Cream is separated from milk during churning due to

The correct answer is centrifugal force.

Key Points

• Centrifugal force
  • Cream is separated from milk during churning primarily due to centrifugal force.
  • Churning involves rotating the milk at high speeds, causing denser components (like skim milk) to move outward.
  • Lighter fat globules (cream) cluster together and separate from the liquid due to this outward force.
  • This process mimics industrial centrifugal separators used in dairy production.
  • Centrifugal force is a pseudo-force that appears in rotating frames of reference.
  • Unlike gravity, it efficiently separates immiscible liquids of different densities.
  • Traditional churning uses this principle by agitating milk until fat coalesces into butter or cream.
• Gravitational Force
  • Gravity acts downward but is too weak alone to separate cream efficiently.
  • Cream naturally rises over time due to density differences, but this is slow (taking hours or days).
  • Industrial separation relies on centrifugal force to accelerate this process.
  • Gravity's role is minimal in mechanical churning or centrifugation.
  • Sedimentation due to gravity is impractical for large-scale dairy processing.
  • Centrifugal force in machines provides faster, more controlled separation.
  • Thus, gravity is not the primary force in churning.
• Frictional Force
  • Friction occurs between milk particles and container walls during churning.
  • However, it does not directly contribute to cream separation.
  • Frictional heat may slightly affect viscosity but doesn't aid in fat globule clustering.
  • The key separation mechanism is density-based, not friction-dependent.
  • In butter-making, friction helps clump fat after separation, but not in initial cream extraction.
  • Industrial separators minimize friction to allow smooth rotation.
  • Thus, frictional force is irrelevant to the core separation process.
• Centripetal Force
  • Centripetal force acts inward, keeping milk particles in circular motion during churning.
  • It is the real force (provided by container walls) that enables rotation.
  • However, it does not cause separation—centrifugal force (outward effect) does.
  • Separation occurs because denser components resist motion more, moving outward.
  • Centripetal force is necessary for rotation but not the direct cause of cream separation.