Category: Food Processing Unit Operations Objective Questions

250+ TOP MCQs on Heat Transfer Applications – Continuous Flow Heat Exchangers and Answers

Food Processing Unit Operations Interview Questions and Answers for freshers on “Heat Transfer Applications – Continuous Flow Heat Exchangers”.

1. What type of heat exchanger used in oil refineries?
a) Shell and tube Heat exchanger
b) Plate heat exchanger
c) Finned tube heat exchanger
d) Plate fin heat exchanger
Answer: a
Clarification: Shell and tube Heat exchanger is used in oil refineries and is appropriate for high pressure applications. The hydraulic fluids and the oils in the engines are cooled by using this exchanger. It comprises a number of tubes attached inside a cylindrical shell. The two fluids can transfer the heat where one fluid flows inside the tubes and other fluid flows over the tubes.

2. Air Cooled Heat Exchangers are used in ___________
a) oil refineries
b) vehicles
c) food industries
d) dairy industries
Answer: b
Clarification: Air Cooled Heat Exchangers are used in vehicles where stable cool water source is not available. Cool air is provided by air flow due to vehicle movement or by fans.

3. What are the examples of indirect heat exchangers?
a) Shell and tube Heat exchanger, Plate heat exchangers
b) Steam injectors, plate heat exchangers
c) Cooling towers, Plate heat exchangers
d) Steam injectors, cooling towers
Answer: a
Clarification: Indirect heat exchanger, the two fluids can transfer the heat where one fluid flows inside the tubes and other fluid flows over the tubes. Shell and tube Heat exchanger, Plate heat exchangers are the examples of indirect heat exchangers. Steam injectors, cooling towers are the examples of direct heat exchangers.

4. What are the examples of direct heat exchangers?
a) Shell and tube Heat exchanger, Plate heat exchangers
b) Steam injectors, plate heat exchangers
c) Cooling towers, Plate heat exchangers
d) Steam injectors, cooling towers
Answer: d
Clarification: In direct heat exchangers, there is a direct contact between the two immiscible fluids for transferring the heat. Cooling towers, jet condensers, steam injectors are the examples of direct heat exchangers.

5. What type of heat exchanger is used in cryogenic applications?
a) Shell and tube Heat exchanger
b) Plate heat exchanger
c) Finned tube heat exchanger
d) Plate fin heat exchanger
Answer: d
Clarification: Plate fin heat exchangeris used in cryogenic applications. They use corrugated fins which are separated by flat plates. These are used in gas-to-gas applications at where it has low pressures and temperatures not above 800°C.

6. Which of the following statements about Printed circuit heat exchanger are correct?
Statement 1: Printed circuit heat exchanger is an example for direct heat exchanger.
Statement 2: It has high heat transfer surface area per unit volume of the exchanger.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: c
Clarification: Printed circuit heat exchanger is an example for indirect heat exchanger. It can be used as alternatives to shell and tube heat exchanger. It has high heat transfer surface area per unit volume of the exchanger. It also reduces the energy requirement. But it is expensive than shell and tube units and the fluid needs to be extremely clean or else blockages can occur due to the fine channels. Therefore the fluids are filtered before the feeding into inlet pipe.

7. _____________ consists of a single tube mounted inside another tube.
a) Shell and tube Heat exchanger
b) Plate heat exchanger
c) Double tube heat exchanger
d) Plate fin heat exchanger
Answer: c
Clarification: Double pipe heat exchanger contains of two concentric pipes of different diameters. One pipe is for cold fluid and the other one is for hot fluid.The fluid can flowin co-current direction or counter current direction.

8. _________ is used as rear header in a U-Tube heat exchanger.
a) M type
b) A type
c) U type
d) D type
Answer: a
Clarification: M typeis used as rear header in a U-Tube heat exchanger. The U-tubes permit unlimited thermal extension, the bundles of the tubes can be removed to clean. But internal cleaning of the tubes are difficult due to the small diameter, therefore the fluids are filtered before entering into the feed pipe.

