Effects of combined infrared and hot‐air drying on ginsenosides and sensory properties of ginseng root slices (Panax ginseng Meyer)

Abstract

The article investigates comparative experimental results and analysis of three drying stratagems, namely, infrared (IR), hot‐air (HA), and combination of IR and HA (IR‐HA), on the drying characteristics, ginsenosides, and sensory properties of ginseng root slices. The three drying tests were conducted at 50, 60, and 70°C, and the IR power was monitored and controlled by proportional‐integral‐derivation in LabView. The results indicated that IR‐HA drying, due to HA replaced IR after 25 min, had a lower drying rate compared to IR drying. However, the ginsenosides contents of dried ginseng root slices by IR‐HA were higher than that of samples dried by HA and IR. Notably, after IR‐HA drying at 50°C, the dried samples have highest ginsenosides contents (31.20 mg/g), low color difference (5.38 ± 1.19), high rehydration capacity (39.8 ± 5.9%), and hardness (62.8 ± 5.3 N), uniform and compact microstructure, and low energy consumption (5.65 ± 0.28 kwh/kg‐water). PRACTICAL APPLICATIONS: Ginseng roots have been widely used as therapeutic agents, dietary supplements, and healthy food. Drying is one of the common and traditional methods to prolong the shelf life of ginseng. Compared to hot‐air (HA) drying, infrared radiation (IR) drying has a few advantages, including greater energy efficiency, faster drying rate, and lower energy consumption. However, the undesirable drying temperature could lead to the charring of samples. The objectives of this study were to investigate the drying characteristics of ginseng slices with HA, IR, and hybrid (IR‐HA) drying, and compare the differences in ginsenosides, color, shrinkage ratio, rehydration, hardness, microstructure, and energy consumption by three drying stratagems. The results indicated that IR‐HA with drying temperature of 50°C is the optimum process for ginseng drying. The dried samples show short drying time, high ginsenosides contents and satisfactory apparent qualities in that condition.