Food Engineering Multiple Choice Questions on “Unit Operations – Size Reduction and Seperation-1”.
1. Which of the following is an advantage of size reduction?
a) Enhanced heat/mass transfer
b) Intimate contact with certain food items
c) Enhanced heat/mass transfer & intimate contact with certain food items
d) None of the mentioned
Answer: c
Clarification: Increased surface area due to size reduction enhances heat/mass transfer. Small sized particles have more intimate contact with certain food items.
2. Statement 1: Dispersion of one immiscible liquid into another also involves size reduction.
Statement 2: Leaching requires size reduction.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: Dispersion of one immiscible liquid into another also involves size reduction so that they mix well. Leaching requires size reduction as it is desirable to access the interior parts of the particles which are enhanced by reducing the size of the particles.
3. Which of the following is NOT true with respect to size reduction?
a) Size reduction is an energy inefficient process as the energy required for grinding is very high
b) Some of the energy liberated in the formation of new small surfaces is the grinding energy required by food material per unit surface area to form new surface areas and the rest is generally just heat
c) The crushing efficiency is inversely proportional to the surface created
d) None of the mentioned
Answer: c
Clarification: The crushing efficiency is directly proportional to the surface created
4. Which of the following is NOT a method used for size reduction?
a) Cutting
b) Impact
c) Burning
d) Shear
Answer: c
Clarification: Burning is NOT a method used for size reduction.
5. Statement 1: Grinding laws are based on the energy required for the creation of new surface area.
Statement 2: In general, all the laws are based on the principle that the energy required per unit area of the surface is directly proportional to the size of the particle.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: b
Clarification: Grinding laws are based on the energy required for the creation of new surface area. In general, all the laws are based on the principle that the energy required per unit area of the surface is directly proportional to the size of the particle.
6. Statement 1: A hammer mill uses an impact to break particles.
Statement 2: A chakki uses compression to break particles.
a) True, False
b) True, True
c) False, False
d) False, True
Answer: a
Clarification: A chakki uses attrition to break particles.
7. Kick’s law is an intermediate between rittinger’s law and bond’s law.
a) True
b) False
Answer: b
Clarification: Bond’s law is an intermediate between rittinger’s law and kick’s law.
8. A jaw crusher uses _____
a) Compression
b) Shear
c) Cutting
d) None of the mentioned
Answer: a
Clarification: A jaw crusher uses Compression.
9. A ball mill uses _____
a) Impact
b) Attrition
c) Impact & Attrition
d) None of the mentioned
Answer: c
Clarification: A ball mill uses both impacts when the solids fall from the top to the bottom and attrition when the particles rub against each other and reduce in size.
10. Which of the following uses attrition?
a) Ball mill
b) Plate mill
c) Roller mill
d) All of the mentioned
Answer: d
Clarification: All of the mentioned use attrition for size reduction.