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 °C, in the presence of hexanal (0.04, 0.1, and 0.2 M) or FeCl2 (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 α-dicarbonyl compounds, to the Strecker aldehyde, and to the Schiff base formed by the reaction between hexanal and phenylalanine.