# Food Processing Unit Operations Questions and Answers – Size Reduction – Grinding Principles and Laws

This set of Basic Food Processing Unit Operations Questions and Answers focuses on “Size Reduction – Grinding Principles and Laws”.

1. What is the principle of particle size distribution?
a) Based on light scattering
b) Based on the pressure exerted by particles
c) Based on the pressure exerted by equipment
d) Based on the temperature exerted by particles

Explanation: The particle size distribution is based on the principle that when a ray of light is scattered by a set of particles, then the angle of scattering of light is indirectly proportional to the size of the particle.

2. What is Kick’s law?
a) Amount of energy required to tear the given material
b) Amount of energy required to crush the given material
c) Amount of energy required to compress the given material
d) Amount of energy required to break the given material

Explanation: The kick’s law is defined as the amount of energy required to crush a given amount of material to a specified fraction of its original size is the same, regardless of the original size.

3. What is Rittinger’s law?
a) Energy required is directly proportional to the increase in surface area
b) Energy required is indirectly proportional to the increase in surface area
c) Pressure required is directly proportional to the increase in surface area
d) Pressure required is indirectly proportional to the increase in surface area

Explanation: The Rittinger’s law is stated as the energy required for reduction in particle size of a solid is directly proportional to the increase in surface area.

4. What is Bond’s law?
a) Work required is directly proportional to the surface to volume ratio
b) Work required is indirectly proportional to the surface to volume ratio
c) Energy required is directly proportional to the surface to volume ratio
d) Energy required is directly proportional to the surface to volume ratio

Explanation: Bond’s law states that the work required to produce particles from large particle size is directly proportional to the square root of the surface-to-volume ratio.

5. Which of the following statements about crushing efficiency are correct?
Statement 1: It depends on surface energy created by energy.
Statement 2: Single layer particle crushing was taken to be 100% efficient.
a) True, False
b) True, True
c) False, True
d) False, False

Explanation: Crushing efficiency is defined as the ratio of surface energy created by crushing during crushing to the energy absorbed by the solid. Single layer particle crushing was taken to be 100% efficient.

6. Which of the following law determine energy requirement in size reduction?
a) Kick’s law, Bond’s law
b) Rittinger’s law, Bond’s law
c) Rittinger’s law and Kick’s law
d) Kick’s law, Bond’s law, Rittinger’s law

Explanation: Determination of energy required in size reduction is generally done using Kick’s law or Rittinger’s law. The Rittinger’s law is stated as the energy required for reduction in particle size of a solid is directly proportional to the increase in surface area. The kick’s law is defined as the amount of energy required to crush a given amount of material to a specified fraction of its original size is the same, regardless of the original size.

7. Which of the law is used for coarse grinding?
a) Rittinger’s Law
b) Kick’s Law
c) Bond’s Law
d) Bond’s Law, Rittinger’s Law, and Kick’s Law

Explanation: Kick’s law is used for coarse grinding when the size ratio of original material to end materials is 8:1. The kick’s law is defined as the amount of energy required to crush a given amount of material to a specified fraction of its original size is the same, regardless of the original size.

8. Which of the law is used for fine grinding?
a) Rittinger’s Law
b) Kick’s Law
c) Bond’s Law
d) Bond’s Law, Rittinger’s Law, and Kick’s Law

Explanation: Rittinger’s Law is defined as the energy required for reducing the size of the solid particle is directly proportional to the increase in surface area. Rittinger’s Law is used for fine grinding.

9. Which of the law is used for intermediate grinding?
a) Rittinger’s Law
b) Kick’s Law
c) Bond’s Law
d) Bond’s Law, Rittinger’s Law, and Kick’s Law

Explanation: Bond’s law is used for intermediate grinding. Bond’s law states that the work required to produce particles from large particle size is directly proportional to the square root of the surface-to-volume ratio.

10. Are size reduction results in loss of volatiles in heat sensitive foods?
a) True
b) False

Explanation: Size reduction causes loss of volatiles in heat sensitive foods like spices. In wheat milling, the proteins, vitamins and minerals and other important food components are lost due to separation of the bran and aleurone layer.

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