Question

Puffed rice products are produced from parboiled and cooked rice by drying up to moisture content

• A. 4%
• B. 8%
• C. 12%
• D. 30%

Hint:

The critical moisture range for puffing most cereals (like rice or corn) is 11--13% (nominally 12%).
This level provides the perfect balance of steam pressure and structural strength for maximum expansion.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Puffing is a traditional thermal processing method that expands cereal starch granules through the rapid vaporization of internal moisture.
To achieve maximum expansion volume and a crisp texture, the rice grains must have a precise, optimal moisture content before being subjected to high-temperature puffing.

Step 2: Detailed Explanation:
The production of puffed rice involves parboiling, cooking, and conditioning the rice grains.
During parboiling, the starch undergoes complete gelatinization.
The cooked grains are then dried to an optimal, critical moisture content of approximately 11% to 13% (with 12% being the standard specification).
This specific moisture level is crucial for the puffing process:
- If the moisture content is too high (e.g., above 15--20%), the grains remain soft and do not build up the necessary internal steam pressure during rapid heating.
- If the moisture content is too low (e.g., below 8%), there is not enough water to generate the steam volume required to expand the rigid starch matrix.
- At around 12% moisture, the superheated water vaporizes rapidly during sand-roasting (at 200--250\(^\circ\)C), causing the gelatinized starch to expand into a highly porous, crisp puffed rice product.
Therefore, 12% is the correct moisture content.

Step 3: Final Answer:
For successful puffing, parboiled and cooked rice is dried to an optimal moisture content of 12%.