Question

Given below are two statements:
Statement (I): During manufacture of milk powder, concentration of soluble calcium and phosphate ions decreases and that of colloidal calcium phosphate increases.
Statement (II): Free fat levels are higher in whole milk powder manufactured by roller-dried process than that made by spray dried process.
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 compare drying methods:
- Roller-drying \(\rightarrow\) Severe heat, high free fat (membrane destroyed), lower solubility.
- Spray-drying \(\rightarrow\) Gentle heat, low free fat (membrane preserved), higher solubility.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Dehydrating milk to manufacture milk powder involves thermal processing, concentration, and drying.
These steps alter the physical state of milk lipids and shift the mineral equilibrium between the soluble and colloidal phases.

Step 2: Detailed Explanation:
Let us evaluate both statements:
-Statement (I): "During manufacture of milk powder, concentration of soluble calcium and phosphate ions decreases and that of colloidal calcium phosphate increases."
This statement is true.
In liquid milk, calcium and phosphate exist in equilibrium between a soluble phase in the serum and an insoluble colloidal phase inside the casein micelles (Colloidal Calcium Phosphate or CCP).
During thermal concentration and evaporation, the heating and removal of water shift this equilibrium.
Soluble calcium and phosphate ions associate to form additional colloidal calcium phosphate complexes, which associate with the casein micelles.
Thus, soluble mineral levels decrease while colloidal mineral levels increase.
-Statement (II): "Free fat levels are higher in whole milk powder manufactured by roller-dried process than that made by spray dried process."
This statement is true.
In the roller-drying (drum-drying) process, a thin film of milk is applied directly to the surface of rapidly rotating, steam-heated metal drums.
This subjects the milk to severe heat and mechanical shearing, which destroys the protective fat globule membrane.
As a result, the milk fat is released and exists as "free fat" on the surface of the powder particles.
In the spray-drying process, the milk is atomized into a chamber of hot air, which is a much gentler drying method.
Most of the fat globules remain intact and protected within the dried protein-lactose matrix, resulting in very low free fat levels.
Thus, both Statement (I) and Statement (II) are true.

Step 3: Final Answer:
Both Statement (I) and Statement (II) are true, which corresponds to Option (A).