Maillard reaction

Lore & Background

The Maillard reaction is a chemical process between amino acids and reducing sugars that produces melanoidins, the compounds responsible for the browned color and distinctive flavor in a wide range of cooked foods, including seared steaks, bread crusts, toasted marshmallows, and fried dumplings. It is a form of non-enzymatic browning that proceeds rapidly at elevated temperatures, though at higher heats, caramelization and pyrolysis become more pronounced. The reaction involves the carbonyl group of a sugar reacting with a nucleophilic amino group from an amino acid, forming a complex mixture of molecules that generate numerous aromas and flavors.

This process is accelerated in an alkaline environment, such as when lye is applied to pretzels to darken them. Hundreds of different flavor compounds can be produced depending on the food’s chemical makeup, temperature, cooking time, and air exposure. The reaction is also responsible for the browning and umami taste in fried onions, coffee roasting, malted barley, dried and condensed milk, dulce de leche, black garlic, chocolate, and roasted peanuts.

Specific compounds like 6-acetyl-2,3,4,5-tetrahydropyridine contribute a biscuit-like flavor in baked goods, while 2-acetyl-1-pyrroline gives cooked rice and pandan their characteristic smells. At high temperatures, a probable carcinogen called acrylamide can form, which can be discouraged by lower heat, adding asparaginase, or injecting carbon dioxide. The Maillard reaction also occurs in dried fruit, aging champagne, and in archaeological contexts, such as preserving bog bodies through slow browning in acidic peat.

Reader's Guide

The Maillard reaction is significant because it is responsible for the browning and flavor development in a vast array of foods, including seared steaks, fried dumplings, cookies, breads, toasted marshmallows, and falafel. It produces hundreds of different flavor compounds depending on the food's chemical constituents, temperature, cooking time, and presence of air.

The reaction is accelerated in an alkaline environment, such as when lye is applied to darken pretzels. At high temperatures, a probable carcinogen called acrylamide can form, which can be discouraged by heating at a lower temperature, adding asparaginase, or injecting carbon dioxide. According to chemistry Nobel Prize winner Jean-Marie Lehn, 'The Maillard is, by far, the most widely practiced chemical reaction in the world.' The reaction also occurs in non-food contexts, such as in archaeology when bodies are preserved in peat bogs, and contributes to the preservation of paleofeces.