Maillard reaction

The Maillard reaction (/maɪˈjɑːr/ my-YAR; French pronunciation: ​[majaʁ]) is a chemical reaction between amino acids and reducing sugars that gives browned food its desirable flavor. Seared steaks, pan-fried dumplings, biscuits (widely known in North America as cookies), breads, toasted marshmallows, and many other foods undergo this reaction. It is named after French chemist Louis-Camille Maillard, who first described it in 1912 while attempting to reproduce biological protein synthesis.

The reaction is a form of non-enzymatic browning which typically proceeds rapidly from around 140 to 165 °C (284 to 329 °F). At higher temperatures, caramelization and subsequently pyrolysis become more pronounced.

The reactive carbonyl group of the sugar reacts with the nucleophilic amino group of the amino acid, and forms a complex mixture of poorly characterized molecules responsible for a range of odors and flavors. This process is accelerated in an alkaline environment (e.g., lye applied to darken pretzels), as the amino groups (RNH₃⁺) are deprotonated and, hence, have an increased nucleophilicity. The type of the amino acid determines the resulting flavor. This reaction is the basis of the flavoring industry. At high temperatures, a potential carcinogen called acrylamide can be formed.