9. __________is used for horizontal thermosyphon reboilers.
a) G type
b) A type
c) C type
d) Y type
Answer: a
Clarification: G typefront header is used for horizontal thermosyphon reboilers. A-Type front header is used for easy cleaning or repair of the tubes without having to disturb the pipe work. C type header is for high pressure applications. Y-Type header used as a front or rear header and is used when the exchanger is in pipe line.

10. __________ uses an intermediate fluid or solid store to hold heat.
a) Shell and tube Heat exchanger
b) Plate heat exchanger
c) Double tube heat exchanger
d) Adiabatic wheel heat exchanger
Answer: d
Clarification: Adiabatic wheel heat exchangercontains a wheel and uses an intermediate fluid to hold heatand then the heat is transferred to the other side of the heat exchanger. It is used in transfer of heat between gases efficiently which is not easily possible in other heat exchanger.

250+ TOP MCQs on Mechanical Separation – Centrifugation Equipment and Answers

Food Processing Unit Operations Multiple Choice Questions on “Mechanical Separation – Centrifugation Equipment”.

1. What is maximum speed of low speed centrifuge?
a) 1000-2000rpm
b) 3000-4000rpm
c) 4000-5000rpm
d) 5000-6000rpm
Answer: c
Clarification: Most laboratories have a low-speed centrifuge used for routine sedimentation of heavy particles and the low-speed centrifuge has a maximum speed of 4000-5000rpm.

2. Which of the following used for sedimentation of red blood cells?
a) Low speed centrifuge
b) High speed centrifuge
c) Ultra centrifuge
d) Vacuum centrifuge
Answer: a
Clarification: Low speed centrifuge is used for sedimentation of red blood cells until the particles are tightly packed into a pellet and supernatant is separated by decantation.

3. What is maximum speed of high speed centrifuge?
a) 10000-20000rpm
b) 15000-20000rpm
c) 30000-50000rpm
d) 50000-60000rpm
Answer: b
Clarification: High-speed centrifuges are used in biochemical applications. The high-speed centrifuge has a maximum speed of 15,000 – 20,000 RPM.

4. What are factors that affect high-speed centrifuges?
a) Speed and temperature
b) Pressure and temperature
c) Concentration and speed
d) Pressure and speed
Answer: a
Clarification: High-speed centrifuges are used in biochemical applications, the factors that affect are higher speeds and temperature control of the rotor chamber.

5. Which of the following statements about ultracentrifugeare correct?
Statement 1: Ultracentrifuge has a maximum speed of 85,000 RPM.
Statement 2: It is used for both preparative work and analytical work.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: c
Clarification: Ultracentrifuge has a maximum speed of 65,000 RPM. Intense heat is generated due to high speed thus the spinning chambers must be refrigerated and kept at a high vacuum. It is used for both preparative work and analytical work.

6. Identify the type of centrifuge equipment.

a) Horizontal bowl scroll discharge
b) Longitudinal bowl scroll discharge
c) Vertical bowl scroll discharge
d) Latitude bowl scroll discharge
Answer: a
Clarification: In horizontal bowl scroll discharge, centrifugal forces cause immediate sedimentation of the solids on the wall of bowl. The conveyor rotates in the same direction as the bowl, but at different speed, thus moving the solids near the conical end of the bowl.

7. Which industry uses centrifuge test?
a) Sugar industry
b) Oil industry
c) Bakery industry
d) Salt industry
Answer: b
Clarification: Oil industries uses centrifuge test. A Centrifuge test is a fully programmable process which allows automatic configuration of specified oil test parameters.

8. What is the other name for screen centrifuge?
a) Low speed centrifuge
b) High speed centrifuge
c) Ultra centrifuge
d) Conveyor discharge centrifuge
Answer: d
Clarification: Screen centrifuge is also known as worm screen or conveyor discharge centrifuge. It is widely used for the separation of crystalline, granular or fibrous materials from a solid-liquid mixture.

