Infrared drying characteristics and optimization of ginseng

Abstract

Fresh ginseng has a high moisture content and is easy to be deteriorated, thus an effective drying method is needed. Infrared drying is known as low energy consumption, and high heat transfer, thus the far infrared (FIR) and near infrared (NIR) drying characteristics of ginseng were investigated and compared. Influences of infrared temperature, radiation distance, and slice thickness on the drying kinetics, specific energy consumption, color change and rehydration ratio were analyzed. Results indicated that the drying rate of ginseng increased with increasing infrared temperature and decreasing radiation distance and slice thickness. The drying time under FIR was shortened by 33.3%, 25% and 20% at 40 °C, 50 °C, 60 °C compared to that under NIR, indicating that the drying efficiency of FIR was superior to that of NIR and with the decrease of temperature, this improvement became more obvious. The specific energy consumption can be reduced by up to 40% under FIR and the infrared drying was much more energy-efficient than hot air drying, with an energy reduction by up to 51.1%. Optimization of FIR drying showed that the optimal conditions were at a drying temperature of 50 °C, a slice thickness of 2 mm and a radiation distance of the 4th layer.