Characterization and quality assessment of Astragalus slices dried using plasma synergistic technology

Plasma drying, as a non-thermal food drying technology, has received widespread attention due to its lower energy consumption and better quality of dried products compared with traditional thermal drying technology. To enhance the drying rate, this study incorporated crossflow and hot airflow to facilitate drying in conjunction with plasma treatment. These methods were termed convection-plasma synergistic drying (CPD) and hot air-plasma synergistic drying (HAPD). The dried Astragalus slices obtained from CPD and HAPD were compared with samples dried by plasma drying (PD), hot air drying (HAD), and natural drying (ND). The findings revealed that plasma synergistic drying reduced the drying duration by 41.67% and 25%, respectively, compared to PD. Notably, the shrinkage of Astragalus slices after PD was minimal, registering 31.79% and 22.44% lower rates than those observed for ND and HAD, respectively. After HAPD, the rehydration ratio of the Astragalus slices reached its peak, exceeding those of ND and HAD by 30.57% and 32.89%, respectively. Astragalus exhibited a loose and porous structure after plasma intervention, contrasting with surface collapses observed post-HAD and surface cracks evident after ND. The study noted a significant increase in astragaloside content after CPD, surpassing that of ND and HAD by 23.43% and 67.78%, respectively. Similarly, the mullein isoflavones content peaked after PD, measuring 29.89% and 28.02% higher than that of ND and HAD, respectively. Additionally, the study explored the internal water migration mechanism of Astragalus slices during the drying process using LF-NMR analysis.