9. Which centrifuge used for separating caffeine?
a) Low speed centrifuge
b) Peeler centrifuge
c) Ultra centrifuge
d) Conveyor discharge centrifuge
Answer: b
Clarification: Peeler centrifuge is used for separating caffeine. The peeler centrifuge has rotating filtration basket connected in at axis. The principle of centrifugal force is to separate solids from liquids by density difference.

10. What is the fixed angle of rotors in centrifuge?
a) 10° and 20°
b) 14° and 40°
c) 20° and 40°
d) 34° and 48°
Answer: b
Clarification: In fixed angles, the tubes are fixed at angle between 14° and 40° to the vertical. Under the influence of centrifugation particles move radially outward and have short distance to travel before colliding withthe outer wall of the centrifuge tube.

250+ TOP MCQs on Distillation Basics and Answers

Food Processing Unit Operations Multiple Choice Questions on “Distillation Basics”.

1. What are the two processes in distillation?
a) Distilling and freezing
b) Distilling and condensation reflux
c) Freezing and condensation reflux
d) Only condensation reflux
Answer: b
Clarification: Distillation is the process where it consists of two processes of distilling and condensation reflux. It is usually carried out in distillation column, the gas-liquid two-phase flow through the countercurrent contact.

2. What are the basic methods of distillation?
a) Fractional distillation and simple distillation
b) Fractional distillation, destructive distillation and simple distillation
c) Steam distillation, simple distillation and gas distillation
d) Steam distillation and destructive distillation
Answer: b
Clarification: Simple distillation, fractional distillation where different volatile fractions are collected as during the process and destructive distillation where a material is heated so that it decomposes into compounds for collection.

3. Who discovered distillation?
a) Jabir ibn Hayyan
b) Guldberg and Waage
c) Charles Chamberland
d) Clarence Birdseye
Answer: a
Clarification: Jabir ibn Hayyan discovered distillation. Guldberg and Waage recognized that chemical equilibrium. Clarence Birdseye developed freezing process. Charles Chamberland developed steam pressure sterilizer.

4. What apparatus is used in distillation?
a) Distillation flask, condenser, collection vessel
b) Distillation flask, condenser
c) Condenser, collection vessel
d) Distillation flask, column
Answer: a
Clarification: Distillation apparatus consists of three units, they are distillation flask which is used for heating the mixture and volatizing the components. Next is condenser for cooling the vapors back to liquid state and lastly collection vessel for collecting the end product.

5. Where is double distillation method used?
a) To prepare distilled water for laboratory purposes
b) To produce distilled water for commercial purposes
c) To produce wine for commercial purposes
d) To produce coffee for commercial purposes
Answer: a
Clarification: Double distillation consists of flak with heating elements. It is used for carrying out the reactions under stirred conditions besides furnishing for reflux distillation. It is used to prepare distilled water for laboratory research.

6. What is the distillate in distillation?
a) Vapor collected from the mixture
b) Liquid present in the distillation column
c) Vapor introduced during distillation process
d) Liquid introduced during distillation process
Answer: a
Clarification: A distillate in the distillation process is defined as the vapor in a distillation column that is collected and condensed into a liquid and collected in the collecting flask.

7. Why is steel wool used in fractional distillation?
a) Increases the surface area
b) Improves the separation between the liquids
c) Increases the surface area and improves the separation between the liquids
d) Increases the surface area and the quality of the distillate
Answer: c
Clarification: Fractionating column is filled with a packing material like glass, steel wool and plastic beads. It increases the surface area and improves the separation between the liquids being distilled.

8. Does vacuum distillation higher boiling point?
a) True
b) False
Answer: b
Clarification: The vacuum distillation happens at a considerable reduced pressure, therefore reduces the boiling point of a substance.

9. Which of the following is produced by triple distillation method?
a) Coffee
b) Beer
c) Whisky
d) Wine
Answer: c
Clarification: Triple distillation is defined as the process where smooth whiskies are manufactured. Through refining the spirit over three distillations, it concentrates a particular fraction of flavorful compounds and aromatic substance that results in a very smoother taste.

