Water diffusivity within sponge cake was determined at 5, 20, and 25 °C by identification from a
water sorption kinetic and using a mathematical model based on Fick’s 2nd law. Water diffusivity at 20 °C within
sponge cake varied from 0.5 × 10–10 m²/s to 7.5 × 10–10 m²/s as a function of sponge cake moisture content.
Influence of temperature on the concentration-dependent diffusivity was investigated. The activation energy
was found to vary with sponge cake moisture content from 84 to 128 kj/mole. Effective diffusivity variations were
correlated with the changes in microstructure of the material that was observed by using environmental scanning
electron microscopy. The level of porosity in the material played a dominant role in determining the effective
diffusivity.