Physical State of Lactose and Ash in Milk

Lactose & ash present in milk as:

Correct Answer: True Solution

Both Lactose (milk sugar) and Ash (minerals/salts) are present in milk as a True Solution — they are completely dissolved in the aqueous phase of milk at molecular or ionic level.

Physical States of Milk Constituents

• Fat: Emulsion (fat-in-water type O/W emulsion)
• Casein protein: Colloidal suspension (as calcium-caseinate-phosphate complex)
• Whey proteins (α-lactalbumin, β-lactoglobulin): Colloidal solution
• Lactose & Ash: True solution ✔

Significance of True Solution Form

Because lactose and minerals are in true solution, they are osmotically active and are primarily responsible for depressing the freezing point of milk below 0°C. Specifically, lactose and chloride are the main contributors to freezing point depression (FPD).

Why Other Options Are Wrong

• Emulsion → for fat.
• Suspension → for casein (colloidal suspension).
• Colloidal suspension → for casein protein specifically.