Category: Food Processing Unit Operations Objective Questions

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.

250+ TOP MCQs on Mechanical Separation – Centrifugation and Answers

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

1. What is the principle of centrifugation?
a) Sedimentation principle
b) Filtration principle
c) Evaporation principle
d) Size reduction principle

Answer: a
Clarification: Centrifuge works using the sedimentation principle, due to centrifugal acceleration denser substances move outward in the radial direction and that are less dense are displaced and move to the center.

2. What is called centrifugation?
a) Separated through spinning
b) Separate components at higher temperature
c) Separate components at lower temperature
d) Separated through evaporation

Answer: a
Clarification: Centrifugation is the process where a mixture is separated through spinning. It is used to separate skim milk from whole milk, washing machine and blood cells from your blood plasma.

3. Who invented centrifugation?
a) Newton
b) G.G. Stokes
c) Antonin Prandtl
d) Al-Kindi

Answer: b
Clarification: G.G. Stokes invented sedimentation. Newton discovered gravity. Antonin Prandtl invented centrifugation. Al-Kindi invented distillation.

4. What is use of density gradient centrifugation?
a) To purify viruses, ribosomes, membranes
b) Toremovedirt
c) To remove fine particles
d) To remove large particles

Answer: a
Clarification: Density gradient centrifugation is used to purify viruses, ribosomes, membranes. A sucrose density gradient is created by gently overlaying lower concentrations of sucrose on higher concentrations in centrifuge tubes where particles of interest are placed on top in ultracentrifuges. The particles move through the gradient until they reach the same sucrose density and fraction is removed and analyzed.

5. Which of the following statements about differential pelleting centrifugation are correct?
Statement 1: Tissue such as the liver is homogenized by this method.
Statement 2: The overlying solution is placed in another centrifuge tube for progressing steps.
a) True, False
b) True, True
c) False, True
d) False, False

Answer: b
Clarification: Differential pelleting centrifugation is the most common type of centrifugation used. Tissue like liver is homogenized.After sedimentation, the bottom is called pellet and an overlying solution called supernatant. The overlying solution is then placed in another centrifuge tube for progressing steps.

6. What is other name for zonal centrifugation?
a) Isopyniccentrifugation
b) Gradient centrifugation
c) Density gradient centrifugation
d) Differential centrifugation

Answer: b
Clarification: Zonal centrifugation is also known as band or gradient centrifugation and relies on the concept of sedimentation coefficient. In this process, a density gradient is created in a test tube with sucrose and high density at the bottom.

7. Which centrifugation depends on buoyant densities?
a) Isopynic centrifugation
b) Gradient centrifugation
c) Density gradient centrifugation
d) Differential centrifugation

Answer: a
Clarification: Isopynic centrifugation depends on buoyant densities, not on the velocities. CsCl, NaI gradients are the self-forming gradients for macromolecules and nucleotides under centrifugal force.

8. What are applications of centrifugation?
a) To separate two miscible substances and analyze the hydrodynamic properties of macromolecules
b) To separate two miscible substances and water treatment
c) Purification of mammalian cells and water treatment
d) Analyze the hydrodynamic properties of macromolecules and water treatment

Answer: a
Clarification: Applications of centrifugation are separation of two miscible substances, to analyze the hydrodynamic properties of macromolecules, purification of mammalian cells, separating chalk powder from water and removing fat from milk to produce skimmed milk.

9. Is centrifugation used in wine processing?
a) True
b) False

Answer: a
Clarification: Centrifugation is used in wine processing where the wine is clarified and stabilized by using centrifugation process.It is similar to sedimentation principle, where the centrifugal accelerates the denser substances to move outward in the radial direction and that are less dense are displaced and move to the center.

10. Which of the following statements about centrifugation are correct?
Statement 1: Particles are separated from a solution according to their size.
Statement 2: Particles are not separated from a solution according to their shape.
a) True, False
b) True, True
c) False, True
d) False, False

Answer: a
Clarification: Centrifugation is a process of separating substances which involves the centrifugal force. The particles are separated from a solution according to their size, shape, density, the viscosity of the medium and rotor speed.

