Question

Given below are two statements:
Statement (I) : Ash represents the true salt composition of milk.
Statement (II) : Salt balance of milk is a ratio between cations (Calcium and Magnesium) and anions (Citrate and Phosphate).
In light of the above statements, choose the most appropriate answer from the options given below.

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

Hint:

To remember the salt balance ratio, place the positively charged divalent metal ions (Cations: $\text{Ca}^{2+}$, $\text{Mg}^{2+}$) in the numerator, and the negatively charged organic/inorganic acid ions (Anions: Citrate, Phosphate) in the denominator.
This ratio must be close to its optimal range to prevent coagulation of milk during heat processing.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The minerals in milk exist as dissolved ions, colloidal salts, and organic complexes.
Understanding the difference between the analytical ash content and the actual mineral salts present in liquid milk is essential for dairy chemistry.

Step 2: Detailed Explanation:
Let us analyze Statement (I): "Ash represents the true salt composition of milk."
This statement is incorrect.
The ash content of milk is determined by heating a sample to high temperatures ($550^\circ$ C to $600^\circ$ C) in a muffle furnace to burn off all organic matter.
This high-heat process causes several chemical changes in the milk minerals:
- Organic salts (such as citrates) are oxidized and lost as carbon dioxide.
- Phosphorus and sulfur present in milk proteins (such as casein) and lipids are oxidized into inorganic phosphates and sulfates, which remain in the ash.
- Volatile minerals, including sodium, potassium, and chloride, can be partially lost through volatilization.
Consequently, the composition of the resulting ash does not match the actual salt and mineral profile of the original liquid milk.
Now let us analyze Statement (II): "Salt balance of milk is a ratio between cations (Calcium and Magnesium) and anions (Citrate and Phosphate)"
This statement is correct.
The salt balance in milk is defined by the ratio of divalent cations to multivalent anions, typically expressed as:
\[ \text{Salt Balance Ratio} = \frac{[\text{Ca}^{2+}] + [\text{Mg}^{2+}]}{[\text{Citrate}^{3-}] + [\text{Phosphate}^{3-}]} \] This ionic balance is critical to the stability of casein micelles.
An imbalance in this ratio can cause milk proteins to destabilize and coagulate, especially during high-temperature treatments like sterilization or UHT processing.

Step 3: Final Answer:
Statement (I) is false, but Statement (II) is true.