Assessment of the Effects of Drying Methods on the Drying Characteristics, Color, Nutritional and Medicinal Attributes of Dioscorea opposita Thunb

Dioscorea opposita is a typical medicine-food homologous herb.Its rhizomes are used in both cuisine and medicine.Drying treatments are considered to be the crucial step to preserve the nutritional and medicinal ingredients of D. opposita in the post-harvest processes.In this work, we conducted a comparative study to assess the impact of four different drying methods (room-temperature drying (RTD), sun drying (SD), hot-air drying (HAD) and freeze drying (FD)) on the drying characteristics, color, nutritional and medicinal attributes (contents of starch, soluble sugar, soluble protein, polysaccharides, diosgenin, allantoin and antioxidant capacity) of D. opposita.Results showed that HAD had a shorter drying time than others, as well as the highest soluble sugar content (66.20 mg/g), allantoin content (9.93 mg/g) and antioxidant capacity (12.31 mol/g).FD sample exhibited higher dry-to-fresh weight ratio (DFWR), higher starch content (687.94mg/g), soluble protein content (36.34 mg/g), polysaccharide content (35.32 mg/g) and diosgenin content (0.19 mg/g) than those dried with other methods.FD could improve the dominant color parameters of D. opposita with the highest white index (WI).Samples treated with FD had the highest comprehensive score (2.032) in the principal component analysis and hierarchical cluster analysis.While FD is recommended for optimal quality retention, HAD shows specific merits for targeted bioactive extraction, with additional advantages in energy efficiency and scalability.The findings provide a practical framework for method selection based on quality and cost-effectiveness.