Cooking · Browning above 140 °C

Maillard reaction

The Maillard reaction is the chemical reaction between amino acids and reducing sugars that turns the surface of a steak brown and creates hundreds of aroma compounds: roasted, nutty, meaty. It becomes fast above about 140 °C / 284 °F, which a wet surface cannot reach while its water boils off, and it is the main reason seared meat tastes different from boiled meat.

Also known as: Reacción de Maillard · Phản ứng Maillard · Réaction de MaillardLast reviewed 25 Oct 20265 sources

A network of reactions, not one

The Maillard reaction is not one reaction but a network of them, first described in 1912 by the French chemist Louis-Camille Maillard, who heated amino acids with sugars and watched them brown. The pathway was mapped by the American chemist John E. Hodge in 1953, and it is responsible for the colour and much of the flavour of bread crust, roasted coffee, toasted nuts, fried onions and seared meat.

On a steak it produces the brown crust and its aroma: roasted, savoury, nutty and meaty notes that raw or boiled beef does not have. It is often confused with caramelisation, which is the browning of sugars alone at higher temperatures; meat contains very little free sugar, so the browning of a steak is almost entirely Maillard chemistry, with a contribution from the breakdown of fat.

From sugar and amino acid to crust

The reaction begins when the carbonyl group of a reducing sugar (in beef, mainly glucose and ribose, the latter released from the breakdown of nucleotides after slaughter) combines with the amino group of an amino acid, peptide or protein. The unstable product rearranges, fragments and recombines with other molecules, producing hundreds of compounds: pyrazines (roasted, nutty), thiazoles and thiophenes (meaty, sulphur-containing, from cysteine and methionine), furans (caramel-like), and brown polymers called melanoidins that give the crust its colour.

The reaction occurs at any temperature but is extremely slow at room temperature and in the cooking range of the interior of a steak. It accelerates steeply with heat and becomes fast enough to brown a surface in seconds or minutes above about 140 °C / 284 °F. It is also strongly affected by water: water dilutes the reactants and, as long as a surface is wet, it cannot rise above the boiling point of 100 °C / 212 °F. A slightly alkaline surface browns faster; an acidic one, slower.

Beyond about 180–200 °C / 356–392 °F for extended periods, browning gives way to pyrolysis: the surface chars, bitter and acrid compounds dominate, and potentially harmful substances such as heterocyclic amines and polycyclic aromatic hydrocarbons form in larger amounts. A good crust is deep brown, not black.

Temperatures

Step by step: getting the reaction

1. Dry the surface: pat the steak with paper, or leave it uncovered on a rack in the refrigerator for several hours or overnight, which dries the outer layer further.
2. Salt either at least 40 minutes before cooking, so the drawn-out brine is reabsorbed, or immediately before; see Salting steak.
3. Preheat the pan, plancha or grill well above 200 °C / 392 °F, so that the metal or embers have enough stored heat to evaporate any moisture instantly.
4. Use a thin film of oil with a high smoke point; the oil fills the gaps between meat and metal and transfers heat evenly.
5. Leave the steak in contact until it releases and is brown, turning it often enough that the inside does not overcook; flipping every 30–60 seconds also gives a good crust.

Salt before or after

Salt draws water out of the meat by osmosis within a few minutes, so a steak salted 3–30 minutes before cooking sits in a film of brine that must boil off before browning starts. After about 40 minutes, the dissolved salt and water are reabsorbed into the meat and the surface becomes dry again; after several hours uncovered it is drier than unsalted meat. Salting just before the steak hits the pan also works, because the brine has not had time to form. The practical rule, documented in J. Kenji López-Alt's tests, is: salt at least 40 minutes ahead, or right before; not in between.

Wet, crowded, moved too soon

Putting a cold, wet steak into a pan that is not hot enough, so the surface boils grey instead of browning. Crowding the pan: several steaks release more water and cool the metal more than it can recover. Moving the steak constantly in the first seconds, before a crust forms and releases it. Believing the crust "seals in the juices": it does not; it is there for flavour (see Searing). And confusing black with brown: charred meat is bitter, not more Maillard.

Frequently asked questions

Sources

5

1. McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen, rev. ed. New York: Scribner, 2004.
2. Myhrvold, Nathan; Young, Chris; Bilet, Maxime. Modernist Cuisine: The Art and Science of Cooking. Bellevue: The Cooking Lab, 2011.
3. Toldrá, Fidel (ed.). Lawrie's Meat Science, 8th ed. Duxford: Woodhead, 2017.
4. Hodge, John E. "Chemistry of browning reactions in model systems." Journal of Agricultural and Food Chemistry 1, no. 15 (1953): 928–943.
5. López-Alt, J. Kenji. The Food Lab: Better Home Cooking Through Science. New York: W. W. Norton, 2015.

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