Question

When rice is cooked with water, the starch granules inside it absorb water and swell up, causing a change in texture and colour. This process is called:

• A. Dexterization
• B. Gelatinization
• C. Adsorption
• D. Parboiling

Hint:

Gelatinization requires both heat and moisture. Each starch source has a specific temperature range at which gelatinization occurs (typically between \(60^\circ\text{C}\) and \(85^\circ\text{C}\)).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Starch is a polysaccharide composed of amylose and amylopectin molecules packed tightly into crystalline granules.
When subjected to heat in the presence of water, these granules undergo a fundamental physical transition that alters their structure.

Step 2: Detailed Explanation:
During the cooking of raw rice, water molecules penetrate the starch granules.
As the temperature rises, hydrogen bonds holding the amylose and amylopectin chains together are disrupted.
This allows water to bind to the exposed hydroxyl groups of the starch molecules, causing the granules to absorb water and swell significantly.
As swelling continues, amylose molecules leach out into the surrounding water, and the crystalline structure of the granule is permanently lost.
This irreversible process is known as gelatinization.
It causes the mixture to thicken, transition from an opaque white to a translucent state, and become soft and digestible.
Let us clarify the other terms:
- Dextrinization (misspelled as Dexterization) is the dry-heat breakdown of starch into smaller, sweeter dextrin molecules.
- Adsorption is a surface phenomenon where molecules adhere to a surface.
- Parboiling is an industrial hydro-thermal processing of paddy prior to milling, which includes soaking, steaming, and drying steps.

Step 3: Final Answer:
The absorption of water and swelling of starch granules during wet-heat cooking is called gelatinization.