Ultrasound-assisted chemical dewaxing synergistically coupled with rotary microwave vacuum drying for enhanced quality and bioactive retention of Lycium barbarum L

Wolfberries have attracted considerable attention due to their exceptional bioactive properties. However, their dense waxy cuticle and high moisture content often lead to color degradation and bioactive compound losses during conventional drying. To overcome this processing bottleneck, this study develops an integrated process combining ultrasound (US)-assisted chemical dewaxing pretreatment with rotary microwave vacuum drying. Six food-grade dewaxing agents (Na₂CO₃, NaHCO₃, C₆H₅Na₃O₇, C₆H₁₁NaO₇, NaCl, and C₂H₆O) were applied in conjunction with ultrasonic treatment, and their effects on drying performance and overall quality of wolfberries were systematically evaluated. The results demonstrate that ultrasound-assisted chemical dewaxing effectively disrupts the waxy cuticle and enhances cell wall permeability, thereby significantly shortening drying time while improving pigment stability and the retention of bioactive compounds. Among all treatments, wolfberries pretreated by US-Na₂CO₃ achieved the highest effective moisture diffusion coefficient of 2.93 × 10^-9 m²/s, accompanied by the lowest specific energy consumption of 95.36 kWh/kg. US-Na₂CO₃, US-NaHCO₃, and US-C₆H₅Na₃O₇ exhibited the most pronounced overall improvements, significantly outperforming standalone rotary microwave vacuum drying and natural drying in terms of polysaccharide, betaine, carotenoids, total flavonoid, and vitamin C retention, as well as antioxidant capacity. Correlation analysis reveals significant positive associations between major bioactive components and antioxidant inhibition rates, whereas ΔE is negatively correlated with bioactive compound retention, indicating a synergistic relationship between color stability and functional quality. Principal component analysis and comprehensive evaluation identify US-Na₂CO₃ as the optimal pretreatment, achieving the highest overall quality score (0.958) and yielding a uniform surface microstructure texture with naturally formed strip-like folds. Overall, this study provides critical process strategies and a robust theoretical basis for improving the quality and efficiency of wolfberry processing using rotary microwave vacuum drying.