Question

Freeze drying is also called _______

• A. Tray
• B. Drum
• C. Spray
• D. Sublimation

Hint:

Freeze drying is also called lyophilization or sublimation drying because frozen water is removed directly as vapour under vacuum.

Answer 1

The Correct Option is D

Concept:
Freeze drying is a drying method used for heat-sensitive pharmaceutical and biological products. It is also known as lyophilization.

Step 1: Principle of freeze drying.
In freeze drying, the product is first frozen. After freezing, water present in the product is removed under vacuum.

Step 2: Meaning of sublimation.
Sublimation is the direct conversion of ice into vapour without passing through the liquid state. \[ \text{Ice} \longrightarrow \text{Water vapour} \]

Step 3: Why it is called sublimation drying.
Since freeze drying removes water from the frozen state directly as vapour, the process is based on sublimation. Therefore, freeze drying is also called sublimation drying.

Step 4: Checking other options.
Tray drying, drum drying, and spray drying are different drying methods and do not represent the basic principle of freeze drying.

Step 5: Final answer.
Hence, freeze drying is also called sublimation drying. \[ \boxed{\text{Sublimation}} \]