Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Casein curd is precipitated at temperatures between 35 and 38°C.
Reason (R): Curd precipitated at temperature below 35°C has a texture resembling chewing gum, being stringy, lumpy and coarse whereas, curd precipitated at about 43°C is very soft and fine.
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:

- Low precipitation temperature (\(< 30^{\circ}\text{C}\)) = Fine, soft, dusty curd (hard to drain).
- High precipitation temperature (\(> 40^{\circ}\text{C}\)) = Plastic, rubbery, sticky curd (chewing-gum texture).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Industrial casein is manufactured by acidifying skim milk to its isoelectric point (pH 4.6), causing the casein micelles to destabilize and precipitate out of solution.
The temperature during this precipitation step determines the physical structure, handleability, and washing efficiency of the resulting curd.
Detailed Explanation:
Let us evaluate the Assertion and Reason statements:
- Assertion (A): The optimal temperature range for precipitating acid casein curd is between \(35^{\circ}\text{C}\) and \(38^{\circ}\text{C}\).
This temperature range produces a firm, cohesive, and granular curd that is easy to wash, drain, and press without losing too many fine particles in the whey.
Therefore, Assertion (A) is true.
- Reason (R): The physical behavior of the curd changes at temperatures outside this optimal range:
1. If the temperature is too low (below \(35^{\circ}\text{C}\)), the curd is very soft, fine, and friable, making it difficult to wash and dewater.
2. If the temperature is too high (above \(43^{\circ}\text{C}\)), the curd particles become highly sticky, cohesive, and rubbery, resembling chewing gum. This lumpy, stringy structure makes it difficult to wash out whey proteins and salts.
The Reason statement describes these two behaviors backwards.
Therefore, Reason (R) is false.

Step 2: Final Answer:
The Assertion (A) is true, but the Reason (R) is false.