Category: Food Processing Unit Operations Objective Questions

250+ TOP MCQs on Basic Drying Theory and Answers

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

1. Lyophilization is also known as ____________
a) freezedrying
b) sundrying
c) tunneldrying
d) mechanicaldrying
Answer: a
Clarification: Lyophilization is also called as freeze drying. It is a process where biological material is preserved by removing the water from sample. It is a twostep process, first the sample is freeze and then dry it under a vacuum at low temperatures.

2. What is a triple point of pure water?
a) -0.01°C
b) 0.01°C
c) 0.1°C
d) -0.1°C
Answer: b
Clarification: The triple point of pure water is at 0.01°C. The triple point is the condition in which the temperature and pressure of all three phases (gas, liquid and solid) can coexist in equilibrium.

3. Phase diagram is a graphical representation of the ________ states of a substance under different conditions of temperature and pressure.
a) physical
b) chemical
c) electromagnetic
d) mechanical
Answer: a
Clarification: Phase diagram is a graphical depiction of the physical conditions of a matter under different conditions of temperature and pressure. It has temperature on the x-axis and pressure on the y-axis.

4. __________ diagrams represent the phase behavior of mixtures containing three components.
a) Ternary phase
b) Tertiary phase
c) Tri phase
d) Term phase
Answer: a
Clarification: The ternary phase represents the behavior of three components in a mixture with a triangular diagram. These diagrams provide the data which is precise and accurate of the various components.

5. The effect of ______on the system is seen only as a phase change.
a) Latent heat
b) Specific heat
c) Enthalpy
d) Entropy
Answer: a
Clarification: Latent heat can be defined as the heat that is released or absorbed by a system during constant temperature process. The effect is seen only as a phase change like boiling of water or the melting of ice.

6. The term triple point was coined by ___________
a) Rudolf Clausius
b) Thomas Young
c) Joseph Black
d) James Thomson
Answer: d
Clarification: Rudolf Clausius invented the term entropy. Thomas Young invented the term enthalpy. Joseph Black invented the term latent heat. The term triple point was coined by James Thomson.

7. What is the critical point of water?
a) 374°C
b) 157.5°C
c) 31.0°C
d) 240.9°C
Answer: a
Clarification: The critical point of water is 374°C. The critical point of sulphuric acid is 157.5°C. The critical point of supercritical carbon dioxideis 31.0°C. The critical point of ethanol is 240.9°C.

8. What are factors depending on rate of drying?
a) Initial moisture content of the product
b) Composition of raw material
c) Temperature, relative humidity
d) Initial moisture content, composition, temperature, relative humidity of the product.
Answer: d
Clarification: Drying rate is defined as the mass of water removed per unit time per unit area. It depends on initial moisture content, composition, temperature, relative humidity of the product, Size, shape and arrangement of stacking of the raw material.

9. Who discovered critical point?
a) Joseph Black
b) Charles Cagniard de la Tour
c) Henri Becquerel
d) Stephen Gray
Answer: b
Clarification: Joseph Black discovered latent heat. Charles Cagniard de la Tour discovered critical piont. Henri Becquerel discovered radiation. Stephen Gray discovered electrical conduction.

10. Does boiling point increase with pressure?
a) True
b) False
Answer: a
Clarification: At higher altitudes, the atmospheric pressure is much lower therefore the boiling point is also lower. The boiling point depends on pressure up to the critical point. It is directly proportional to the pressure. At the critical point the gas and liquid properties are same.

250+ TOP MCQs on Fluid Statics & Fluid Dynamics and Answers

Food Processing Unit Operations Multiple Choice Questions on “Fluid Statics and Fluid Dynamics”

1. The force per unit area in a fluid is called as __________
a) differential pressure
b) fluid pressure
c) dynamic pressure
d) absolute pressure

Answer: b
Clarification: The force per unit area in a fluid is called as fluid pressure. Since the fluid does not have any shape, the forces can be exerted in all directions such as gravitational force, external force on the fluid.

2. Which principle explains the buoyant force of a fluid?
a) Archimedes principle
b) Pascal’s principle
c) Bernoulli’s Principle
d) Newton’s second law of motion

Answer: a
Clarification: Archimedes principle states that the object partially or fully submerged in a fluid will experience a buoyant force which is equal to the fluid weight in which object is displaced.

3. Hydraulic system works on the basis of ____________
a) Archimedes principle
b) Pascal’s principle
c) Bernoulli’s Principle
d) Newton’s second law of motion

Answer: b
Clarification: Hydraulic system works on the basis of Pascal’s principle. This principle states that when pressure is applied to a closed system of fluid, the pressure is transmitted to every part of the fluid and also to the walls of the container in which fluid is enclosed.