10. Why porcelain pieces are used in distillation?
a) To have uniform boiling
b) To hasten the process
c) To add weight for the substance
d) To absorb excess heat from the flask
Answer: a
Clarification: The porcelain pieces or the glass beads are put in the distillation flask in the beginning to have uniform boiling throughout the solution and avoid bumping of the solution due to uneven heating.

250+ TOP MCQs on Drying Equipments and Answers

Food Processing Unit Operations Multiple Choice Questions on “Drying Equipments”.

1. Which of the following dryer is used for pureed raw ingredients that are dried at relatively low temperatures over rotating?
a) Fluidized bed dryer
b) Drum dryer
c) Cabinet tray dryer
d) Pneumatic dryer
Answer: b
Clarification: In the drum dryer, the pureed raw ingredients are dried at low temperatures over rotating. The additional advantage of this drier is that product is milled to produce powder or flakes form.

2. Which of the following dryer is used to produce powder from the solution?
a) Spray dryer
b) Cabinet tray dryer
c) Pneumatic dryer
d) Fluidized bed dryer
Answer: a
Clarification: Spray dyer is used to produce powder from the solution. It dries the solution stream and separates the solute and evaporates the solvent and forms vapor. The solid particles are collected in a cyclone or drum.

3. Who invented spray dryer?
a) Samuel Percy
b) Fritz Winkler
c) John A
d) Jacques-Arsened’Arsonva
Answer: a
Clarification: Samuel Percy invented spray dryer. Fritz Winkler invented fluidized bed dryer. John A invented drum dryer. Jacques-Arsened’Arsonva invented freeze dryer.

4. What is the alternative name for batch-in-bin dryer?
a) Flat bed dryer
b) Cabinet tray dryer
c) Pneumatic dryer
d) Fluidized bed dryer
Answer: a
Clarification: Batch-in-bin dryer is also known as flat bed dyer. Its capacity is of 1-3 tons per day with 6-12 hours of drying times. The batch-in-bin dryer is easy to construct and is inexpensive and simple to operate and require unskilled labor.

5. What is full form of LSU dryer?
a) Louisiana State University dryer
b) Low simple universal dryer
c) Low and slow unit dryer
d) Level steady unit dryer
Answer: a
Clarification: In Louisiana State University dryer, the drying section contains vertical compartment across which rows of air channels are fitted. Alternate rows are closedwhere the moving stream of grain from the top descends thus providing considerable mixing.

6. Which of the following statements about LSU dryer are correct?
Statement 1: LSU dryer is mainly used to dry the grains.
Statement 2: LSU is a continuous flow mixing type of dryer.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: LSU is a continuous flow mixing type of dryer. LSU dryer is mainly used to dry the grains. It is popular in India and USA. The capital investment is high. The recommended air flow rate is 60-70m3/ min/ ton.

7. What does Fritz Winkler invented?
a) Fluidized bed dryer
b) Drum dryer
c) Spray dryer
d) Freeze dryer
Answer: a
Clarification:Samuel Percy invented spray dryer. Fritz Winkler invented fluidized bed dryer. John A invented drum dryer. Jacques-Arsened’Arsonva invented freeze dryer.

8. Which dryer is used to dry the material almost instantaneously in a turbulent stream of hot air?
a) Fluidized bed dryer
b) Drum dryer
c) Cabinet tray dryer
d) Pneumatic dryer
Answer: d
Clarification: In pneumatic dryer, the material is dried almost instantaneously in a turbulent stream of hot air. This can also acts as conveyor system. It is applicable to powdered, granular, and flaky materials.

9. Which of the following dryer is the convectional drying equipment with enclosed insulated chambers?
a) Fluidized bed dryer
b) Drum dryer
c) Cabinet tray dryer
d) Pneumatic dryer
Answer: c
Clarification: Cabinet tray dryer is conventional drying equipment with enclosed insulated chambers. The trays are placed on top of each other in a trolley. The mode of heat transfer is forced convention.

