Effect of Composite Restructuring on Drying Efficiency and Quality of Vacuum Freeze-Dried Dangshan Pear Slices

To investigate the effect of composite restructuring on the drying characteristics and quality of vacuum freeze-dried Dangshan pear slices, this study analyzed the chemical composition, microstructure, drying characteristics, thermal properties, basic quality, nutritional components, and flavor profiles of vacuum freeze-dried restructured Dangshan pear slices with lily bulb, Chinese yam and white jelly fungus and with none of them added (control). The results indicated that compared with the control group, the incorporation of these ingredients significantly prolonged the drying time and reduced the drying rate, extending the total vacuum freeze drying time by over 40%. Meanwhile, this incorporation increased the contents of starch, protein, and soluble sugars (including fructose, glucose, sorbitol, and sucrose) by 69.59, 1.14, and 266.07 mg/g, respectively, significantly elevated the glass transition temperature (T_g), caused a shift of the freezing phase change temperature range toward lower temperatures, and increased the endothermic enthalpy. The resulting product exhibited a more regular honeycomb-like porous microstructure, higher hardness and crispness, and reduced breakage rate during oscillation. The total phenolic and total flavonoid contents increased by 0.4 and 0.63 mg/g compared with the control group, respectively, and the antioxidant activity was stronger. Furthermore, significant differences (P < 0.05) in flavor characteristics were observed, with the composite restructured slices showing notably higher levels of bitter compounds. This study demonstrates that composite restructuring effectively enhances the nutritional value, texture, and flavor, thereby improving the overall quality of Dangshan pear slices. This provides a theoretical reference and technical support for applying this technique in fruit and vegetable processing. However, it prolongs the vacuum freeze-drying time, indicating a need for pretreatment techniques to improve the drying efficiency and promote its practical application.