Mathematical Modelling of the Drying Kinetics and Optimization of Process Conditions for Tilapia zillii Fillets Dried in a Convection Oven

http://www.doi.org/10.26538/tjnpr/v7i6.29

Abstract

This study investigated the thin layer drying behaviour of Tilapia zillii fillets under various drying conditions in a convection oven. The fish fillet samples were dried in a single layer at 60ºC, 70ºC and 80ºC with the drying air speed varied between 1.5 and 3.5 m/s over a drying period of 10 h. The drying data were then fitted to six thin layer drying models. In addition to the experiments on drying kinetics, a Box-Behnken experimental design with three factors (temperature, fillet thickness and drying time) was used to determine the optimum process conditions that will give a final moisture content of ≤10 wt.%. It was observed that the drying occurred mainly in the falling rate period with the drying rate increasing with increasing temperature and decreasing fillet thickness. The Two-term exponential model gave the best fit to the experimental drying data, with corresponding R2, RMSE and χ2 varying from 0.9988 to 0.9995, 0.00115 to 0.0106, and 3.41 ×10- 5 to 1.39 ×10-4, respectively. Although effective moisture diffusivity follows an Arrhenius-type relation, it is a non-linear function of temperature, fillet thickness and air speed, with a drying activation energy of 13.44 kJ/mol for 5mm fillets dried at air speed of 2.5 m/s. From the response surface optimization studies, it is possible to dry the fillets to a moisture content of ≤ 10wt.% at 65oC and drying time of 6.25 h, provided the thickness of the fillets are within 3.5 mm.