250+ TOP MCQs on Membrane Separators and Answers

Food Processing Unit Operations Multiple Choice Questions on “Membrane Separators”.

1. What is pervaporation?
a) Process to separate a volatile liquid from a non-volatile liquid
b) Process to mix a volatile liquid from a non-volatile liquid
c) Process to a evaporate a non-volatile liquid
d) Process to separate water molecules from a non-volatile liquid
Answer: a
Clarification: Pervaporation is a process to separate a volatile from a non-volatile liquid. The driving force is a vacuum on the gaseous side of the membrane. It is a tool for separation of liquid mixtures.

2. Which method is used for removing hardness?
a) Nanofiltration
b) Pervaporation
c) Electrodialysis
d) Reverse Osmosis
Answer: a
Clarification: Nano filtration is used for removing hardness. It removes organic compounds and selected salts at the lower pressure than RO system. It separates at the molecular level, removing all suspended solids and most dissolved solids.

3. Which method is used separation of azeotrope mixtures?
a) Nano filtration
b) Pervaporation
c) Electro dialysis
d) Reverse Osmosis
Answer: b
Clarification: Pervaporation is a process to separate a volatile from a non-volatile liquid. The driving force is a vacuum on the gaseous side of the membrane. It is a tool for separation of liquid mixtures.

4. Which of the following uses aromatic polyamide as membrane?
a) Gas separation
b) Pervaporation
c) Electro dialysis
d) Reverse Osmosis
Answer: d
Clarification: Reverse Osmosis uses aromatic polyamide as membrane where it is used in separation of salts and micro-solutes from solutions.

5. Which of the following statements about electro dialysis are correct?
Statement 1: Cation and anion exchange membrane is used.
Statement 2: The membrane is made of polymers & co-polymers.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: a
Clarification: Cation and anion exchange membrane is used in electro dialysis where the membrane is made of sulfonated cross-linked polystyrene and is used in desalting the water.

6. What is other name for polymeric membrane?
a) Organic membrane
b) Inorganic membrane
c) Cation and anion membrane
d) Neutral charge membrane
Answer: a
Clarification: Polymeric membranes are also known as organic membranes. In order of the coarsest separation to the finest are microfiltration, ultrafiltration, nanofiltration and reverse osmosis.

7. What is flux rate for filters?
a) Ratio of flow to the membrane area
b) Ratio of concentration to the membrane area
c) Ratio of membrane area to the flow of the solution
d) Ratio of viscosity to the membrane area
Answer: a
Clarification: A membrane’s flux is defined as ratio of flow to the membrane area. It is used for calculating scalability. Ultrafiltration membranes are used in the purification of expensive biomolecules.

8. What is membrane processing?
a) Process that concentrates and separates without the use of heat
b) Process that removes dust without the use of heat
c) Process that remove water without the use of heat
d) Process that remove alcohol without the use of heat
Answer: b
Clarification: Membrane processing concentration and separation without the use of heat. Particles are separated on the basis of size of the molecules and shape with the help of pressure gradient and uses semi-permeable membranes.

9. What are cleaning techniques for the removal of membrane fouling?
a) Air flushing and chemical flushing
b) Alcohol flushing and chemical flushing
c) Air flushing and alcohol flushing
d) Air flushing
Answer: a
Clarification: There are various cleaning techniques to remove membrane fouling. These are forward flushing, backward flushing, air flushing and chemical cleaning.

10. Which of the following is used to remove yeast?
a) Nano filtration
b) Micro filtration
c) Electro dialysis
d) Reverse Osmosis
Answer: b
Clarification: Micro filtration is used for removing yeast, E- coli and mist droplets. Reverse Osmosis and nano filtration is used for removing inorganic compounds.

250+ TOP MCQs on Freeze Drying and Answers

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

1. What is alternative name for freeze drying?
a) Lyophilisation
b) Cold pasteurization
c) Irradiation
d) Liposuction
Answer: a
Clarification: The freeze drying is also known as lyophilisation where a low temperature dehydration process takes place. This involves 1.Freezing the product 2. Lowering the pressure and then removing the ice by the sublimation process.

