A 3D numerical model for bread dough proofing is presented in this study. It is based on a thermomechanics approach and couples the structural evolution of the dough with chemical kinetics taking place during proofing. The present paper is devoted to the modelling scheme and to a topological analysis of the dough foaming during proofing. The model is governed by a chemical reaction which creates carbon dioxide (CO2), which induces the growth of bubbles embedded in a representative volume of dough (1 mm(3)). The results show how the proofing step confers to the dough a final foam structure, with open or close cells. The trends of the model are in qualitative agreement with experimental data. Finite element simulations show the potentiality of the model to describe these phenomena, including the final cellular structure of the crumb.