Kinetics and Temperature Dependent Moisture Diffusivities of Pumpkin Seeds During Drying

Abstract

Pumpkin seeds were soaked in 25% w/w NaCl solution for 1 h before hot-air drying with a tray dryer or a fluidized bed dryer (FBD) at drying temperatures of 60, 70 and 80°C. The FBD was operated at an air velocity of 1.8 m/s and a bed depth of 3 cm, whereas the seeds were dried as a single layer in the tray dryer with the air velocity over the sample in the range 0.23–0.28 m/s. The experimental data was fitted into four thin-layer drying models namely the Page, Lewis, Wang and Singh, and two-compartment models. The drying rate constants and coefficients of the models tested were determined by non-linear regression analysis. Among the various models, both the Page model and two-compartment model were
the best-fit models for the three drying conditions. Effective moisture diffusivities of pumpkin seeds determined by applying Fick’s second law of diffusion and the method of slope ranged between 7.69 × 10^-11 and 50.96 × 10^-11 m²/s. The temperature dependence of the effective moisture diffusivity followed an Arrhenius relationship with the activation energies between 15 and 62.12 kJ/mol.