C for ninety seconds. Both are folded triangles, and their temperature and time are the reverse of each other.

The reason is the filling. Brik's has almost no free water left — the potato is cooled, the onion salted and squeezed, the tuna wrung out — so there is no steam pushing from inside. That exempts it from the rule in Wrapping and sealing that fried parcels take the thickest wrappers, and lets it use an unusually thin one for something fried. A samosa, by contrast, encloses a filling that still has to cook, so a thick wrapper, low oil and a long time all travel together.

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.

When the wet thing is the dish, there is no last second

The bullet above treats the wet thing as something whose timing you get to choose, and the limit of that answer is to take it off the plate altogether: reviving leftovers records that sauced tangsuyuk "cannot be fully recovered — which is exactly why the sauce is served separately." Where the wet thing is the dish, there is no last second to wait for, and the clock stops being a warning and becomes something to design around.

It is a different soggy from the one at the top of this guide. There, oil gets in during the fry, and the fix is temperature. Here, water goes into starch that has already gelatinised, after the frying is over, and nothing fixes it — chipsi mayai states the end of it: "left standing, the chips inside drink up the moisture from the egg and go soggy. Reheating does not bring the texture back." A crust also re-wets from its own steam with nothing on it at all, which is where the clock starts (serving temperature). Everything below is spent slowing it.

• Buy time before the sauce arrives. Pique macho puts fried potato under meat and sauce, and describes its first fry as "what lets them survive the sauce later" — so the second fry is being spent on durability rather than on colour. The pan is then reduced almost dry, because "ladling liquid over the chips ruins them within five minutes."
• Put something between them. Nachos uses melted cheese as a barrier rather than a topping: a chip is crisp because it is dry, everything piled on it is wet, and "melted fat is what a chip's surface can hide behind" — which is where the instruction to layer until every chip has some comes from. Chile relleno does the same job with arrangement, keeping the caldillo underneath so it cannot run down over the coating, and the thin film of frying oil left on the tortillas in enchiladas is a weaker version of it.
• Run the clock on purpose. Chilaquiles takes the barrier away and tips the chips straight into bubbling salsa, so one to two minutes "is not caution, it is the entire method." Its other instructions are the same decision again — thick chips give in more slowly, and generous salsa coats the outside fast enough that you can lift them sooner.
• Give the dial up. Enchiladas are rolled in sauce, covered in more and baked, so the tortilla is wet throughout and the softening is the point rather than the cost. What the recipe protects instead is the fold: a corn tortilla has no gluten, so what holds it together is gelatinised starch, "supple while it is warm and cracks once it is cold" — however wet it is.

Which of these is available is settled before any of it, by whether the two can be kept apart at all — a fact about the dish rather than about the cook. Tangsuyuk can put its sauce in a bowl beside the plate; chilaquiles with the salsa served separately is a bag of crisps.