Diffusional model with and without shrinkage during salted fish muscle drying

The drying process of salted pieces of shark muscle (Carcharhinus limbatus) was accomplished using three air conditions (20 degrees C -40 %RH; 30 degrees C -30 %RH; 40 degrees C -45 %RH) and two air velocities (0.5 m/s; 3.0 m/s). Shrinkage of material during drying was correlated as a linear function between linear dimension and moisture content. The experimental drying data were obtained using both the diffusional model with moisture content parameter (considering no shrinkage) and the diffusional model with moisture concentration parameter (considering shrinkage). The values of effective diffusivity varied between 1.50x10(-10) m(2)/s and 2.85x10(-10) m(2)/s for drying process considering no shrinkage and between 0.87x10(-10) m(2)/s and 1.61x10(-10) m(2)/s for process considering shrinkage. The activation energy was calculated assuming an Arrhenius' type equation. The values were 17.94 kJ/mol with the air velocity of 0.5 m/s and 21.94 kJ/mol with the air velocity of 3.0 m/s for effective diffusivity without shrinkage. The values were 2.04 kJ/mol with the air velocity of 0.5 m/s and 16.12 kJ/mol with the air velocity of 3.0 m/s for effective diffusivity with shrinkage. These low activation energy values, calculated considering the shrinking effect, show that the side effects during drying reduces the effective diffusivity dependence on temperature.