Recent advances in the chemistry of Strecker degradation and Amadori rearrangement: Implications to aroma and color formation

The importance of Strecker degradation lies in its ability to produce Strecker aldehydes and 2-aminocarbonyl compounds, both are critical intermediates in the generation of aromas during Maillard reaction, however, they can also be formed independently of the pathways established for Strecker degradation. Strecker aldehyde can be formed directly either from free amino acids or from Amadori products. Several pathways have been proposed in the literature for the mechanism of this transformation. On the other hand, Amadori or Heyns rearrangements of ammonia,with reducing sugars can also generate 2-aminocarbonyl compounds without the formation of Strecker aldehyde. In addition, isomerization of the imine bond of the Schiff base formed between a reducing sugar and an amino acid, can initiate a transamination reaction and convert the amino acid into the corresponding alpha-keto acid and the sugar into its alpha-amino, alcohol derivative. The reverse of this reaction, has been documented to produce Amadori products. The alpha-keto acids can either decarboxylate to produce Strecker aldehydes or undergo Strecker degradation (as a alpha-dicarbonyl compound) with amino acids to also produce Strecker aldehydes. This review will examine the role of Strecker degradation and Amadori rearrangement, under the light of recent findings, in controlling the balance among four critically important key intermediates: alpha-dicarbonyl, alpha-hydroxycarbonyl, 2-amino carbonyls and 2-(amino acid)-carbonyl compounds, during the Maillard reaction and hence control relative importance of aromagenic versus chromogenic pathways.