300+ Drying & Dehydration of Food Materials MCQs & Answers

Drying & Dehydration of Food Materials | Drying of Fruits and Vegetables Multiple Choice Questions

1. The efficiency of the dryer is in range of:

A. 85-90%

B. 95-100%

C. 90-95%

D. 65-75%

Answer: D

2. Fluidized bed dryer is used for drying:

A. Milk

B. Tea leaves

C. Fruit juices

D. Vegetables

Answer: B

3. In freeze drying the removal of moisture takes place due to:

A. Boiling

B. Condensation

C. Sublimation

D. Pressure reduction

Answer: C

4. If the addition of heat does not change temperature it is known as:

A. Latent heat

B. Sensible heat

C. Super heat

D. Saturated heat

Answer: A

5. Constant rate of heating takes at:

A. 1000 degree C

B. 1200 degree C

C. 1150 degree C

D. All temperatures

Answer: D

6. EMC of a product changes with ………… of the environment:

A. Temperature


C. Temperature and RH

D. Pressure

Answer: B

7. The vapour pressure of the moisture in the materials due to addition of heat:

A. Decreases

B. Increases

C. Decreases initially and increases

D. Does not change

Answer: B

8. If the moisture content on dry basis is 25%, then what would be moisture content on wet basis?

A. 18%

B. 20%

C. 22%

D. 25%

Answer: B

9. Volatile compounds are retained in:

A. Spray dryer

B. Impringement dryer

C. Cabinet dryer

D. Rotary dryer

Answer: D

10. The safe moisture for storing the grains is:

A. 14%

B. 20%

C. 4%

D. 25%

Answer: A

Drying & Dehydration of Food Materials MCQs

11. In cabinet dryer the product attains…… temperature than the used air:

A. Higher

B. Same

C. Lower

D. 10 times higher

Answer: C

12. The average particle size in spray dryer is:

A. 10pm

B. 100pm

C. 0.01pm

D. 50pm

Answer: B

13. 20% M.C. (w.b.) is equal to ……… M.C. in dry basis:

A. 10%

B. 15%

C. 20%

D. 25%

Answer: D

14. The recommended temperature of drying of grains for seed purpose is about:

A. 40 degree C

B. 50 degree C

C. 60 degree C

D. 70 degree C

Answer: A

15. 100kg of grain is dried from 18% (w.b) to 13% (w.b). The amount of water removed is:

