Question

Drum dryer is suitable for drying of
(A). Pulses
(B). Fruit puree
(C). Concentrated milk
(D). Leafy vegetables

Choose the correct answer from the options given below:

• A. (B), (C) and (D) only.
• B. (A), (B), (C) and (D).
• C. (A) and (C) only.
• D. (B) and (C) only.

Hint:

Remember: Drum dryers are strictly meant for liquid feeds, slurries, purees, or pastes.
They are never used for solid particulates or whole agricultural crops.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Drum drying (roller drying) is a continuous contact-drying method where a thin film of liquid, slurry, or paste is applied to the outer surface of a rotating, steam-heated metal drum.

Step 3: Detailed Explanation:
Let us evaluate the suitability of drum dryers for the given food items:
1.

Pulses (A): These are particulate solid grains, which cannot form a uniform liquid film on a drum. They are dried using fluid bed or bin dryers.
2.

Fruit puree (B): Slurries and viscous purees easily spread into a thin film on the hot drum surface, drying rapidly into a sheet that is scraped off by a doctor blade. Thus, (B) is suitable.
3.

Concentrated milk (C): Liquid concentrates can be rolled onto the drum to produce milk powder. Thus, (C) is suitable.
4.

Leafy vegetables (D): Solid leafy materials cannot be drum-dried; they are processed using tray or conveyor belt dryers.
Therefore, drum dryers are suitable only for (B) and (C).

Step 4: Final Answer:
The correct option is 4, which corresponds to (B) and (C) only.