Effect of hexanal and iron on color development in a glucose/phenylalanine model system

Aqueous glucose/phenylalanine (0.1 M with respect to each reactant) systems were heated in an autoclave for 30 min at 140 degrees C, in the presence of hexanal (0.04, 0.1, and 0.2 M) or FeCl(2) (0.01 M). Results show that hexanal significantly inhibited color development at pH 5 and 6 and led to an increase of 5-(hydroxymethyl)furfural. Iron addition had similar effects at pH 5, but only small effects at pH 6. The reaction routes proposed give key roles to the alpha-dicarbonyl compounds, to the Strecker aldehyde, and to the Schiff base formed by the reaction between hexanal and phenylalanine.