Heat-induced changes in dairy products containing sucrose

Abstract

The aim of the present work was to analyse the influence of the variables reaction temperature, casein-sucrose ratio and pH, on the kinetic parameters of gelation reactions, the gelation time and the functionality of casein micelles in concentrated milk systems containing sucrose. Global constant rate reaction order of gelation and were calculated, the first varying between four different orders of magnitude and the second between 1 and 7. Mathematical models allowing the prediction of gelation time with a good fit (r2 > 0.94) were obtained. Activation energy (Ea) for gelation decreased as pH decreased. In presence of sucrose, Ea values showed a higher temperature dependence. Gel functionality showed to be pH independent. Although the kinetic aspects of the reactions were affected by pH, the thermodynamic ones remained almost unchanged. Aggregation and gelation were very fast at pH 6. When comparing gelation kinetics with those corresponding to fluorescence and colour development, gelation showed to be produced much earlier than the latter two phenomena.