Mathematical modeling of the drying curves
Fig. 1 shows the exponential tendency of experimental drying curves for all working temperatures where it is observed that drying time decreases as temperature is increased to reach similar final moisture content. Overlapping of the drying curves at 60, 70 and 80 °C could be explained due to formation of a hardening of the surface area of the squid sample related to the osmotic pre-treatment. This crust presents significant resistance to water migration from within the cell reducing the drying rate (Bellagha et al., 2002 and Mujaffar and Sankat, 2005). This effect is overcome at high air-drying temperature (e.g. 90 °C) where heat transfer promotes faster evaporation and thus enhances the exits of water vapor by diffusion. When analyzing the effective moisture diffusivity at each temperature, four homogenous groups were found (50 °C, 60–70 °C, 80 °C and 90 °C).