Question

The fat globule size in milk ranges from

• A. 0.2 - 20 $\mu$m
• B. 20 - 200 nm
• C. 50 - 80 $\mu$m
• D. 0.2 - 20 nm

Hint:

Milk fat exists as an emulsion of globules with diameters ranging from 0.2 to 20 $\mu$m, with an average size of 3 to 4 $\mu$m. Homogenization reduces this average size to below 1 $\mu$m.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Milk fat is not dissolved in the aqueous phase of milk; instead, it exists as an oil-in-water emulsion.
The fat is distributed as spherical droplets or globules.
These globules are stabilized by a surrounding membrane known as the milk fat globule membrane (MFGM).
The size distribution of these fat globules is highly polydisperse and depends on the animal species, breed, lactation stage, and feed.

Step 2: Detailed Explanation:
In fresh, unhomogenized cow's milk, the diameter of the fat globules ranges from approximately 0.2 to 20 $\mu$m.
While the majority of the fat globules are small (less than 1 $\mu$m), they account for only a small fraction of the total fat volume.
Most of the milk fat volume is contained within larger globules with diameters between 3 and 4 $\mu$m.
Globules larger than 10 $\mu$m are relatively rare in normal milk but can occur in early lactation.
The options in nanometers (20 - 200 nm or 0.2 - 20 nm) are too small, corresponding to casein micelle or serum protein sizes.
The range of 50 - 80 $\mu$m is too large for stable emulsions, as such large droplets would rapidly coalesce and cream.
Therefore, the range of 0.2 - 20 $\mu$m is the correct physical size range.

Step 3: Final Answer
The size of fat globules in milk ranges from 0.2 to 20 $\mu$m.