Question

Process of parboiling reduces breakage during milling due to -

• A. Migration of oil into the bran layers
• B. Improved opacity of rice kernel
• C. Softening and loosening of rice husk
• D. Gelatinization of starch

Hint:

Parboiling also causes water-soluble vitamins (like Thiamine) to migrate from the bran into the endosperm, which significantly increases the nutritional value of polished parboiled rice.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Parboiling is a hydrothermal treatment process applied to paddy (rice) before milling. It consists of three sequential steps: soaking, steaming, and drying.

Step 2: Detailed Explanation:
Let us analyze the chemical and physical changes that occur during parboiling:

Rice endosperm consists primarily of starch granules held together in a crystalline matrix.

Raw rice often contains internal micro-fissures and cracks caused by rapid drying or environmental stress in the field. During mechanical milling, these weak points cause the grains to break easily, resulting in a high percentage of broken rice and low head rice yield.

During the soaking and steaming stages of parboiling, moisture and high-temperature steam enter the kernel, causing the starch granules to absorb water, swell, and undergogelatinization.

This gelatinized starch flows into the micro-cracks and voids within the endosperm, cementing the grain structure back together as it cools and dries.

The starch changes from a crystalline structure to a tough, amorphous, glassy state.

This structural change makes the rice kernel much harder, tougher, and highly resistant to mechanical shear and impact forces during milling, thereby significantly reducing grain breakage.
Therefore, gelatinization of starch is the primary physical mechanism that prevents breakage.

Step 3: Final Answer:
The correct option is (D), representing Gelatinization of starch.