Mechanistic Insights into Effect of Sugar Impregnation Pretreatment on Texture and Moisture Stability of Freeze-Dried Pear Slices

The product quality of freeze-dried pear slices is limited by moisture absorption, texture softening, and color deterioration. This study evaluated the effects of sugar impregnation using glucose, fructose, and sucrose at 2 M and 3 M concentrations on key quality attributes. Sugar impregnation improved the product’s appearance, texture, and flavor by reducing moisture absorption, reinforcing the cell wall, and forming a surface sugar layer, exceeding the benefits of osmotic dehydration. Among all groups, 3 M sucrose-treated samples exhibited the highest glass transition temperature (Tg), lowest moisture uptake, and most compact structure, indicating enhanced stability and reduced hygroscopicity. Further analyses revealed that sugar impregnation regulated microstructure and water-binding behavior, contributing to better physical properties. These findings suggest that high-concentration sucrose impregnation is an effective strategy to improve structural integrity and extend the shelf life of freeze-dried fruits and vegetables, offering promising applications in food preservation.