EXPERIMENTAL STUDY ON VARIABLE TEMPERATURE DRYING PROCESS OF PADDY BASED ON GLASS TRANSITION

To improve the quality of paddy, reduce post-production losses, and ensure processing efficiency, this paper proposes a variable-temperature drying process based on the glass transition phenomenon, using the relationship between paddy moisture content and glass transition temperature. An optical three-dimensional scanning method was employed to obtain the paddy grain particle model. Subsequently, a heat and mass transfer model for paddy was constructed to analyze the temperature distribution and moisture migration behavior during drying. Experiments were conducted using a constant temperature of 40 ℃ and heating amplitudes of 5 ℃, 10 ℃, and 15 ℃ to investigate the drying characteristics and quality evolution of paddy. The simulation results showed that the average errors for moisture content and temperature were 1.58% and 2.66%, respectively. Compared with constant temperature drying at 40 ℃, the variable-temperature drying with heating amplitudes of 5 ℃, 10℃, and 15℃ reduced the drying time by 19, 58, and 63 minutes, respectively. Among the tested conditions, the 5 °C heating amplitude yielded the best results, with a crack increase rate of only 2.5% and a head rice yield of 68.3%. These findings offer valuable insights for understanding the mechanism of variable-temperature drying and for optimizing the drying process of paddy.