# Food Processing Unit Operations Questions and Answers – Mechanical Separation – Centrifugation

This set of Food Processing Unit Operations Multiple Choice Questions & Answers (MCQs) focuses on “Mechanical Separation – Centrifugation”.

1. What is the principle of centrifugation?
a) Sedimentation principle
b) Filtration principle
c) Evaporation principle
d) Size reduction principle

Explanation: Centrifuge works using the sedimentation principle, due to centrifugal acceleration denser substances move outward in the radial direction and that are less dense are displaced and move to the center.

2. What is called centrifugation?
a) Separated through spinning
b) Separate components at higher temperature
c) Separate components at lower temperature
d) Separated through evaporation

Explanation: Centrifugation is the process where a mixture is separated through spinning. It is used to separate skim milk from whole milk, washing machine and blood cells from your blood plasma.

3. Who invented centrifugation?
a) Newton
b) G.G. Stokes
c) Antonin Prandtl
d) Al-Kindi

Explanation: G.G. Stokes invented sedimentation. Newton discovered gravity. Antonin Prandtl invented centrifugation. Al-Kindi invented distillation.

4. What is use of density gradient centrifugation?
a) To purify viruses, ribosomes, membranes
b) Toremovedirt
c) To remove fine particles
d) To remove large particles

Explanation: Density gradient centrifugation is used to purify viruses, ribosomes, membranes. A sucrose density gradient is created by gently overlaying lower concentrations of sucrose on higher concentrations in centrifuge tubes where particles of interest are placed on top in ultracentrifuges. The particles move through the gradient until they reach the same sucrose density and fraction is removed and analyzed.

5. Which of the following statements about differential pelleting centrifugation are correct?
Statement 1: Tissue such as the liver is homogenized by this method.
Statement 2: The overlying solution is placed in another centrifuge tube for progressing steps.
a) True, False
b) True, True
c) False, True
d) False, False

Explanation: Differential pelleting centrifugation is the most common type of centrifugation used. Tissue like liver is homogenized.After sedimentation, the bottom is called pellet and an overlying solution called supernatant. The overlying solution is then placed in another centrifuge tube for progressing steps.

6. What is other name for zonal centrifugation?
a) Isopyniccentrifugation
d) Differential centrifugation

Explanation: Zonal centrifugation is also known as band or gradient centrifugation and relies on the concept of sedimentation coefficient. In this process, a density gradient is created in a test tube with sucrose and high density at the bottom.

7. Which centrifugation depends on buoyant densities?
a) Isopynic centrifugation
d) Differential centrifugation

Explanation: Isopynic centrifugation depends on buoyant densities, not on the velocities. CsCl, NaI gradients are the self-forming gradients for macromolecules and nucleotides under centrifugal force.

8. What are applications of centrifugation?
a) To separate two miscible substances and analyze the hydrodynamic properties of macromolecules
b) To separate two miscible substances and water treatment
c) Purification of mammalian cells and water treatment
d) Analyze the hydrodynamic properties of macromolecules and water treatment

Explanation: Applications of centrifugation are separation of two miscible substances, to analyze the hydrodynamic properties of macromolecules, purification of mammalian cells, separating chalk powder from water and removing fat from milk to produce skimmed milk.

9. Is centrifugation used in wine processing?
a) True
b) False

Explanation: Centrifugation is used in wine processing where the wine is clarified and stabilized by using centrifugation process.It is similar to sedimentation principle, where the centrifugal accelerates the denser substances to move outward in the radial direction and that are less dense are displaced and move to the center.

10. Which of the following statements about centrifugation are correct?
Statement 1: Particles are separated from a solution according to their size.
Statement 2: Particles are not separated from a solution according to their shape.
a) True, False
b) True, True
c) False, True
d) False, False

Explanation: Centrifugation is a process of separating substances which involves the centrifugal force. The particles are separated from a solution according to their size, shape, density, the viscosity of the medium and rotor speed.

Sanfoundry Global Education & Learning Series – Food Processing Unit Operations.

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