Vol. XVIII · Meat and Poultry Plate 3 of 11juiciness, juice loss, cooking loss, searing myth, sealing in juices, core temperature, overcooking, resting, moisture, carryoverMH

Juiciness.

Searing to "seal in the juices" is the most repeated myth in cooking. Measure a seared steak and an unseared one to the same doneness: the seared one loses more.

A muscle is a bundle of water-filled fibres in collagen sheaths. As it heats past about 45 °C the fibres' proteins contract (VI.5), and above about 60 °C the collagen sheaths shrink too and wring the fibres like a towel. The juice that comes out — water with dissolved proteins and salts — is lost to the pan or evaporates. Cooking loss therefore rises steadily with temperature: little up to 50 °C, about a fifth by 65 °C, a third by 80 °C. That is the single largest factor in whether meat is juicy.

Searing does many good things — browning and flavour (VIII), a crust, a safe surface — but it does not seal. A browned surface is porous; you can hear it sizzle as juice keeps escaping. In fact a sear adds a band of very hot, overcooked meat under the surface, so for the same centre temperature a seared piece loses a little more. The workshop measures it.

Below: juice lost from a 30 mm beef steak cooked in a 150 °C oven to the pull temperature you choose, with or without a two-minute sear first (thermal bench, juice loss from each layer's highest temperature), against the centre temperature it reaches after an eight-minute rest.

What you will learn
Workshop
Thermal bench: 30 mm beef steak from 5 °C; oven at 150 °C until the centre reaches the pull temperature, optionally after a two-minute sear on a 250 °C pan turned once; then eight minutes resting. Juice loss from each layer's highest temperature (the course loss curve, shaped on published cooking-loss data for beef) plus surface evaporation.

The thermometer keeps the juice in

In this model, a steak pulled at 55 °C and rested to about 57 °C loses about 16 % of its weight if roasted plainly and 20 % if seared first; taken to 72 °C it loses 32 %. So the sear costs a little juice — worth paying for its flavour — and the doneness costs a great deal. Pulling a few degrees earlier saves more juice than any technique.

Resting matters less than legend says. A rested steak loses less on the board when cut, partly because the juice has thickened as it cooled, but the total lost from raw to plate is similar; the larger reason to rest thick roasts is to let carryover finish the cooking evenly (II.9). Other things that help: brining (XVIII.4), which lets the fibres hold more water; fat and gelatin, which make meat taste juicy even when it has lost water (that is why braised shin feels succulent at 90 °C); and slicing across the grain (XVIII.10).

At the stove

Weigh two similar steaks raw. Sear one and not the other, cook both to the same core temperature, rest them, and weigh again. Then cook a third to well done and weigh it.

The sealing idea goes back to the German chemist Justus von Liebig in the 1840s, who argued that searing coagulated the surface and kept juices in. Experiments in the 1930s showed seared roasts lost as much or more; the myth has outlived the experiments by ninety years.

Terms

Cooking loss
The weight a piece loses in cooking, mostly juice and evaporated water.
Sealing myth
The false idea that searing keeps juices in.
Carryover
The rise in core temperature after cooking stops (II.9).
Perceived juiciness
How juicy meat tastes, helped by fat, gelatin and saliva.
Juice loss rises with core temperature, as shrinking collagen wrings the fibres. Searing does not seal. Keep meat juicy by not overcooking it.

Sources

  1. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
  2. Differential scanning calorimetry of muscle: myosin denatures around 54–58 °C, collagen shrinks around 60–67 °C, actin around 70–80 °C (A. Wright, I. B. Leach and P. Wilding, "Differential scanning calorimetric studies of muscle and its constituent proteins", J. Sci. Food Agric. 28, 1977; H. McGee, On Food and Cooking, 2004). The course uses midpoints within these ranges.
  3. H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.