Modeling the mechanisms of dough puffing during vacuum microwave drying using the finite element method

A two-dimensional finite element (2-D FE) model was developed in order to simulate the puffing of a dough ball being dehydrated under vacuum with microwave energy. The model enabled the coupling of thermal and solid mechanics effects providing an insight into the mechanisms of puffing of food stuffs during vacuum microwave dehydration. The model predicted the rise in temperature reasonably well for low salt contents. The model suggests puffing is due to two mechanisms: first, the difference in pressure between air trapped in the dough and the chamber pressure of the vacuum microwave dehydrator; second, the generation of vapour due to the temperature rise in the dough. The temperature distribution is primarily determined by the penetration depth of the microwaves into the material. It was further shown that the partial collapse of dough balls in the later stages of the drying process can be attributed to the softening of dough at higher temperatures and air loss throughout the drying process.