The interaction of metal ions with Maillard reaction products in a lactose–glycine model system

The influence of Cu2+, Fe2+ and Zn2+-ions on Maillard model reactions was studied by heat treatment of lactose/glycine model solutions. The presence of metals affected the intensity of browning. Fe2+-ions stimulated the accumulation of colored compounds at all concentrations (20–100 mg/L) tested, Cu2+ and Zn2+ only at the lowest concentrations applied (1 and 5 mg/L, respectively) but to a higher extent. Cu2+ and Zn2+-ions at the highest concentrations applied (5 and 25 mg/L, respectively) suppressed browning of the model mixtures. The relative amounts of metal ions incorporated into the high molecular weight melanoidin fraction increased initially with the reaction time, but near the end of the reaction time studied (5 h, reflux conditions) Cu2+ and Fe2+-ions were released again from the melanoidins. The amounts of metal ions incorporated into the lactose–glycine melanoidins and their influence on Maillard browning of the different fractions depended on the time of interaction and the nature and concentration of the incorporated metals.