4. Are these statements about the Fluid mechanics true?
Statement 1: Fluid mechanics is a branch in chemistry that involves study of fluids.
Statement 2: Fluid mechanics can be divided into 2 major categories.
a) True, False
b) True, True
c) False, True
d) False, False

Answer: c
Clarification: Fluid mechanics is a branch in physics that involves study of fluids such as liquids, plasma and gases. Fluid mechanics can be divided into 2 major categories. They are fluid statics (study based on fluids at rest) and fluid dynamics (study based on fluids in motion).

5. Which principle is used in designing the wings of airplanes?
a) Archimedes principle
b) Pascal’s principle
c) Bernoulli’s Principle
d) Newton’s second law of motion

Answer: c
Clarification: Bernoulli’s Principle is used in designing the wings of airplanes. According to the law of aerodynamics called Bernoulli’s principle, fast moving air has low pressure than slow moving air which has high pressure, so therefore pressure above wings is lower compared to pressure below the wings and this creates the lift in the plane that powers it to fly upwards.

6. Which of the following statements about applications of Pascal law in daily life are precise?

  • Statement 1: It is used in hydraulic pumps and hydraulic press.
  • Statement 2: It is not used in braking system in the vehicles.

a) True, False
b) True, True
c) False, True
d) False, False

Answer: a
Clarification: The applications of Pascal law in daily life is that it is used in hydraulic pumps and hydraulic press. It is also commonly used in in braking system in the vehicles where a fluid called brake fluid is used to transmit the pressure from the brake pedal to the all the vehicle wheels.

7. Who is the father of fluid mechanics?
a) Stephen Prokofievitch Timoshenko
b) Ludwig Prandtl
c) Singh Kapany
d) Samuel Colville Lind

Answer: b
Clarification: Ludwig Prandtl is called as the father of fluid mechanics. Stephen Prokofievitch Timoshenko is father of engineering mechanics. Singh Kapany is the father of fiber optics. Samuel Colville Lind is father of chemical kinetics.

8. What are applications of fluid statics?
a) Barometers, anemometer
b) Manometers, anemometer
c) Manometers, hygrometer
d) Manometer, barometers

Answer: d
Clarification: Manometer, barometers are used in measuring the pressure of the fluid based on the fluid state mechanism. Anemometer is used in measuring the wind speed and also the direction of the wind. Hygrometer is used to measure the humidity.

9. Fluid in static condition has shear stress.
a) True
b) False

Answer: b
Clarification: A fluid in static condition has no shear stress. The shear stress is known as force per unit area that is acting parallel to the inconsiderable surface element. It is mainly caused by the friction between fluid molecules due to viscosity of the fluid.

10. What causes the turbulence in fluid flow?
a) Kinetic energy
b) Pressure
c) Force
d) Potential energy

Answer: a
Clarification: During the flow of the fluid, the excessive kinetic energy that is present in the fluid causes the turbulence which overpowers the resistance of fluid. The turbulence is reduced by reducing Reynolds number.

250+ TOP MCQs on Size Reduction – Grinding Principles and Laws and Answers

Basic Food Processing Unit Operations Questions and Answers on “Size Reduction – Grinding Principles and Laws”.

1. What is the principle of particle size distribution?
a) Based on light scattering
b) Based on the pressure exerted by particles
c) Based on the pressure exerted by equipment
d) Based on the temperature exerted by particles
Answer: a
Clarification: The particle size distribution is based on the principle that when a ray of light is scattered by a set of particles, then the angle of scattering of light is indirectly proportional to the size of the particle.

2. What is Kick’s law?
a) Amount of energy required to tear the given material
b) Amount of energy required to crush the given material
c) Amount of energy required to compress the given material
d) Amount of energy required to break the given material
Answer: b
Clarification: The kick’s law is defined as the amount of energy required to crush a given amount of material to a specified fraction of its original size is the same, regardless of the original size.

3. What is Rittinger’s law?
a) Energy required is directly proportional to the increase in surface area
b) Energy required is indirectly proportional to the increase in surface area
c) Pressure required is directly proportional to the increase in surface area
d) Pressure required is indirectly proportional to the increase in surface area
Answer: a
Clarification: The Rittinger’s law is stated as the energy required for reduction in particle size of a solid is directly proportional to the increase in surface area.

4. What is Bond’s law?
a) Work required is directly proportional to the surface to volume ratio
b) Work required is indirectly proportional to the surface to volume ratio
c) Energy required is directly proportional to the surface to volume ratio
d) Energy required is directly proportional to the surface to volume ratio
Answer: a
Clarification: Bond’s law states that the work required to produce particles from large particle size is directly proportional to the square root of the surface-to-volume ratio.

