Effects of traditional and emerging drying techniques on the microstructure and quality of Lycium barbarum L

Drying is the critical step in ensuring the postharvest storage and circulation of goji berries ( Lycium barbarum L). However, most previous research has focused on macroscopic quality, leaving a lack of systematic investigation into the effects of different drying techniques on quality and microstructural changes, which hinders the optimization of high-quality drying processes. This study systematically compared the effects of traditional drying techniques (sun drying, SD; hot-air drying, HD) and emerging drying techniques (microwave drying, MD; vacuum pulsation-drying, VPD; vacuum freeze-drying, VFD) on the microstructure, physicochemical properties, and bioactive compounds of goji berries. Results showed that VPD and VFD most effectively preserved structural integrity and bright red coloration, though some loss of water-soluble nutrients was observed (e.g., total sugar: 50.51 % in MD, compared with 36.14 % in VPD and 42.52 % in VFD). MD had the highest drying efficiency (460 min) and the greatest retention of total polyphenols (2.72 mg/g) and flavonoids (1.77 mg/g), but was associated with uneven drying and loose texture. Carotenoid composition revealed that HD samples had the highest total carotenoid content (714.37 μg/g), while VPD showed the best retention of zeaxanthin dipalmitate. FTIR and TG analyses indicated that drying techniques influenced carotenoid stability by altering hydrogen bonding and thermal stability. Overall, emerging drying techniques provided notable advantages in color retention, morphology, and characteristic compounds retention, but their industrial application requires further optimization to balance drying efficiency, nutrient retention, and energy consumption. • The zeaxanthin content in hot air drying was very higher than other drying techniques. • Microwave drying showed the highest drying efficiency and retention of polyphenols and flavonoids. • Goji berries dried under vacuum conditions had better overall properties.