A mechanistic model for baking of leavened aerated food

• Viscoelasticity is described by Oldroyd B constitutive equation.
• Bubble expansion due to heating, moisture evaporation and CO2 diffusion accounted for.
• Model predicted the evolution of moisture and density profiles during baking.
• An expanded uniform inner region and an increasing denser surface crust predicted.
• Predicted dough rise and force exerted by rising dough compared with experiments.

A mechanistic model for baking of leavened aerated food is proposed. The model accounts for heat conduction, moisture diffusion, diffusion of CO2 that is produced by fermentation, and the resistance to bubble expansion by the viscoelasticity of the dough which is described by Oldroyd B constitutive equation. Unsteady state heat conduction and moisture diffusion equations are solved accounting for bubble expansion due to heating, evaporation of moisture as well as diffusion of CO2 that is produced by fermentation to obtain the evolution of temperature, moisture and air volume fraction profiles as well as dough rise. The bubble expansion due to CO2 diffusion is coupled to temperature and moisture profiles. The model predicts that the growth of bubble exhibits a lag time followed by an exponential growth phase consistent with experimental observations. Eventhough the surface region is more expanded initially, at longer times, it is found to be more dense. The calculated air volume fraction profiles at longer times indicated an expanded inner region of more or less uniform density and a denser surface crust region of decreasing air volume fraction (or increasing density). The thickness of the crust region is found to increase with baking time. The average air volume fraction is found to increase with time because of the combined effects of air expansion as well as CO2 diffusion. The model predictions of dough rise as well as force exerted by the rising dough compare well with the experimental data (Singh and Bhattacharya, 2005; Romano et al., 2007).