Question

Lactose in milk occurs in form of

• A. True solution
• B. Colloidal dispersion
• C. Associated with milk proteins
• D. Suspension form

Hint:

Remember the physical states of milk components: - Fat $\rightarrow$ Emulsion - Casein $\rightarrow$ Colloidal dispersion - Lactose and whey proteins $\rightarrow$ True solution.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Milk is a complex multi-phase system where components exist in different physical states: emulsion (fat), colloidal dispersion (casein micelles), and true solution (soluble salts and lactose).

Step 2: Detailed Explanation:
Lactose (milk sugar) is a highly water-soluble disaccharide.
At normal milk temperatures, the concentration of lactose (about 8%) is well below its saturation limit in the aqueous phase of milk (the serum or whey).
Therefore, lactose molecules are completely dissolved and dispersed at a molecular level, existing in the state of a True solution.
In contrast, fat is present as an emulsion, caseins exist as a colloidal dispersion, and insoluble particles like soil or large protein aggregates would form a suspension.
Because dissolved lactose molecules do not scatter light or sediment under gravity, they follow the behavior of a true molecular solution.

Step 3: Final Answer
The correct option is (A).