The alterations of porosity as a function of boiling period and freeze-drying conditions are visualized with SEM photographs and presented in Fig. 12. Scanning microscope was operated at 500x magnification. As it can be seen, the increase of boiling time leads to noticeable changes of microstructure of cooked rice kernels. At higher boiling periods both porosity and average pore size seemed to increase. Porosity depends on the water uptake and is higher at longer boiling times where water uptake is higher. In addition, as far as freeze-drying pressure is concerned, when the absolute pressure in the freeze-drying chamber is higher, then the porosity is lower compared to the low process pressures.