THE IMPORTANCE OF PHYSICAL STRUCTURE on the transport of water during hydration kinetics has been demonstrated in sponge cake as model porous system. Deff within sponge cake varied with moisture content and temperature and could be predicted with fair accuracy by simple equations as a function of moisture content. These equations could be easily used in further simulations of moisture transfer in such a material. According to microscopic observations using ESEM, the modifications of apparent degree of porosity of the sponge cake was revealed and confirmed our hypothesis that the level of porosity of the sponge cake could play a dominant role in determining the effective diffusivity.