Which drying method involves freezing the material and then sublimating the moisture under reduced pressure?

Which drying method involves freezing the material and then sublimating the moisture under reduced pressure?

• A. Freeze-drying
• B. Air-drying
• C. Desiccant drying
• D. Glycerin treatment

Answer: (A)

Freeze-drying is the process that freezes the material and then removes moisture by sublimation under reduced pressure. By freezing first, all the moisture becomes ice, and under vacuum the ice converts directly to vapor without passing through a liquid phase. This preserves delicate shapes, colors, and textures because there’s little collapse or distortion from liquid water during drying. Other methods rely on evaporation at ambient conditions or moisture-absorbing environments, which can cause more shrinkage or uneven drying, and glycerin treatment, while great for flexibility, replaces water with glycerin rather than removing it by sublimation.

Freeze-drying is the process that freezes the material and then removes moisture by sublimation under reduced pressure. By freezing first, all the moisture becomes ice, and under vacuum the ice converts directly to vapor without passing through a liquid phase. This preserves delicate shapes, colors, and textures because there’s little collapse or distortion from liquid water during drying. Other methods rely on evaporation at ambient conditions or moisture-absorbing environments, which can cause more shrinkage or uneven drying, and glycerin treatment, while great for flexibility, replaces water with glycerin rather than removing it by sublimation.