Kinetics of the Early Maillard Reaction During Heating of Milk

Study of the kinetics of the heat-induced Maillard reaction in milk is difficult due to competing reactions of lactose: it is also involved in isomerization and degradation reactions yielding lactulose, galactose and formic acid as the main products. To unravel the reaction network in which lactose is involved in heated milk, the protein-bound Amadori product was isolated and heated: the main reaction products were lactose, galactose and formic acid. A kinetic model was established that takes into account both isomerization/degradation and the Maillard reaction. This model consisted of coupled ordinary differential equations which were solved by numerical integration and fitted to experimental data to obtain reaction rate constants. The model was able to describe the course of the reaction in heated milk for 0-15 min at 110-150 °C, but not at longer heating times, especially not at 150 °C, probably due to interference of advanced Maillard reactions. Overall, the degradation of lactose via isomerization/degradation was quantitatively of more importance than via the Maillard reaction.