Temperature variation with time within a food item during freezing/thawing can be determined experimentally. However, experimental procedures are often too expensive and time consuming. In order to accurately predict the temperature variation from the numerical solutions of mathematical models, the physical changes that a food item undergoes during phase change have to be well understood. Since freezing or thawing is a heat transfer process with phase change, the Fourier equation for heat conduction (Eq. (1)) can be used to predict temperature distribution in a solid material.