Question

Milk powder is made from milk by drying in a:

• A. Rotary drier
• B. Spray drier
• C. Drum drier
• D. Spouted bed drier

Hint:

For any heat-sensitive liquid feeds (such as milk, pharmaceuticals, or enzymes), a spray dryer is almost always the preferred choice because of the short contact time and evaporative cooling effect.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks for the standard type of industrial dryer used to produce milk powder from liquid milk.
This is a standard application of drying equipment in chemical and food processing.

Step 2: Key Formula or Approach:
Milk is a heat-sensitive liquid containing dissolved solids, proteins, and fats.
To produce dry milk powder without thermal degradation, the liquid feed must be dried rapidly with a short exposure time at elevated temperatures.

Step 3: Detailed Explanation:

• Spray Drying Mechanism: In a spray dryer, the liquid feed is atomized into a fine mist of droplets using a nozzle or rotating disc.
These droplets are sprayed into a drying chamber where they contact a co-current or counter-current flow of hot gas.

• Rapid Heat Transfer: Because of the high surface-to-volume ratio of the fine droplets, moisture evaporates almost instantly.
This rapid evaporation keeps the particle temperature low due to evaporative cooling, preventing thermal damage to the proteins and nutrients in the milk.
The resulting product is a free-flowing powder with uniform particle size.

• Other Dryers:
Rotary dryers are used for coarse, free-flowing solid grains (such as minerals or sand) and are too harsh for liquids.
Drum dryers can be used for flaking but can cause localized overheating, which affects product solubility and flavor.
Spouted bed dryers are used for larger, irregular granules.


Step 4: Final Answer:
Milk powder is industrially produced from liquid milk using a spray dryer.