Kinetic modelling of reactions in heated disaccharide–casein systems

The reactions occurring in disaccharide–casein reaction mixtures during heating at 120 °C and pH 6.8 were studied. The existence of two main degradation routes were established: (1) Isomerisation of the aldose sugars lactose and maltose in their ketose isomers lactulose and maltulose, respectively, and subsequent degradation. Lactulose was degraded into galactose and formic acid, whereas maltulose was degraded into glucose and formic acid among other unidentified reaction compounds. (2) The Maillard reaction, in which the aldose sugars and sugar degradation products react with the protein, eventually leading to the formation of brown compounds. Based on these reactions a kinetic model was built and extensively tested using multiresponse modelling. The iterative process of kinetic modelling—proposing a model, confronting it with experiments and criticising the model—was passed through several times. The final kinetic model was able to describe the observed changes in reactants and products and allowed a quantitative prediction of reactions in heated disaccharide–casein systems.