Optimization of Scutellaria baicalensis Drying Using Combined Ultrasound and Vacuum Far-Infrared Technology: Drying Kinetics and Bioactive Preservation

To address the thermal degradation and efficiency limitations of traditional drying methods on the active compounds of Scutellaria baicalensis, a novel drying technique combining ultrasonic pretreatment with vacuum far-infrared drying (US-VFIRD) was developed. The ultrasonic cavitation effect (power: 40-80 W, frequency: 20-60 kHz, time: 10-30 min) was employed to disrupt the hydrogen bond network of the cell wall, promoting the release of bound water and reducing mass transfer resistance. This was subsequently coupled with vacuum far-infrared drying (50°C, -20 kPa), which created a mild thermal environment to inhibit the degradation of heat-sensitive components. The results demonstrated that this synergistic approach significantly optimized the drying kinetics, with the peak drying rate of the 60 W/40 kHz/20 min group reaching 0.02853 g/(g·min), a 30% increase compared to the untreated group. The XGBoost multi-objective model (R² > 0.99, MSE = 0.00013) was used to quantify the effects of ultrasonic parameters on water migration, revealing that the interaction between power and frequency was the dominant influencing factor. Quality analysis indicated that the 60 W/40 kHz/30 min group exhibited the highest total flavonoid retention rate (218.7 mg/g), with total phenolic content increasing by 34.2% and antioxidant activity improving by 46.00%. These improvements were attributed to the preservation of cell microstructure (confirmed by SEM) and minimized thermal damage. This integrated technology not only enhances energy efficiency (COPd up to 0.0144) but also ensures quality retention, providing valuable theoretical support for the high-quality and efficient processing of Scutellaria baicalensis.