Sucrose thermal degradation is an important reaction in the food industry. When in concentrated and neutral solutions, pure sucrose presents a lag phase in the reaction. This work aimed at: (i) modelling sucrose thermal degradation autocatalytic behaviour and (ii) studying the concentration and temperature effects on kinetic parameters. Isothermal experiments were conducted at temperatures ranging from 100 to 180 degrees C, using solutions with varying water content (3.58-30.03 (% w/w)). The logistic and Gompertz sigmoidal equations were modified and reparameterised, in order to describe degradation behaviour with kinetic parameters with physical meaning (maximum reaction rate, k(max) and lag time, lambda). In both models these parameters presented an Arrhenius type dependence on temperature. Following a mixed model effect methodology, the concentration dependence was observed on the Arrhenius parameters. This concentration effect was included in the proposed kinetic models, which were able to successfully describe experimental data. (c) 2005 Elsevier Ltd. All rights reserved.