Modelling the influence of hot air on the drying kinetics of turmeric slices

The influence of different drying temperatures and slice thicknesses on the drying kinetics of turmeric slices was studied to show how moisture is removed. The best model for predicting the drying kinetics was also determined. Turmeric slices (3 mm, 5 mm, and 7 mm) were dried at 40, 50, and 60 °C in a laboratory oven dryer. Four thin layer drying models (Newton, Henderson and Pabis, Logarithmic, and Page) were fitted to the experimental data and the selection was done based on the model with the highest correlation coefficient (R2), and lowest reduced chi-square (χ2), the sum of square error (SSE), and root mean square error (RMSE). Drying time varied between 420 min and 1140 min as the air temperature increased from 40 °C to 60 °C. The effective moisture diffusivity coefficient increased with increasing drying temperature and was found to be between 1.35×10-10 m2/s, and 5.00×10-10 m2/s, 3.00×10-10 m2/s and 10.91×10-10 m2/s, and 4.56×10-10 m2/s and 13.00×10-10 m2/s at 40 °C, 50 °C, and 60 °C, respectively. The values obtained for the activation energy for moisture diffusion were found to be 56.809, 56.060, and 45.561 kJ/mol for 3, 5, and 7 mm, respectively. The page model was found to best describe the oven drying of turmeric slices.