Drying Kinetics, Quality Attributes, Energy Consumption, and Moisture Migration Mechanisms of <scp> <i>Pueraria lobata</i> </scp> Slices During Combined Far‐Infrared and Hot Air Drying

ABSTRACT This study designed and developed a combined drying system integrating far‐infrared radiation and convective hot‐air heating, and employed this system to investigate the far‐infrared–hot‐air drying kinetics and quality attributes of Pueraria lobata (kudzu) slices of varying thicknesses (3, 4, and 5 mm) at temperatures of 50°C, 60°C, and 70°C. Experimental results indicate that the drying process of kudzu slices exhibited only a falling‐rate period without a constant‐rate period; drying time decreased with increasing temperature or decreasing slice thickness. The logarithmic model provided the most accurate description of the drying kinetics, demonstrating the highest R 2 and lowest χ 2 and RMSE values among the tested models. The effective moisture diffusivity ranged from 1.926 × 10 −8 to 5.173 × 10 −8 m 2 /s, and the activation energy was 19.264–24.314 kJ/mol. Samples dried at 50°C showed the smallest total color difference (Δ E ). Energy consumption decreased with increasing temperature or decreasing slice thickness. Slices with a thickness of 4 mm exhibited more stable dimensional characteristics. Optimal retention of total phenolics and total flavonoids was achieved at 60°C for 5‐mm slices and at 50°C for 5‐mm slices, respectively. Low‐field nuclear magnetic resonance (LF‐NMR) results revealed that free water was preferentially removed during drying, and bound water became the dominant residual water form over time. This study contributes to understanding the drying kinetics of kudzu slices and provides guidance for optimizing far‐infrared–hot‐air drying processes.