A. 4.8 kg

B. 5 kg

C. 5.7kg

D. 6.2kg

Answer: C

16. Natural air-drying needs dehumidification if atmospheric humidity is:

A. Very less

B. Low

C. Intermediate

D. High

Answer: D

17. In drying, end of constant rate period and start of falling rate period is known as:

A. Critical moisture content

B. Equilibrium moisture content

C. Constant drying rate period

D. Falling rate period

Answer: A

18. Dryers utilizing high gas temperatures of 500 degree C or more, but for short exposure of time are called as:

A. Fluidized bed dryers

B. Flash dryers

C. Turbol dryers

D. Drum dryers

Answer: B

19. The water activity of the surface of a food product at the end of constant drying rate:

A. Remains constant at 1

B. Drops below 1

C. Equals to zero

D. Drops below 2

Answer: B

20. In single effect evaporator the economy is:

A. Equal to 1

B. More than 1

C. Less than 1

D. More than 10

Answer: C

21. The process of removal of moisture from moist ar known as …… process:

A. Humidification

B. Cooling

C. Dehumidification

D. Drying

Answer: C

22. When dry bulb and wet bulb temperature are same the RH of air will be:

A. 0%

B. 50%

C. 100%

D. 70%

Answer: C

23. Thermal radiation emitted by a body is proportional to of its absolute temperature:

A. Fourth power

B. Square

C. Square root

D. Cube root

Answer: A

24. The heat which causes increase or decrease in the temperature of a body without changing its state is known as:

A. Latent heat

B. Specific heat

C. Sensible heat

D. Total heat

Answer: C

25. A property used to measure the gravity of energy or irreversibility of the process is called as:

A. Enthalpy

B. Entrop

C. Diffusivity

D. Conductivity

Answer: B

26. The universal moisture meter measures ………. of the grain at given comparison:

A. Electrical conductivity

B. Electrical resistance

C. Diffusivity

D. Thermal conductivity

Ans, b

27. BET equation is used for measuring the…….. of food:

A. Moisture humidity


C. Water activity

D. Dry matter

Answer: C

28. The ratio of kg of water vapour and kg of dry air is:

A. Relative humidity

B. Percentage humidity

C. Absolute humidity

D. Humid volume

Answer: C

29. In the process where there is change from one condition to other condition without transfer of heat between system and atmosphere or surrounding during the entire process is known as:

A. Isothermal

B. Isoentropic

C. Adiabatic

D. Isobaric

Answer: C

30. During sensible heating or cooling there is no change in the values of:

A. Relative humidity

B. Humidity ratio

C. Specific humidity

D. Absolute humidity

Answer: B

31. The vapour pressure of the water in grain lower than the vapour pressure of free water surface is known as:

A. Bound water

B. Unbound water

C. Free water

D. Surface water

Answer: A

32. In thin layer drying, the thickness of grain is normally up to:

A. 15-20 cm

B. 20-25cm

C. 25-30cm

D. 30-35cm

Answer: A

33. Method of drying used for heat sensitive produce is:

A. Spray drying

B. Tray drying

C. Flow drying

D. Freeze drying

Answer: D

34. Due to moisture migration the spot of moisture accumulation takes place at….. of storage structure during winter:

A. Top

B. Bottom

C. Centre

D. Side

Answer: A

35. The factors influencing the diameter of drying chamber in the spray dryer design are:

A. Velocity of drying air

B. Atomizer speed

C. Density of air

D. Temperature of inlet air

Answer: B

36. LSU drier is a type drier:

A. Continuous mixing

B. Non mixing

C. Thin layer

D. Deep bed

Answer: A

37. The optimum moisture content for paddy harvesting is …..%:

A. 20

B. 22

C. 24

D. 26

Answer: B

38. Parboiling of paddy is treatment:

A. Hydration

B. Dehydration

C. Thermal

D. Hydrothermal

Answer: D

39. Two fluid nozzle is used in a:

A. Spray drier

B. Drum drier

C. Fluidized bed drier

D. Freeze drier

Answer: A

40. At 100% RH, wet bulb temperature is…. dew point temperature:

A. More than

B. Less than

C. Same as

D. Less or more

Answer: C

41. Sensible cooling of air….. RH of air:

A. Increases

B. Dereases

C. Does not change

D. Both a and b

Answer: A

42. Holding a grain between two drying passes is termed as:

A. Stabilizing

B. Tempering

C. Cooling

D. Equalizing

Answer: B

43. Density of air at normal conditions is approximately ……. kg/m3:

A. 1.0

B. 1.2

C. 1.4

D. 1.6

Answer: B

44. Isobaric process are those in which…… is maintained constant:

A. Temperature

B. Volume

C. Pressure

D. Humidity

Answer: C

45. The RH will be reduced to half of its original value if the temperature of air is increased by:

A. 21 degree C

B. 15 degree C

C. 11 degree C

D. 8 deggree C

Answer: C

46. When the temperature of air increases, the RH:

A. Increases linearly

B. Decreases

C. Does not change

D. Increases exponentially

Answer: B

47. In spray dryer, the pressure nozzle requires…… pressure:

A. 200kg/cm2

B. 25kg/cm2

C. 50kg/cm2

D. 75kg/cm2

Answer: A

48. In drying process the moisture removal takes place by:

A. Radiation

B. Conduction

C. Diffusion

D. Convection

Answer: C

49. Energy required for removal of bound moisture from the materials is….. free moisture:

A. More than

B. Half of the

C. Equal to

D. 10 times higher than the

Answer: A

50. Mixing type columnar dryer is used for:

A. Liquid materials

B. Granular materials

C. Leafy materials

D. Powder materials

Answer: B

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