Maillard reaction
The chemical reaction between amino acids and sugars that browns food and creates roasted, savoury flavours.
Also: browning reaction
The Maillard reaction is named after the French chemist Louis Camille Maillard, who described it in 1912. When food is heated, amino acids and certain sugars react and form hundreds of new flavour and colour compounds. It becomes rapid above about 140 degrees Celsius, which is why food browns when fried, roasted or grilled but not when boiled. A dry surface helps. The crust of bread, seared meat, roasted coffee and toasted nuts owe their taste to it.