Drying Kinetics and Energy Consumption of Astragalus Membranaceus Under Infrared Drying

Abstract

The Astragalus membranaceus (AM) slices was dried using three infrared drying techniques, including near-infrared drying (NIR), mid-infrared drying (MIR), and far-infrared drying (FIR). Studies and discussions about the impacts of infrared temperature, power, slice thickness, and wavelength on the drying properties, energy consumption, and associated performance were conducted. Results showed that the drying rate increased with increasing infrared temperature and wavelength, and with decreasing slice thickness, whereas the drying process was not significantly influenced by the infrared power. The drying efficiency of FIR was superior to that of NIR, and with the increase in temperature, this improvement became more obvious. FIR drying was the fastest with the least energy consumption among the three drying methods. Rehydration ratio and color change of AM slices were proportional to infrared temperature and wavelength, but inversely proportional to slice thickness. The effective moisture diffusion coefficients of AM slices under NIR and FIR drying ranged from 0.49244 × 10−9 to 1.16352 × 10−9 m2/s and 1.00432 × 10−9 to 2.51135 × 10−9 m2/s, respectively.