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Food Science and Technology QUESTION #5992
Question 1
The 'de Laval' principle in centrifugal cream separation works because:
  • Cream is denser than skim milk and settles at the bottom of the centrifuge
  • Fat globules (\(\rho \approx 0.9\text{–}0.93\;\text{g/mL}\)) are less dense than the aqueous milk phase (\(\rho \approx 1.036\;\text{g/mL}\)); centrifugal force (\(3{,}000\text{–}7{,}000 \times g\)) causes fat globules to migrate toward the rotation axis while denser skim milk migrates outward✔️
  • Proteins are selectively removed by centrifugal force leaving fat behind
  • Skim milk freezes faster than cream at centrifuge temperatures
Correct Answer Explanation
In a centrifugal cream separator, rotation at \(6{,}000\text{–}8{,}000\;\text{rpm}\) generates centrifugal force (\(3{,}000\text{–}7{,}000 \times g\)). Fat globules (\(\rho \approx 0.9\text{–}0.93\;\text{g/mL}\)) migrate toward the rotation axis; skim milk (\(\rho \approx 1.036\;\text{g/mL}\)) migrates outward. The process is continuous — cream and skim milk exit through separate outlets.