The freezing time of foods can be calculated by any of the following classes of methods: analytical formulas, empirical formulas or numerical methods. Numerical methods such as the finite difference method (FDM) or finite element method (FEM) are rigorous and precise.
However, not all food technologists have the skills to write a numerical program or have access to commercial software.
An even more serious drawback is that to take full advantage of a numerical program, the functions relating food thermal properties such as thermal conductivity, density and enthalpy to temperature must be available, which is rarely the case. Although predictive methods and programs for food properties are available, such as COSTHERM (Miles et al., 1983) or the method used later in this paper, they are still subject to errors due to the assumptions made.