alpha-Dicarbonyl compounds--key intermediates for the formation of carbohydrate-based melanoidins.

The Maillard reaction of carbohydrates and amino acids is the chemical basis for flavor and color formation in many processed foods. Dicarbonyl compounds, such as 1-, 3-deoxyosones and 1,4-dideoxyosones, as well as short-chain dicarbonyls, such as methylgyoxal or glyoxal, are key compounds of the Maillard browning reaction. The alpha-dicarbonyls are also starting materials for polymerization reactions which lead to formation of carbohydrate-based melanoidins. With regard to the dicarbonyl compound, different possible chemical structures of melanoidins will be discussed. The analysis by size-exclusion chromatography revealed that those colored compounds differ in their molecular size and are directly associated with reactions having specific alpha-dicarbonyl compounds.