Modelling of Thin Layer Drying Kinetics of Tomato (Lycopersicon esculentum Mill) Slices under Direct Sun and Air Assisted Solar Dryer

Oyerinde. A.S.

Drying experiments were conducted using direct sun drying and indirect passive solar dryer to simulate the drying processes of tomato slices, Tomato slices of 3mm thickness were placed on perforated stainless steel trays in a thin layer and dried to equilibrium moisture content. All samples were dried from an initial moisture content of 95.4 %wb to 10.2 %wb for sun dried samples and 8.5 %wb for solar dried samples. The drying data were fitted with ten published thin layer drying models. Selection of the best model was achieved by comparing the coefficient of determination (R²), reduced chi-square (χ²) and root mean square error (RMSE) between the experimental and predicted values. The diffusion coefficient and activation energy were determined using the Arrhenius equation. The results showed that the Page model was found to best describe both the sun and solar drying kinetics of tomato slices under the conditions tested. Effective moisture diffusivity was 5.07×10^-7m²/s for sun dried and 2.32×10^-7m²/s for solar dried tomato samples, while activation energy ranged from 32.38 to 33.53 kJ/mol for sun dried and 39.14 to 42.12kJ/mol for solar dried samples, respectively. It was concluded that the Page model is applicable to predict moisture content of tomato slices during direct sun and solar drying of tomato slices.