Maillard reaction kinetics in model preservation systems in the vicinity of the glass transition: experiment and theory.

Rates of reactant consumption for the Maillard reaction between lysine and glucose were measured for a noncrystallizing trehalose-sucrose-water matrix in the glass transition region. At temperatures above the glass transition temperature (T(g)), the consumption rates showed Arrhenius temperature dependence with activation energies of 135 and 140 kJ mol(-1) for lysine and glucose, respectively. Finite reaction rates were observed for glassy samples that were faster than that of one of the nonglassy samples. A comparison of experimental results with predicted diffusion-controlled reaction rate constants indicated that the reaction was reaction-controlled at temperatures above T(g) and approached the diffusion-influenced regime in the glassy state. The needs for further research on reactant diffusivity, the theory of the orientation dependence of reactivity, and a detailed understanding of the reaction mechanism and kinetics were identified.