Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A) : Large amount of sucrose present in sweetened condensed milk causes a defect called 'sandiness'.
Reason (R) : \(\alpha\)-Lactose hydrate crystals in sweetened condensed are hard and not very soluble, and they feel gritty when placed in mouth, similar to sand particles. Hence, this defect is called 'sandiness'.
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:

To prevent the sandiness defect in sweetened condensed milk:
Practice "forced crystallization" by seeding the concentrated milk with extremely fine lactose crystal dust ($<10\,\mu\text{m}$) at $30^\circ$ C to $38^\circ$ C.
This encourages the formation of millions of tiny crystals instead of a few large, gritty ones.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Sweetened condensed milk is a concentrated dairy product preserved by adding sucrose to lower its water activity.
Due to the high concentration of milk solids and sugar, crystallization of lactose must be carefully controlled to maintain a smooth, creamy texture.

Step 2: Detailed Explanation:
Let us analyze Assertion (A):
The assertion states that a large amount of sucrose causes the defect called 'sandiness'.
This statement is incorrect.
The 'sandiness' defect in sweetened condensed milk is caused by the crystallization of lactose (specifically \(\alpha$-lactose monohydrate), not sucrose. While sucrose is present in high amounts, it remains in solution unless the product is severely dehydrated, which would cause a different defect known as sugar sedimentation. Now let us analyze Reason (R): The reason states that \(\alpha\)-lactose hydrate crystals are hard, relatively insoluble, and feel gritty like sand in the mouth, which is why the defect is called sandiness.
This statement is correct.
Sweetened condensed milk contains more lactose than can remain dissolved at room temperature, making it supersaturated.
During cooling, lactose tends to crystallize.
If these crystals grow larger than 10 to 12 microns in size, they can be felt on the tongue, creating a gritty or "sandy" texture.
To prevent this defect, the milk is seeded with fine lactose powder during cooling to promote the formation of many small crystals (under 10 microns) that cannot be detected by the palate, ensuring a smooth texture.
Since Assertion (A) is false but Reason (R) is true, the correct option is (D).

Step 3: Final Answer:
Assertion (A) is false, but Reason (R) is true.