Drying of Schisandra chinensis: Process Engineering, Kinetics, Quality Evolution, and Scale-Up Challenges

Schisandra chinensis is a high-value medicinal and edible fruit rich in lignans, polysaccharides, oligosaccharides, organic acids, and volatile compounds. Drying is an essential postharvest processing step for extending shelf life and stabilizing quality due to the high-moisture content and rapid postharvest deterioration of fresh fruits. This review critically evaluates drying strategies for S. chinensis, including conventional (shade and sun-drying), thermal (hot air, infrared, and heat pump drying), vacuum freeze-drying, microwave drying, and pretreatment-assisted approaches by integrating processing performance and quality evolution, with emphasis on drying kinetics, energy demand, shrinkage, and changes in major quality-related compounds. Current evidence supports hot-air drying as the most established scalable option, whereas vacuum freeze-drying improves retention of selected heat-sensitive constituents at greater complexity and cost. Microwave and pretreatment-assisted strategies show potential, while infrared and heat pump drying require further validation for S. chinensis. Critically, effective moisture diffusivity and energy data for intact fruits remain scarce, and constant geometry diffusion models may be biased by shrinkage. Future studies should integrate kinetics, energy, water activity and microbial safety, multi-component quality, and pilot-scale validation using standardized reporting.