Kinetic aspects of the Maillard reaction: a critical review.

The literature concerning the kinetics of the Maillard reaction was critically discussed according to the initial, intermediate and advanced stages, as this is the way the Maillard reaction is traditionally analysed. For each stage, a division is made between simple kinetics and complex kinetics. Simple kinetics means that the general rate law is used and results are reported as zero-, first- or second-order reactions (sometimes a fractional order). It is emphasized that this approach for a complex reaction as the Maillard reaction only results in a mathematical fit procedure, not in mechanistic insight. The rate constants and activation energies derived are in fact composed of several elementary rate constants. With complex kinetics, i.e. trying to establish the kinetics for individual reaction steps, more mechanistic information can be extracted. However, there are conflicting results in literature and the interpretation is not always correct, as is shown in several examples. A summary of activation energies reported for the various stages in the Maillard reaction reveals large discrepancies, probably reflecting strong effects of experimental conditions on results that are obtained. Careful control of experimental conditions and proper kinetic analysis of the various stages in the Maillard reaction should lead to more consistent results in the future.