2. What is cryodesiccation?
a) Freeze drying
b) Cold pasteurization
c) Irradiation
d) Dehydration
Answer: a
Clarification: The freeze drying is also known as cryodesiccation. In this process, dehydration takes place at a very low temperature. This is divergence to the dehydration by all the conservative methods that vaporize water using the heat.

3. During the primary drying phase in freeze drying, What is necessary to calculate amount of heat required?
a) By using latent heat of sublimation
b) By using latent heat of vapourization
c) By using enthaply
d) By using specific heat
Answer: a
Clarification: During the primary drying phase in freeze drying, the pressure is lowered and heat is given to the product for the ice sublimation. The amount of heat necessary is calculated using the latent heat of sublimation of the sublimating molecules.

4. Which of the following governs the process in secondary drying in freeze drying?
a) Latent heat of sublimation
b) Latent heat of vapourization
c) Enthaply
d) Adsorption isotherms
Answer: d
Clarification: The secondary drying phase of the freeze-drying process is overseen by the adsorption isotherms of the material. In this phase, the temperature is raised greater than in the primary drying phaseto disrupt any physicochemical interfaces that have formed between the frozen material and water molecules.

5. At what point the ice crystal formation takes place?
a) When the material is cooled below itstriple point
b) When the material is cooled below its freezing point
c) When the material is cooled below its dew point
d) When the material is cooled above its triple point
Answer: a
Clarification: During the freezing stage, the product is cooled below its triple point, this is achieved to ensure that melting does not takes place. Triple point is the lowest temperature at which the liquid, solid and gas stages of the material can coexist.

6. What is the main advantage of annealing?
a) It is done to achieve largeice crystals
b) It is done to achieve smallice crystals
c) It is done to achieve microscopicice crystals
d) It is done to achieve mixture of large and small ice crystals all
Answer: a
Clarification: The large ice crystals promote faster removal of water vapor due to formation of a network within the product during sublimation. Therefore annealing is done to achieve larger crystals where the product is slowly frozen.

7. Which of the following is known to result in the highest quality of foods amongst all drying techniques?
a) Freeze drying
b) Cold pasteurization
c) Osmotic dehyradtion
d) Evaporation
Answer: a
Clarification: Freeze drying produces highest quality of foods amongst all other drying techniques. This is mainly due to structural integrity and preservation of flavors of the product during the freezing process.

8. How long does freeze drying take?
a) 10 to 40 hours
b) 20 to 40 hours
c) 30 to 50 hours
d) 5 to 20 hours
Answer: c
Clarification: It takes between 20 to 40 hours to complete the process. Food type, quantity, thickness affects the freeze-dry cycle. Products like peas, meat, corn dry quickly whereas squash can take longer.

9. What foods cannot be freeze dried?
a) Foods with high fiber content
b) Foods with high Vitamin B12 content
c) Foods with high protein content
d) Foods with high fat content
Answer: d
Clarification: Most of the foods are suitable for freeze drying like fruits, vegetables, dairy products, meat, dry liquids like soup or yogurt and instant coffee. Foods with high fat are not suitable for freeze drying as the fat melts damages the equipment.

10. Who discovered freeze drying?
a) Jacques-Arsened’Arsonval
b) Charles Chamberland
c) Willis Carrier
d) Clarence Birdseye
Answer: a
Clarification: Jacques-Arsened’Arsonval discovered freeze drying. Charles Chamberl and developed the first pressure steam sterilizer. Willis Carrier invented the chillers. Clarence Birdseye developed processes for freezing fish based on quick freezing.

