Drying of Fruits and Vegetables
1. The efficiency of the dryer is in range of:
a. 85-90%
b. 95-100%
c. 90-95%
d. 65-75%
Ans. d
2. Fluidized bed dryer is used for drying:
a. Milk
b. Tea leaves
c. Fruit juices
d. Vegetables
Ans. b
3. In freeze drying the removal of moisture takes place due to:
a. Boiling
b. Condensation
c. Sublimation
d. Pressure reduction
Ans. 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
Ans. a
5. Constant rate of heating takes at:
a. 1000 degree C
b. 1200 degree C
c. 1150 degree C
d. All temperatures
Ans. d
6. EMC of a product changes with ………… of the environment:
a. Temperature
b. RH
c. Temperature and RH
d. Pressure
Ans. 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
Ans. b
Drying Food Preservation Examples
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%
Ans. b
9. Volatile compounds are retained in:
a. Spray dryer
b. Impringement dryer
c. Cabinet dryer
d. Rotary dryer
Ans. d
10. The safe moisture for storing the grains is:
a. 14%
b. 20%
c. 4%
d. 25%
Ans. a
11. In cabinet dryer the product attains…… temperature than the used air:
a. Higher
b. Same
c. Lower
d. 10 times higher
Ans. c
12. The average particle size in spray dryer is:
a. 10pm
b. 100pm
c. 0.01pm
d. 50pm
Ans. b
13. 20% M.C. (w.b.) is equal to ……… M.C. in dry basis:
a. 10%
b. 15%
c. 20%
d. 25%
Ans. 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
Ans. 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
Ans. c
16. Natural air-drying needs dehumidification if atmospheric humidity is:
a. Very less
b. Low
c. Intermediate
d. High
Ans. 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
Ans. a
Difference between Drying and Dehydration MCQs
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
Ans. 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
Ans. 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
Ans. c
21. The process of removal of moisture from moist ar known as …… process:
a. Humidification
b. Cooling
c. Dehumidification
d. Drying
Ans. 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%
Ans. 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
Ans. 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
Ans. 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
Ans. b
What is Dehydration of Food in What way is this technique useful
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
b. EMC
c. Water activity
d. Dry matter
Ans. 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
Ans. 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
Ans. 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
Ans. 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
Ans. 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
Ans. a
Methods of Dehydration of Fruits and Vegetables
33. Method of drying used for heat sensitive produce is:
a. Spray drying
b. Tray drying
c. Flow drying
d. Freeze drying
Ans. 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
Ans. 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
Ans. b
36. LSU drier is a type drier:
a. Continuous mixing
b. Non mixing
c. Thin layer
d. Deep bed
Ans. a
37. The optimum moisture content for paddy harvesting is …..%:
a. 20
b. 22
c. 24
d. 26
Ans. b
38. Parboiling of paddy is treatment:
a. Hydration
b. Dehydration
c. Thermal
d. Hydrothermal
Ans. d
39. Two fluid nozzle is used in a:
a. Spray drier
b. Drum drier
c. Fluidized bed drier
d. Freeze drier
Ans. 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
Ans. c
41. Sensible cooling of air….. RH of air:
a. Increases
b. Dereases
c. Does not change
d. Both a and b
Ans. a
Dehydration Methods of Food Preservation pdf
42. Holding a grain between two drying passes is termed as:
a. Stabilizing
b. Tempering
c. Cooling
d. Equalizing
Ans. b
43. Density of air at normal conditions is approximately ……. kg/m3:
a. 1.0
b. 1.2
c. 1.4
d. 1.6
Ans. b
44. Isobaric process are those in which…… is maintained constant:
a. Temperature
b. Volume
c. Pressure
d. Humidity
Ans. c
Sun (Solar) Drying of Fruits and Vegetables
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
Ans. c
46. When the temperature of air increases, the RH:
a. Increases linearly
b. Decreases
c. Does not change
d. Increases exponentially
Ans. b
47. In spray dryer, the pressure nozzle requires…… pressure:
a. 200kg/cm2
b. 25kg/cm2
c. 50kg/cm2
d. 75kg/cm2
Ans. a
48. In drying process the moisture removal takes place by:
a. Radiation
b. Conduction
c. Diffusion
d. Convection
Ans. 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
Ans. a
50. Mixing type columnar dryer is used for:
a. Liquid materials
b. Granular materials
c. Leafy materials
d. Powder materials
Ans. b
Drying and Dehydration Books