Question

Given below are two statements:
Statement (I): Reduction of pH during spoilage reduces water holding capacity of proteins
Statement (II): pH does not have any role in changes occurring in properties of proteins and enzymes

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

The water-holding capacity of muscle proteins is lowest at their isoelectric point (pI), where the net charge on the proteins is zero.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Post-mortem anaerobic glycolysis leads to the accumulation of lactic acid, which lowers the pH of fish muscle.
This pH change has a significant impact on myofibrillar proteins and enzymes.

Step 2: Detailed Explanation:
Statement (I) is correct: A decline in pH towards the isoelectric point (pI) of myofibrillar proteins (approximately \(5.0 - 5.5\)) reduces their net charge.
This decrease in charge reduces the electrostatic repulsion between muscle filaments, causing the protein structure to contract and lowering its water-holding capacity (WHC).
Statement (II) is incorrect: pH is a key factor that influences protein conformation, solubility, denaturation, and enzymatic activity by changing the ionization state of amino acid side chains.

Step 3: Final Answer:
Therefore, Statement (I) is correct but Statement (II) is incorrect.