5. Which of the following statements about crushing efficiency are correct?
Statement 1: It depends on surface energy created by energy.
Statement 2: Single layer particle crushing was taken to be 100% efficient.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: Crushing efficiency is defined as the ratio of surface energy created by crushing during crushing to the energy absorbed by the solid. Single layer particle crushing was taken to be 100% efficient.

6. Which of the following law determine energy requirement in size reduction?
a) Kick’s law, Bond’s law
b) Rittinger’s law, Bond’s law
c) Rittinger’s law and Kick’s law
d) Kick’s law, Bond’s law, Rittinger’s law
Answer: c
Clarification: Determination of energy required in size reduction is generally done using Kick’s law or Rittinger’s law. The Rittinger’s law is stated as the energy required for reduction in particle size of a solid is directly proportional to the increase in surface area. The kick’s law is defined as the amount of energy required to crush a given amount of material to a specified fraction of its original size is the same, regardless of the original size.

7. Which of the law is used for coarse grinding?
a) Rittinger’s Law
b) Kick’s Law
c) Bond’s Law
d) Bond’s Law, Rittinger’s Law, and Kick’s Law
Answer: b
Clarification: Kick’s law is used for coarse grinding when the size ratio of original material to end materials is 8:1. The kick’s law is defined as the amount of energy required to crush a given amount of material to a specified fraction of its original size is the same, regardless of the original size.

8. Which of the law is used for fine grinding?
a) Rittinger’s Law
b) Kick’s Law
c) Bond’s Law
d) Bond’s Law, Rittinger’s Law, and Kick’s Law
Answer: a
Clarification: Rittinger’s Law is defined as the energy required for reducing the size of the solid particle is directly proportional to the increase in surface area. Rittinger’s Law is used for fine grinding.

9. Which of the law is used for intermediate grinding?
a) Rittinger’s Law
b) Kick’s Law
c) Bond’s Law
d) Bond’s Law, Rittinger’s Law, and Kick’s Law
Answer: c
Clarification: Bond’s law is used for intermediate grinding. Bond’s law states that the work required to produce particles from large particle size is directly proportional to the square root of the surface-to-volume ratio.

10. Are size reduction results in loss of volatiles in heat sensitive foods?
a) True
b) False
Answer: a
Clarification: Size reduction causes loss of volatiles in heat sensitive foods like spices. In wheat milling, the proteins, vitamins and minerals and other important food components are lost due to separation of the bran and aleurone layer.

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250+ TOP MCQs on Mechanism of Crystallization and Answers

Food Processing Unit Operations Multiple Choice Questions on “Mechanism of Crystallization”.

1. What is co-crystallization?
a) Parallel arrangement in crystallization
b) Catalysts
c) Cross arrangements in crystallization
d) Seeding agents
Answer: d
Clarification: Co crystallization or seedling agents are the process by which a solid forms, where the molecules are very organized and forms into a structure known as a crystal.

2. What is the mechanism of crystallization?
a) Nucleation, crystal maturation and growth
b) Nucleation and growth
c) Nucleation, growth, and crystal maturation
d) Nucleation and crystal maturation
Answer: c
Clarification: The mechanism of crystallization includes in the order of nucleation, growth and finally maturation of the crystals, thus leading to the crystalline lattice.

3. What is crystallization temperature?
a) Temperature at which the brine solution is partially saturated
b) Temperature at which the brine solution is fully saturated
c) Temperature at which the solute and solvent is fully saturated
d) Temperature at which the solute and solvent is partially saturated
Answer: b
Clarification: The thermodynamic crystallization temperature which is also called as true crystallization temperature is defined as the temperature at which the brine solution is completely saturated with respect to the least soluble salt.

4. Is crystal size controlled by temperature?
a) True
b) False
Answer: a
Clarification: Under crystal nucleation, the process follows the number of formed crystal nuclei increases with supersaturation. When the temperature of crystallization process changes therefore the crystal size is also changed.

5. Which of the following statements about evaporative crystallization are correct?
Statement 1:The process depends on evaporation of the solvent.
Statement 2:This process does not create vapor or suspension of crystals in mother liquor.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: a
Clarification: In evaporative crystallization, the process is due to the evaporation of solvent. So, therefore this process creates vapor and suspension of crystals in mother liquor. The evaporation heat is added in the captured vapor stream.

