Question

In the manufacture of floating extruded feeds, which of the following conditions are required?

• A. High pressure, low temperature and high moisture
• B. High moisture, high temperature and low pressure
• C. High temperature, high pressure and high moisture
• D. Low pressure, high temperature and low moisture

Hint:

Extrusion Cooking Conditions: Floating Aquafeeds require HIGH TEMPERATURE + HIGH PRESSURE + HIGH MOISTURE to gelatinize starch and cause flash expansion.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Extrusion technology in aquafeed manufacturing: high moisture conditioning combined with high temperature and pressure in the extruder barrel gelatinizes starch, creating vapor-expansion bubbles that confer low density and floating stability.
Key Formula or Approach:
\[ \text{Extruder Barrel: } \text{High Moisture } (20 - 30\%) + \text{High Temp } (120 - 160^\circ\text{C}) + \text{High Pressure } (30 - 50\text{ bar}) \xrightarrow{\text{Die Exit}} \text{Flash Expansion (Floating Pellet)} \]

Step 2: Detailed Explanation:
In aquafeed manufacturing and extrusion technology:
- Floating Extruded Fish Feeds are manufactured using specialized single- or twin-screw extruders operating under High Temperature, High Pressure, and High Moisture:
1. High Moisture ($20 - 30\%$): Added as steam/water in the pre-conditioner to plasticize the dough.
2. High Temperature ($120^\circ - 160^\circ ext{C}$): Thermally gelatinizes $> 90\%$ of dietary starches.
3. High Pressure ($30 - 60\text{ bar}$): Generated by the rotating screw against the die plate.
- As the molten mass exits the extruder die into ambient atmospheric pressure, superheated water instantly flashes into steam, creating a cellular microporous honeycomb matrix that reduces pellet density below water ($ ext{density} < 1.0 ext{ g/cm}^3$), causing the pellets to float.

Step 3: Final Answer:
Hence, the required conditions are High temperature, high pressure and high moisture, corresponding to option (C).