Nonenzymatic Browning in Liquid Model Systems of High Water Activity: Kinetics of Color Changes due to Caramelization of Various Single Sugars

The kinetics of color changes due to caramelization of various single sugar solutions (fructose, xylose, glucose, maltose, lactose, and sucrose) of water activity adjusted to 0.90 (by adding NaCl) and heated at various temperatures (45–65°C) was studied. A zero‐order and a “mixed”‐order kinetic model were satisfactorily used to describe the rate of color formation. Fructose and xylose solutions browned much more rapidly than those of maltose, glucose, lactose or sucrose. Activation energies for color development of fructose and xylose were in the range 25–30 kcal/mole, while for lactose and maltose they were 35–48 kcal/mole. Lowering of pH inhibited caramelization browning of sugar solutions. The role of hydrolysis in the browning of heated sucrose solutions was studied.