Vol. XV · Dry Heat Plate 8 of 11grilling, broiling, barbecue, radiant heat, two-zone fire, direct heat, indirect heat, flare-ups, charcoal, chicken thighsHS

Grilling and Broiling.

Chicken thighs left over hot coals char black before their centres are safe. Moved to the cool side after colouring, they finish juicy.

A bed of glowing charcoal is at 700–1 000 °C and radiates heat that rises with the fourth power of its temperature (II.4): food a few centimetres above it receives far more heat than from hot air at the same distance. A broiler (an oven's top element, or a salamander) does the same from above. That intensity browns and chars quickly — good for thin pieces, a problem for thick ones, whose surfaces blacken before the inside cooks.

The answer is the two-zone fire: pile the coals on one side, or light only some burners. Food is coloured over the direct heat, then moved to the indirect side, where it cooks through in hot air like an oven with the lid down. The other hazard is flare-ups: fat dripping onto coals vaporises and ignites, licking flames that soot and char; trim excess fat, keep a cool zone to move food to, and do not douse them with water. The workshop grills chicken thighs.

Below: the centre and the face of a 25 mm chicken thigh grilled over direct heat throughout, against 6 minutes direct then indirect at 180 °C (thermal bench), with the 80 °C target for thigh and the minutes to it, and the hottest the face reaches.

What you will learn
Workshop
Thermal bench: chicken thigh, 25 mm, from 5 °C; direct heat modelled as radiation from coals at 700 °C with a view factor of 0.5, turned every 3 minutes; indirect heat as a 180 °C oven. Thigh is preferred at about 80 °C for tenderness (safe from 74 °C).

Colour over the coals, cook beside them

Over 700 °C coals throughout, the thigh reaches 80 °C in about 17 minutes in this model, but its face passes 474 °C — char, not browning. Six minutes over the coals and then the cool side takes 26 minutes, with the face peaking near 125 °C: well browned, not burnt, and the meat juicy. Thin foods — prawns, sliced vegetables, minute steaks, satay — can stay over direct heat; anything thicker than about 2 cm usually wants two zones.

Practical grilling. Let charcoal burn until covered in grey ash before cooking; clean and oil the grate; keep the lid handy (it turns the grill into an oven); move food away from flare-ups rather than spraying water; cook to temperature with a thermometer (XII.6); rest briefly. Marinades with sugar (teriyaki, char siu, 烧烤 glazes) burn fast: brush them on near the end. Charring makes PAHs and heterocyclic amines; trimming fat, avoiding flare-ups and not eating blackened bits keeps them down.

At the stove

Build a two-zone fire, or light one side of a gas grill. Grill chicken thighs over the hot side until marked on both faces, then move them to the cool side with the lid down, checking with a thermometer until 80 °C.

Barbecue traditions span the world — Korean bulgogi, Japanese yakitori over binchōtan charcoal, Xinjiang lamb skewers (羊肉串), Argentine asado — and almost all of them balance direct and indirect heat by raising, lowering or moving the food.

Terms

Radiant heat
Heat carried by infrared radiation from a hot source.
Two-zone fire
A grill with a hot direct side and a cooler indirect side.
Flare-up
A burst of flame from fat dripping onto coals.
Broiler
An overhead radiant element; a grill from above.
Grills cook by intense radiation: thin foods over direct heat, thick ones coloured there and finished on the indirect side. Move away from flare-ups.

Sources

  1. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
  2. H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.