Time-temperature dependent modelling of the thin-layer drying kinetics ofglutinous rice

Understanding the grain’s response to temperature during the drying process requires careful observation of the drying kinetics. In this study, freshly harvested glutinous rice was dried in hot air under different temperatures: 50℃, 60℃ and 70℃ and the drying kinetics were monitored throughout the drying process. The experimental data were fitted into five commonly used mathematical models: Newton, Henderson and Pabis, Page, Peleg, and Logarithmic. To further explain the impact of temperature on the drying kinetic model, a secondary model with time-temperature features was developed. The result shows that the initial moisture content of the glutinous rice was 21.5% and it was reduced to 8% in ~5 hrs under 70℃ and the drying time increased progressively with the reduction in the temperature. The effective moisture diffusivity of the grain increased from 1.09×10-8 m 2 /s to 2.52×10-8 m 2 /s as the temperature increased from 50℃ to 70℃ with an activation energy of 41.1 kJ/mol. Compared to other primary models, the Page model had the best performance with 0.999 ≤ R² ≤ 1.00, and 0.0014 ≤ RMSE ≤ 0.036. The secondary model with 99.64% prediction accuracy is suggested for predicting the drying kinetics of glutinous rice as a function of the time and temperature of the drying process.