250+ TOP MCQs on Heat Convection and Answers

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

1. Which of the following example explain convection?
a) The heat from a hot liquid makes the cup itself hot
b) Walking on the beach on a hot summer day will warm the feet
c) A metal spoon becomes hot from the boiling water inside the pot
d) The formation of sea and land breeze
Answer: d
Clarification: The formation of sea and land breeze is an example of convection. During a day, the sun the sun warms the ground and sea water. Since the ground has lower specific heat compared to water and so its temperature increases more than the temperature of the water. The air above ground is heated thus forming a rise in the convection currents and the cool air from over sea flows towards shore. This is called as sea breeze. Similarly in the evening, ground cools faster than water and therefore breeze flows from shore to sea.

2. Which law governs the thermal convection?
a) Fourier’s law
b) Pascal law
c) Newton’s law
d) Stefan-Boltzmann Law
Answer: c
Clarification: Newton’s law governs the thermal convection especially in convection cooling. It states that rate of heat loss of a body is directly proportional to the temperature difference between the body and its surroundings.

3. ___________ is the transfer of thermal energy through the movement of a liquid or gas.
a) Convection
b) Conduction
c) Radiation
d) Evaporation
Answer: a
Clarification: Convection is the transfer of thermal energy through the movement of a liquid or gas.Convection can be defined as the heat transfer by the movement of a fluid between areas of temperature difference.

4. Is conduction faster than convection?
a) True
b) False
Answer: b
Clarification: Convection is faster than conduction. In convection the medium in which heat transfer takes place is in motion whereas the heat transfer through conduction takes place by collision between the atoms.

5. Are these statements about the thermal convection true?
Statement 1: Thermal convection depends on temperature gradient.
Statement 2: It does not depend on relative motion of the fluid.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: a
Clarification: The properties of heat transfer by the convection between a body and its surrounding are 1. The convection takes place when there is temperature difference between two medium. 2. It depends on the relative motion of the fluid as convection takes place only when the medium has movement.

6. _________ is the currents produced only by temperature difference.
a) Natural convection
b) Forced convection
c) Conduction
d) Radiation
Answer: a
Clarification: Natural convection is a type of convection where the heat transfer takes place only due to density difference that leads to the temperature difference in the fluid. The gravitational force is the main driving force in the natural convection.

7. In __________, fluid is forced to flow over a surface or in a tube by external means.
a) natural convection
b) forced convection
c) conduction
d) radiation
Answer: b
Clarification: Forced convection is a mechanism of heat transfer in which fluid motion is produced by an external source such as ceiling fan, a pump and suction device. It creates uniform and comfortable temperature throughout the medium.

8. Convective heat transfer coefficients for air under natural convection is __________
a) 0.5 – 1000 (W/(m2K))
b) 50 – 3000 (W/(m2K))
c) 10 – 1000 (W/(m2K))
d) 50 – 10000 (W/(m2K))
Answer: a
Clarification: Convective heat transfer coefficients for air under natural convection is 0.5 – 1000 (W/(m2K)). For liquids under natural convection is 50 – 3000 (W/(m2K)). For air under forced convection it is 10 – 1000 (W/(m2K)). For liquids under forced convection it is 50 – 10000 (W/(m2K)).

9. Convective heat transfer coefficients for condensing water vapor is __________
a) 0.5 – 1000 (W/(m2K))
b) 5 – 100 (W/(m2K))
c) 10 – 1000 (W/(m2K))
d) 50 – 10000 (W/(m2K))
Answer: b
Clarification:A convective heat transfer coefficient for condensing water vapor is 5 – 100 (W/ (m2K)). It is proportionality constant between heat flux and temperature difference that plays an important factor as driving force for the flow of heat.

10. Convective heat transfer coefficients for liquid under forced convection is __________
a) 0.5 – 1000 (W/(m2K))
b) 50 – 3000 (W/(m2K))
c) 10 – 1000 (W/(m2K))
d) 50 – 10000 (W/(m2K))
Answer: d
Clarification: Clarification: Convective heat transfer coefficients for air under natural convection is 0.5 – 1000 (W/(m2K)). For liquids under natural convection is 50 – 3000 (W/(m2K)). For air under forced convection it is 10 – 1000 (W/(m2K)). For liquids under forced convection it is 50 – 10000 (W/(m2K)).