10. What type of dryer is used for the drying of substances which are hygroscopic?
a) Fluidized bed dryer
b) Drum dryer
c) Cabinet tray dryer
d) Vacuum dryer
Answer: d
Clarification: Vacuum Tray dryer is the most commonly used batch dryer. Vacuum Tray Dryer is used for drying of hygroscopic substances and heat sensitive materials, which are dried to very low residual moisture content level.

250+ TOP MCQs on Heat Radiation and Answers

Food Processing Unit Operations Multiple Choice Questions on “Heat Radiation”.

1. Which is the fastest mode of heat transfer?
a) Conduction
b) Convection
c) Radiation
d) Both conduction and convection
Answer: c
Clarification: The fastest mode of heat transfer is radiation as it travels at the speed of light. Conduction is the slowest mode of heat transfer because it takes place from particle to particle.

2. Which law governs the thermal radiation?
a) Fourier’s law
b) Pascal law
c) Newton law
d) Stefan-Boltzmann Law
Answer: d
Clarification: Stefan-Boltzmann Lawgoverns the thermal radiation. It statesthat the total radiant heat power emitted from a surface is proportional to the fourth power of its absolute temperature.

3. Are these statements about the thermal radiation true?
Statement 1: It follows Stefan-Boltzmann Law.
Statement 2: It also depends on Wien’s Displacement Law.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: Thermal radiation follows Planks law and also Wien’s Displacement Law. Stefan-Boltzmann Law states that the total radiant heat power emitted from a surface is proportional to the fourth power of its absolute temperature.Wien’s Displacement Law states that a hotter object will emit radiation with a shorter wavelength.

4. The emissivity of radiation is between__________
a) 0 and 1
b) 0 and 10
c) 0 and 15
d) 0 and 11
Answer: a
Clarification: The emissivity of radiation is between0 and 1. It can be defined as the ratio of the thermal radiation from the surface to the radiation from an ideal black surface at a constant temperature. This is derived under Stefan–Boltzmann law.

5. In thermal radiation, thermal energy is converted to ___________________
a) kinetic energy
b) potential energy
c) electromagnetic energy
d) thermal energy
Answer: c
Clarification: In thermal radiation, thermal energy is converted to electromagnetic energy. This is achieved by the thermal motion of the particles in the substance. All the substance with a temperature greater than absolute zero emits the thermal radiation. The motion of the particle results in acceleration of charge and dipole oscillation which produces electromagnetic energy.

6. What is the wavelength of thermal radiation?
a) 0.1 μm to 1000 μm.
b) 1 μm to 100 μm.
c) 0.01 μm to 100 μm.
d) 0.1 μm to 100 μm.
Answer: d
Clarification: The thermal radiation is the electromagnetic radiation emitted from all the substance that is at non-zero temperature in the wavelength ranging from 0.1 μm to 100 μm. This includes part of ultraviolet rays, all of the visible and infrared rays.

7. Can a good insulator prevent radiation?
a) True
b) False
Answer: a
Clarification: Hot objects radiate infra-red electromagnetic waves, so therefore insulation against heat transfer by radiation is done by using reflective materials. The thermos bottle has a shiny material along with a lining to prevent heat conduction. This shiny material reflects heat from the radiation from inside as well as outside the bottle.

8. What are factors of thermal radiation?
a) Time
b) Temperature
c) Volume
d) Pressure
Answer: b
Clarification: Temperature plays an important factor in thermal radiation. The heat capacity is defined as the ratio of amount of heat energy supplied and change in temperature. According to Stefan-Boltzmann Law, the total radiant heat power emitted from a surface is proportional to the fourth power of its absolute temperature.

9. According to ___________, the wavelength of the emitted radiation is inversely proportional to its frequency.
a) Fourier’s law
b) Pascal law
c) Newton law
d) Plank’s law
Answer: d
Clarification: According to Plank’s law, the wavelength of the emitted radiation is inversely proportional to its frequency. It is defined as the spectral density of the electromagnetic energy emitted by a black body in thermal equilibrium at a given temperature normally when the net flow of energy and matter is zero between the body and its environment.

