ultrasound led to a higher glass transition temperature,
lower water activity, moisture content and rehydration rate, severer structure collapse, less cavities and calcium uptake than PV did. Different
osmoconcentration pretreatment had no significant (P < 0.05) effect on the hardness, crispness, shrinkage and rehydration rate. Compared to
hot-air drying, freeze-dried apples showed the porous structure, minimal shrinkage, softer texture, better rehydration capacity, lighter color,
and slightly lower glass transition temperature.