A numerical model of the coffee roasting process under operating conditions is proposed. This numerical tool is able to simulate the behaviour of all the components of a batch roaster as well as the roasting process of the coffee beans within the drum. The model evaluates the heat and mass transfer between a hot air flow and the coffee beans during the roasting process on the basis of the physical properties of the coffee and the operation of the roasting machine. Different submodels are included in the modelling in order to address particular thermo-physical processes, such as the evaporation of coffee moisture and the heat released or absorbed by the beans due to the roasting reactions. The proposed numerical model is thus able to predict the performance of the coffee roaster in terms of pressure, temperature and mass flow rate in the main sections of the system, as well as fuel consumption. In addition, the temperature profile of the coffee beans within the roasting drum is evaluated as a function of the system's working conditions. Different roasting machine control strategies can therefore be compared and the effects on the coffee roasting profile can be analyzed. Experimental data in the literature on a laboratory roaster are used as a reference to validate the results provided by the numerical model. Finally, the tool's predictive capabilities are addressed by simulating an industrial coffee roasting machine. (C) 2012 Elsevier Ltd. All rights reserved.