Mathematical Modeling on Hot Air Drying of Thin Layer Fresh Tilapia Fillets

The hot convective drying of fresh tilapia fillets was evaluated in a heat pump dryer. The influence of the drying temperature (35,45 and 55 degrees C), hot air velocity (1.50, 2.50 and 3.50 m/s) and thickness (3, 5 and 7 mm) of the tilapia fillets on the moisture ratio and drying rate has been studied. It shows that drying process took place in falling rate periods. The experimental drying data of fresh tilapia fillets under different conditions was fitted to nine different commonly used thin-layer drying models by nonlinear fitting methods and all the models were compared according to three statistical parameters, i.e. coefficient of determination, the reduced chi-square and the root mean square error. It was found that the coefficient of determination values of Page were higher than 0.99254, and the corresponding reduced chi-square and the root mean square error values were lower than 0.000632219 and 0.023854, respectively, indicating that the Page model is the best to describe drying curves of fresh tilapia fillets among them. Effective moisture diffusivity ranged from 6.55 x 10(-10) to 1.23 x 10(-9) m(2)/s calculated using the Fick's second law. With the increase of the drying temperature and the hot air velocity, the effective moisture diffusivities D-eff increased. The value of drying activation energy of tilapia fillets with thickness of 3 mm at hot air velocity 2.50 m/s was 17.66 kJ/mol, as determined from the slope of the Arrhenius plot, ln(D-eff) versus 1/T-a.