10. ____________ gives the relationship between wavelength and temperature.
a) Fourier’s law
b) Wein’s law
c) Newton law
d) Plank’s law
Answer: b
Clarification: Wein’s law gives the relationship between wavelength and temperature. Wien’s displacement law is defined as the spectral radiance of black body radiation per unit wavelength. The maximum wavelength can be calculated by dividing Wien’s displacement constant with Temperature.

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250+ TOP MCQs on Process Engineering Applications – Meat Industry and Answers

Food Processing Unit Operations Multiple Choice Questions on “Process Engineering Applications – Meat Industry”.

1. What is meat emulsion?
a) Finely chopped meat mixture
b) Emulsifiers added to meat
c) By product of meat industry
d) Stabilizers added to meat
Answer: a
Clarification: A finely chopped meat mixture is usually called as meat emulsion. It consists of solid fat particles dispersed in a mixture of water and many fibrous particles, including connective tissue and muscle fibers.

2. Why is tumbling of meat recommended?
a) Avoid foaming
b) Increases efficiency
c) Increase efficacy
d) Decreases power consumption
Answer: a
Clarification: Tumblers are containers in the form of a cylinder rotating around the axis. Tumbling under vacuum is recommended to avoid foaming and to improve color stability.

3. What is the temperature of pasteurization for meat?
a) 73°C
b) 89°C
c) 63°C
d) 65°C
Answer: a
Clarification: Pasteurization is normally defined as a method of preserving food by heating it to temperatures under 100°C. It destroys the microbes and temperature of pasteurization for meat is 73°C.

4. Which of the following statements about heat treatment of meat products are correct?
Statement 1: To increase the shelf life of the product.
Statement 2: To obtain desirable organoleptic characteristics.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: During meat processing, meat products are subject to specific heat treatment. This is done to increase shelf-life by reduction of micro-organisms, obtain desirable organoleptic characteristics, to preserve nutritive value and improve digestibility of the product.

5. What is evisceration?
a) Removing internal body parts of bird
b) Removing feathers
c) Cleaning the skin of bird
d) Preservation technique of bird
Answer: a
Clarification: Evisceration is defined as removal of the internal organs of birds. After evisceration, the birds are placed in chiller baths of water and anti-microbial agents are added to reduce pathogen loading.

6. What is giblet harvester?
a) Removes the viscera from the body cavity
b) Separates the heart, liver, and gizzard from the rest of the viscera
c) Trim and clean gizzards
d) Cut the neck of the bird
Answer: b
Clarification: The liver, gizzard, and heart are separated by giblet harvester from the rest of the intestines by a saw. Then these organs are conveyed to a wash table where a prime cleaning is done.

7. What is arranger in meat processing?
a) Removes the viscera from the body cavity
b) Separates the heart, liver, and gizzard from the rest of the viscera
c) Trim and clean gizzards
d) Cut the neck of the bird
Answer: a
Clarification: Arranger removes the intestines from the body cavity and are arranged them for inspection. The initial removal is often skilled by the automatic vent opening mechanism. The arranger is also called as presenter.

8. What is the gizzard table operator in meat processing?
a) Removes the viscera from the body cavity
b) Separates the heart, liver, and gizzard from the rest of the viscera
c) Trim and clean gizzards
d) Cut the neck of the bird
Answer: c
Clarification: The gizzard table operators manually trim and clean the gizzards. They are then placed in an automatic splitting machine where they are opened up and washed in the gizzard peeler station.

9. Which of the following statements about stunning in meat processing are correct?
Statement 1: It reduces animal’s mobility.
Statement 2: Percussive stunning produces immediate unconsciousness through brain trauma.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: Stunning is the method of rendering animals unconscious or immobile, immediately prior to slaughtering. With percussive stunning, a device hits the animal on the head and produces immediate unconsciousness through brain trauma.

10. What gas is used for gas stunning in meat processing?
a) Argon
b) Helium
c) Carbon dioxide
d) Ammonia
Answer: a
Clarification: Gas stunning is the process where the animals are exposed to a mixture of breathing gases such as nitrogen and argon which produces unconsciousness and death through hypoxia. This process is not instantaneous.