Investigation of the contribution of radicals to the mechanism of the early stage of the Maillard reaction

Involvement of radical reactions in the mechanism of the Maillard reaction is demonstrated. Intermediate Maillard reaction product interactions with the stable 2,2-diphenyl-1-picryl-hydrazinyl radical, and also electron transfer, followed spectrophotometrically with phenanthrolin, allowed the contribution of these reactions in the Maillard system to be explored. It was, thus, possible to estimate which reaction mechanism (ionic or radical) dominates the early stage of the Maillard reaction, depending on the milieu and the reactants in a model system.The pH value has a significant influence on the participation of radical reactions. Whereas at pH 5 an ionic mechanism seems to be predominant, at increasing pH values reactions proceed with an increasing amount of radical participation. The influence of the amino acids used is marginal, especially at high pH values. In the glycine model, the amount of ionic reactions rises on changing the pH value from 8 to 7.The sugar influence on the reaction mechanism depends particularly on the ability to form sugar fragments and on the molar ratio of sugar to amino acid.