A critical appraisal of the kinetic model for the Maillard browning of glucose with glycine

A critical analysis of kinetic data for the loss of sulphite species, S(IV), in the glucose-glycine–S(IV) reaction, and the browning (A470) of glucose–glycine mixtures (pH 5.5, 0.2 mol l−1 acetate buffer, 55°C) confirm the accuracy of the 3-step model (proposed by Davies, C.G.A., Wedzicha, B.L., & Gillard, C. 1997). (Kinetic model of glucose–glycine reaction. Food Chemisty, 60, 323–329). Rate constants k1 and k2 are obtained by regression of [S(IV)]-time data to the integrated rate equation for the glucose–glycine–S(IV) reaction. It is confirmed that neither rate constant depends on [S(IV)]. The integrated rate equation for the overall browning reaction is derived, and the rate constant k3 for melanoidin formation as well as the effective extinction coefficient E are obtained by regression. The value of E is confirmed for high molecular weight (Mr>3500) melanoidins by a radiochemical technique based on 14C-labelled glucose. This paper thus presents a protocol to obtain values of the significant rate constants in the browning of aldoses with amino acids.