3.4 Effective diffusion coefficient
Figure 4 shows different drying curves of coffee extract from 65 % dry matter content to the
concentration corresponding to the humidity of the surrounding air, maintained by a super-saturated salt
solution. The final equilibrium value leads to the desorption isotherm represented in figure 6 (right). The
drying curves were analyzed using the analytical solution according to Crank [3] as represented in
equation 1.