The Maillard reaction is a chemical reaction between an amino acid and a reducing sugar, usually requiring the addition of heat. Like caramelization, it is a form of non-enzymatic browning. The reactive carbonyl group of the sugar interacts with the nucleophilic amino group of the amino acid, and interesting but poorly characterized odor and flavor molecules result. This reaction is the basis of the flavoring industry, since the type of amino acid determines the resulting flavor.

In the process, hundreds of different flavor compounds are created. These compounds in turn break down to form yet more new flavor compounds, and so on. Each type of food has a very distinctive set of flavor compounds that are formed during the Maillard reaction. It is these same compounds that flavor scientists have used over the years to create artificial flavors.

Although used since ancient times, the reaction is named after the chemist Louis-Camille Maillard who investigated it in the 20th century.

Foods with Maillard reactions

• 'caramel' made from milk and sugar
• the browning of bread and toast
• the colour of beer, chocolate, coffee, and maple syrup
• self-tanning products
• the flavour of roast meat
• the color of dried or condensed milk

The process

1. The carbonyl group of the sugar reacts with the amino group of the amino acid, producing N-substituted glycosylamine and water
2. The unstable glycosylamine undergoes Amadori rearrangement , forming ketosamines
3. There are several ways for the ketosamines to react further:
   • Produce 2 water and reductones
   • Diacetyl, acetol , pyruvaldehyde and other short-chain hydrolytic fission products can be formed
   • Produce brown nitrogenous polymers and melanoidins

Factors

Pentose sugars react more than hexoses, which react more than disaccharides. Different amino acids produce different amounts of browning.

Since the Maillard reaction produces water, having a high water activity environment inhibits the reaction.

See also

• Baking
• Advanced glycosylation end products

External links

• Course website on Maillard reaction