Modeling of bread baking with a new, multi-scale formulation of evaporation-condensation-diffusion and evidence of compression in the outskirts of the crumb
Résumé
Porous media approaches to bread baking involving energy, mass transport and continuous mechanics have now been widely explored and can be implemented with commercial software. The challenges now are thorough experimental verification, and understanding of the physicochemical phenomena both on the small scale and the way they are taken into account in continuous macroscopic models. A new evaporation condensation diffusion formulation that idealizes the distribution of bubbles in dough as periodic cubes is presented here. The effects it elicited on water flux, total water loss and variations in local water content were investigated. Additionally, a continuous approach involving four components (dough, CO2, air and water), mass, energy transport and dough deformation was developed. Experimental validation was performed both on usual variables such as temperature, total height and water loss, and on CO2 release, and profiles of local gas fraction and water content The mechanisms of expansion and compression in the expanding dough during baking are discussed for the first time, with the help of both a non-invasive technique (MRI) and numerical simulations. Only two parameters related to the mechanical properties of dough (viscosity and rupture leading to the opening of pores) were tuned; both CO2 release (onset), and local gas fractions (position of the squeezed region) were revealed to be highly sensitive to these parameters. A single set of physically-consistent values was found to reproduce satisfactorily the experimental findings related to the transport and expansion of the gaseous phase.