What Is Searing? Browning a Surface, and Not Sealing Anything

The claim originates with the nineteenth-century chemist Justus von Liebig, who proposed that searing forms an impermeable crust trapping juices inside, and it was repeated by cookery writers for a century. It is straightforwardly false and easy to test. Seared meat continues to release liquid visibly, a seared steak weighed before and after cooking loses a similar or greater proportion of its mass compared with an unseared one, and a crust of browned protein is not waterproof. Harold McGee's work in the 1980s brought the disproof to a general audience and side-by-side experiments have been repeated many times since with consistent results. Searing can slightly increase moisture loss, because the high surface temperature drives off water. The reason the myth persists is that searing does improve the result substantially, so the practice is correct and only the explanation is wrong, which is a combination that makes a false belief unusually durable since following it produces good outcomes.

The benefits are real and concern flavour and texture rather than moisture:

• •The Maillard reaction between amino acids and sugars above about one hundred and forty degrees, which generates hundreds of aroma compounds responsible for the taste of roasted and grilled food
• •Caramelisation of any sugars present, which contributes further flavour and colour
• •Textural contrast between a crisp browned exterior and a soft interior, which is a substantial part of why seared food is satisfying
• •Visual appeal, since brown food looks cooked and pale meat does not, and appearance measurably affects perceived taste
• •Residue in the pan that becomes a sauce when deglazed, which is flavour created by the searing and captured afterwards
• •Rendering of surface fat, which improves both texture and flavour on fatty cuts

The requirements follow from the chemistry and the commonest failures are predictable. The surface must be dry, because water must evaporate before the temperature can exceed one hundred degrees, and any moisture present means the meat steams rather than browns until it has boiled off, which wastes time and overcooks the interior. Patting dry with paper and, for larger cuts, leaving uncovered in a refrigerator for hours works well. The pan must be hot and must stay hot, which is why heavy pans are used and why adding too much cold meat at once drops the temperature and produces grey meat in a puddle. The meat must not be crowded, for the same reason. It should not be moved for the first minute or two, since browning requires sustained contact. And oil should have a smoke point above the working temperature, which rules out unrefined oils and butter alone, though butter added at the end brings flavour without burning.

Two distinct chemical processes produce brown food and confusing them leads to wrong conclusions about temperature and ingredients. The Maillard reaction requires amino acids and reducing sugars together and produces the savoury complexity of roasted meat, bread crust, coffee and chocolate, and it accelerates sharply above about one hundred and forty degrees and in drier and slightly alkaline conditions, which is why a pinch of bicarbonate speeds up browning onions dramatically. Caramelisation involves sugars alone breaking down under heat and requires higher temperatures for most sugars, producing sweeter and simpler flavours. Both are distinct from burning, which is pyrolysis producing carbon and bitterness with no useful flavour. Enzymatic browning, which turns a cut apple brown, is a fourth process entirely, driven by enzymes rather than heat and prevented by acid, heat or exclusion of air. Knowing which process is wanted determines the temperature, the moisture and sometimes the additives, and it explains why the same ingredient browns readily in one preparation and refuses in another.

The order of operations is a genuine choice and the reverse sear has become popular for good reasons. The traditional sequence sears first and finishes in an oven, which is fast and produces a wider band of overcooked meat beneath the surface because the hot exterior conducts heat inward while the centre catches up. The reverse sequence cooks the meat slowly at low temperature until the interior is just below the target, then sears briefly at very high heat, which produces a more evenly cooked interior, a drier surface that browns faster and therefore a shorter exposure to searing heat, and better control since the interior temperature is monitored throughout. Its disadvantages are that it takes longer and suits thicker cuts. Sous vide followed by searing is the same principle taken further. Browning before braising serves a different purpose again, since the liquid will prevent any browning once added, so the flavour must be created first and the crust will soften completely.

Browning creates flavour through the Maillard reaction and does not seal anything, as weighing before and after cooking demonstrates, and the sealing claim traces to a nineteenth-century chemist and survives because the practice itself is worth doing. The surface must be dry, since water must boil off before the temperature can rise enough to brown. Cooking gently first and searing last gives a more evenly cooked interior.