Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A) : Extruded feed manufacture, high temperature high moisture and high pressure are used.
Reason (R) : In extruded feed production, small air pockets are formed inside pellets and they float in the water.
In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Extrusion expansion is a direct thermodynamic result of flashing steam at the die exit due to high internal pressures and temperatures, which is what creates the air pockets needed for floating pellets.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Extrusion is a high-temperature short-time (HTST) physical process widely used in manufacturing commercial aquafeeds.
This technology allows the production of both floating and sinking pellets by manipulating moisture, temperature, and pressure during the manufacturing process.

Step 2: Detailed Explanation:
The process of feed extrusion utilizes a combination of high moisture (usually 20--30%), high temperature (100--140 \(^\circ\)C), and high pressure inside the extruder barrel.
These conditions are essential to cook the ingredients, gelatinize the starches, and texturize the proteins.
As the cooked feed mixture is pushed through the extruder die, it experiences a sudden and extreme drop in pressure to atmospheric levels.
This abrupt pressure drop causes superheated water inside the feed matrix to rapidly flash into steam, expanding the pellet.
This expansion creates a highly porous structure with numerous tiny air pockets trapped inside the pellet.
These air pockets significantly reduce the density of the pellet below that of water, allowing it to float.
Therefore, the high temperature, moisture, and pressure are the directly responsible physical conditions for the creation of these air pockets.
Thus, both Assertion (A) and Reason (R) are correct, and Reason (R) provides the direct scientific explanation for why these extrusion conditions are used.

Step 4: Final Answer:
Both (A) and (R) are true, and (R) is the correct explanation of (A).