Influence of Electrohydrodynamics (EHD) on the Drying Characteristics and Active Ingredients of Astragalus Membranaceus Slices
Lan Ni, Yong-Ping Wang, Jingcheng Zhu
Abstract
This study compared needle-plate electrohydrodynamic drying (EHD) at 20, 25, and 30 kV to natural drying (ND) of Astragalus membranaceus slices, analyzing drying characteristics, quality, and mechanisms. Discharge diagnostics revealed filamentous discharge, with reactive nitrogen/oxygen species concentration and ion wind speed increasing with voltage. Within the 20-30 kV range, drying rate and effective moisture diffusivity significantly increased with electric field strength. At 30 kV, drying rate was 1.73 times ND's, and diffusivity was 5.1 times higher. Quality was optimal at 25 kV: rehydration rate was 1.18 times ND's; calycosin and astragaloside IV contents were 1.38 and 1.14 times ND's, respectively; shrinkage was reduced to 0.68 times ND's; and browning was significantly inhibited (BI = 0.46 times ND's), yielding the color closest to fresh samples. Polysaccharide content was slightly lower (0.97 times ND's). In summary, EHD, particularly at 25 kV, markedly enhances drying efficiency and improves key quality attributes (rehydration, bioactive compound retention, color, reduced shrinkage), despite a minor negative effect on polysaccharides. This work clarifies the EHD mechanism and supports its application in drying traditional Chinese medicines.