Engineering Questions with Answers - Multiple Choice Questions
Food Engineering MCQ’s – Unit Operations – Dehydration-2
1 - Question
Statement 1: Cabinet tray dyers can be used for heat sensitive materials.
Statement 2: Bin dryer is used for materials which follow the falling rate drying curve.
a) True, False
b) True, True
c) False, False
d) False, True
View Answer
Explanation: Cabinet tray dyers cannot be used for heat sensitive materials as materials are exposed to the drying medium for several hours. Bin dryer is used for materials which follow the falling rate drying curve as the materials in the bin follow a gradient of moisture content from bottom to top of the bin.
2 - Question
Advantage of turbo dryer over cabinet tray dryer is _____
a) It is more effective
b) The feed is uniformly heated at the edges
c) None of the mentioned
d) It is more effective & the feed is uniformly heated at the edges
View Answer
Explanation: Advantage of turbo dryer over cabinet tray dryer is that the feed is uniformly heated at the edges.
3 - Question
Hannah ordered one ton of mushrooms. But, the entire lot was brown. Which dryer could it possibly have been?
a) Bin dryer
b) Tray dryer
c) Tower Dryer
d) Vacuum dryer
View Answer
Explanation: Browning of heat sensitive food items may take place due excess exposure to hot air. Tray dryer has a high residence time. Hence, it is the most possible guess out of the four.
4 - Question
Statement 1: Which tray dryer has indirect heating?
Statement 2: Which tray dryer is good for making powders?
a) Bin dryer, vacuum dryer
b) Tray dryer, vacuum dryer
c) Tower Dryer, vacuum dryer
d) Vacuum dryer, vacuum dryer
View Answer
Explanation: Vacuum dryer has indirect heating as hot air is generally not blown through it. Vacuum dryer is good for making powders.
5 - Question
Which of the following dryers requires non-sticky granular feed?
a) Rotary dryer
b) Fluidized bed dryer
c) Rotary & Fluidized bed dryer
d) None of the mentioned
View Answer
Explanation: Both rotary dryer and fluidized bed dryer require non-sticky granular feed.
6 - Question
After incipient fluidization, the pressure briefly _____
a) Increases
b) Decreases
c) Stays constant
d) Varies exponentially
View Answer
Explanation: After incipient fluidization, the pressure briefly decreases. This is because at incipient fluidization, the particles only become loose. They aren’t in contact with each other. They don’t start rising up. Hence, the pressure briefly decreases. Once they start moving up, the pressure increases.
7 - Question
Statement 1: Vibro-fluidized bed dryer can reduce the air flow rate consumptions as air is only used for drying and not for fluidizing.
Statement 2: _____ are often called desolventizers.
a) True, screw conveyor
b) True, pneumatic conveyor
c) False, screw conveyor
d) False, pneumatic conveyor
View Answer
Explanation: Vibro-fluidized bed dryer can reduce the air flow rate consumptions as air is only used for drying and not for fluidizing. Mechanical vibratory motion is used for fluidization. Screw conveyors are often called desolventizers because the main purpose is to remove the solvent from the pastes and not to recover it.
8 - Question
Which of the following dryers cannot take a feed in the form of pastes/slurries/sticky items?
a) Drum dryer
b) Screw conveyor dryer
c) Pneumatic dryer
d) Spray dryer
View Answer
Explanation: In a pneumatic dryer, feed in the form of pastes/slurries/sticky items cannot be taken.
9 - Question
Which of the following is also called a ring dryer?
a) Pneumatic conveyor dryer
b) Drum dryer
c) Freeze dryer
d) Spray dryer
View Answer
Explanation: Pneumatic conveyor dryer is also called a ring dryer because the feed is made to pass through a loop at one point and comes back there. (Not always-depends on drying)
10 - Question
Which of the following dryers is used for making baby food?
a) Pneumatic conveyor dryer
b) Drum dryer
c) Freeze dryer
d) Spray dryer
View Answer
Explanation: Drum dryers are used for making baby food mostly because they take feed in the form of slurries.
11 - Question
Coffee powders can be made from which of the following dryers?
a) Pneumatic conveyor dryer
b) Drum dryer
c) Freeze dryer
d) Spray dryer
View Answer
Explanation: Coffee powder is porous, hygroscopic and low in density. These are the desired properties for a spray dryer.
12 - Question
X-axis is temperature and Y-axis is pressure.
Which of the following curves is followed for freeze drying of prawns?a) AA’
b) BB’
c) ABO
d) A’OB’
View Answer
Explanation: BB’ shows the conversion of the feed directly from a solid (ice) phase to vapour phase. The pressure is kept constant and the temperature is increased.