Modeling and Optimization of Infrared-Convection Drying Parameters and Slice Thickness of Onion Slices: Effects on Drying Kinetics and Physicochemical Quality.

The infrared heating process is one potential method for enhancing food quality while speeding up dehydration. We statistically evaluated slice quality based on thickness, infrared power, and airflow. This assessment focused on drying time, color, shrinkage, water activity, and rehydration ratio. The onion slices were dried with infrared powers set at 1500, 3500, and 5500 W/m, airflow rates of 0.3, 0.7, and 1.0 m/s, and slice thicknesses of 4, 6, and 8 mm. We fitted the dehydrating curves from our experiments to thin-layer drying equations. The drying times required to lower the water content to approximately 6% (wb) were between 500-430, 460-400, and 420-350 min at infrared power levels of 1500-5500 W/m, respectively. Our calculations showed that the Midilli and Kucuk equation had the highest coefficient of determination ( ) and the lowest residual sum of squares ( ). The results revealed that drying time increased with higher airflow and slice thickness and decreased with greater intensity. The mean activation energy was 19-30 kJ/mol across the different conditions. The shrinkage ratio varied with airflow speed, and the rehydration ratio changed in response to increasing infrared radiation intensity and airflow. Furthermore, this research underscores the potential of advanced heating technologies to improve food drying processes, offering valuable insights for the food industry as it seeks optimization efficiency.