Question

Which protein in cow milk has got an influence in creaming process

• A. Immunoglobulins
• B. Casein
• C. Alpha lactalbumin
• D. Beta Lactoglobulin

Hint:

Gravity creaming depends on fat globule clustering. Immunoglobulins (specifically cryoglobulins/IgM) act as natural cryo-agglutinins, clustering fat globules at cold temperatures to accelerate creaming.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Creaming is the physical process by which fat globules rise to the surface of milk under the influence of gravity, forming a cream layer.
The rate of creaming in raw, unhomogenized milk is much faster than predicted by Stokes' Law for individual fat globules. This is due to the clustering of fat globules into aggregates.

Step 2: Detailed Explanation:
The rapid clustering and creaming of fat globules in raw milk is facilitated by specific proteins acting as cold agglutinins:
- Immunoglobulins, particularly the high-molecular-weight immunoglobulin M (IgM) fraction, act as agglutinins in raw milk.
- When raw milk is cooled to temperatures below \(15\ ^{\circ}\text{C}\), these immunoglobulins adsorb onto the surface of fat globules.
- They facilitate cross-linking and aggregation among adjacent globules, forming large clusters.
- According to Stokes' Law, the velocity of rising particles is proportional to the square of their radius:
\[ v = \frac{2g r^2 (\rho_p - \rho_f)}{9 \eta} \]
- Because clustered fat globules have a much larger effective radius (\(r\)) than individual globules, they rise to the surface rapidly, speeding up the creaming process.
- This cryo-agglutination is inactivated by homogenization or high-heat pasteurization, which denatures the immunoglobulins.
- Other proteins (casein, \(\alpha\)-lactalbumin, \(\beta\)-lactoglobulin) do not possess this clustering capability.
Therefore, immunoglobulins are the proteins that influence the creaming process.

Step 3: Final Answer:
The milk protein that influences the creaming process is immunoglobulins.