Effect of ultrasonic-assisted hot-air drying on the quality and drying kinetics of Taraxacum mongolicum.

Drying of Taraxacum mongolicum Hand.-Mazz (TMHM) was an effective approach for preventing spoilage and extending shelf life. Ten drying methods were systematically evaluated, among which ultrasonic-assisted hot-air drying (Us-HA-D) was identified as the most suitable technique. The drying kinetics analysis indicated that the Weibull model could offer the best fit to the experimental data, while the drying curves revealed that Us-HA-D increased the drying rate by approximately 25-30% compared to the conventional hot-air drying, leading to a reduction in total drying time of up to 40.3%. The microstructural observations confirmed that ultrasonic pretreatment induced the formation of microchannels, which facilitated moisture migration and resulted in a 25.4% rise in the effective moisture diffusivity. Us-HA-D method also significantly improved color preservation, exhibiting the lower total color difference (ΔE), and optimally maintained bioactive components, with the retention of chicoric acid, chlorogenic acid, and the total phenolic content enhanced by 40.2%, 55.6%, and 40.3%, respectively. The process of Us-HA-D was optimized using the response surface methodology under the following conditions: ultrasound power of 535 W, ultrasound duration of 30 min, air temperature of 60°C, and air velocity of 3.8 m/s, achieving an optimal balance between the product quality and drying efficiency. The findings supported that Us-HA-D was a promising industrial-scale technology for producing high-quality dried TMHM with well-preserved phytochemical profile, color integrity, and antioxidant properties, highlighting its potential for broad application in the drying of other food materials.