Question

Given below are two statements, one is labelled as (A) and the other one is labelled as (B) as follows:
Statement (A): The heat stability of concentrated milk decreases considerably upon preheating of milk.
Statement (B): During preheating, most serum proteins are denatured and in the acid pH range they strongly aggregate thereby no age gelation occurs.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Statement A is true and statement B is false.
• B. Statement A is false and statement B is true.
• C. Both statements are false.
• D. Both statements are true.

Hint:

For dairy technology examinations, remember that preheating denatures whey proteins and alters interactions with casein micelles.
Do not assume that protein aggregation eliminates age gelation, as age gelation depends on several physicochemical factors besides protein denaturation.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Heat stability of concentrated milk is an important property in the manufacture of evaporated and sterilized milk products.
Preheating causes denaturation of whey (serum) proteins and promotes their interaction with casein micelles.
These changes significantly influence the stability of concentrated milk during subsequent heat treatment.

Step 2: Detailed Explanation:
Analysis of Statement (A):
Preheating results in denaturation of whey proteins and their interaction with casein micelles.
These structural changes generally reduce the heat stability of concentrated milk, particularly under conditions used in evaporation and sterilization.
Hence, Statement (A) is true.
Analysis of Statement (B):
Although serum proteins are indeed denatured during preheating, the conclusion given in the statement is incorrect.
Protein denaturation and aggregation are influenced by pH, but aggregation does not imply that age gelation is prevented.
In concentrated and sterilized milk, age gelation is a complex phenomenon involving protein interactions, proteolysis, and storage conditions.
Therefore, the statement that protein aggregation during preheating ensures that no age gelation occurs is incorrect.
Hence, Statement (B) is false.

Step 3: Final Answer:
Statement (A) is true, whereas Statement (B) is false.
Therefore, the correct answer is Option (A).