Modelling of thermal pressure forming of starch-based materials Original Research Article

Models describing the pressure baking of starch-based biologically degradable products are reported to explain the surprising temperature and pressure variations observed experimentally. Baking of potato starch suspension in the confined space of a mould is characterised by an initial increase followed by a decrease in temperature of the processed material even if the temperature of the heating walls is constant. The suggested integral model describes processes, which take place inside the liquid core, porous crumb and gradually formed solid crust at the surface. It is assumed, that the temperature of the sample is controlled by steam pressure during the phase of free water evaporation and thus the pressure drop corresponding to the flow of steam through the crumb, crust and along the wall of the heater is analyzed in more details. Volumetric expansion of processed material is attributed to the expansion of the liquid core filled by bubbles of steam.