6. Who invented crystallization?
a) Jabir ibn Hayyan
b) Charles Chamberland
c) Willis Carrier
d) Clarence Birdseye
Answer: a
Clarification: Jabir ibn Hayyan invented crystallization. Charles Chamberland developed the first pressure steam sterilizer. Willis Carrier invented the chillers. Clarence Birdseye developed processes for freezing fish based on quick freezing.

7. What is special form of cooling crystallization process?
a) Freeze crystallization
b) Slow crystallization
c) Melt crystallization
d) Quick crystallization
Answer: c
Clarification: The melt crystallization is observed as a distinct form of cooling crystallization process. The main difference with cooling crystallization from other method is the nonexistence of solvents which suggests that this process is operated near to the melting point of the pure component.

8. Which process is called as a counter-current cascade?
a) Fractional crystallization
b) Cooling crystallization
c) Precipitation
d) Evaporative crystallization
Answer: a
Clarification: Fractional crystallization is called as a counter-current cascade. It is used to describe a process where repeated crystallization steps. These are used to increase the purity of the product and to increase the yield of the process.

9. Which of the following statements about fractional crystallization are correct?
Statement 1: In this process, repeated crystallization takes place.
Statement 2: It increases the purity of the material.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: Fractional crystallization is used to describe a process where repeated crystallization steps. These are used to increase the purity of the product and to increase the yield of the process.

10. Is cooling crystallization is more energy friendly than evaporative crystallization?
a) True
b) False
Answer: a
Clarification: The cooling crystallization is typically more energy friendly than the evaporative crystallization. In cooling crystallization process the feed is cooled in heat exchanger, where it is situated inside the crystallizer. The crystallizer wall can be used as internal heat exchanger.

250+ TOP MCQs on Absorption Principles and Answers

Food Processing Unit Operations Multiple Choice Questions on “Absorption Principles”.

1. What is the alternative name for stripping?
a) Gas absorption
b) Gas desorption
c) Adsorption
d) Liquid desorption
Answer: b
Clarification: Gas desorption is also called as stripping. In gas desorption, the mass transfer is from the liquid phase to the gas phase. The principles for both gas absorption and gas desorption are the same.

2. What are types of absorption?
a) Physical absorption
b) Chemical absorption
c) Physical absorption and chemical absorption
d) Physical absorption, chemical absorption and microbial absorption
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. What is reactive absorption?
a) Chemical absorption
b) Physical absorption
c) Microbial absorption
d) Ion absorption
Answer: a
Clarification: When a strong base like aqueous sodium hydroxide is used as the absorbent to dissolve an acid gas, the absorption process is accompanied by a rapid and irreversible neutralization reaction in the liquid phase and the process is known as chemical absorption or reactive absorption.

4. Who invented the absorption refrigerator?
a) Albert Einstein
b) Ferdinand Carre
c) Robert Wilhelm Bunsen
d) Schuyler Skaats Wheeler
Answer: a
Clarification: Albert Einsteininvented the absorption refrigerator. Ferdinand Carreinvented an electric light regulator. Robert Wilhelm Bunsen invented the spectrometer. Schuyler Skaats Wheeler invented fans.

5. What is the principle of absorption spectroscopy?
a) Bound atoms in the ground state can absorb light of a certain wavelength
b) Free atoms in the ground state can absorb light of a certain wavelength
c) Bound atoms in the excited state can absorb light of a certain wavelength
d) Free atoms in the ground state can absorb radiation energy of a certain wavelength
Answer: b
Clarification: Absorption spectroscopy is based upon the principle that free atoms in the ground state can absorb light of a certain wavelength. Absorption is specificfor each element, and thus, no other elements can absorb this wavelength.

6. Which of the following factors that affect the selection of absorbent?
a) Viscosity should be low
b) Viscosity should be high
c) Low pressure drops
d) Low pressure drops and viscosity should be low
Answer: d
Clarification: Absorbent is defined as the material having ability to absorb another substance. Absorbents should usually be having low pressure drops in absorption tower and low viscosity for rapid absorption rates.

7. Which of the following is not an example for absorption?
a) Reaction of oxygen by fermentation broths
b) Removal of carbon dioxide from water-gas by absorption in water or in solutions of alkalis or amines
c) Reaction of hydrogen by petroleum fractions in processes to remove sulphur as hydrogen sulphide.
d) Liquid ammonium in air
Answer: d
Clarification: Examples of absorption are i. Absorption of nitrous gases in water or nitric acid, during nitric acid manufacture. ii. Removal of carbon monoxide from water-gas by absorption in solutions of copper complexes. iii. The production of hypochlorite by absorbing chlorine through alkaline solutions. iv. Absorption of hydrogen by petroleum fractions in processes to remove sulphur as hydrogen sulphide.

8. Which of the following statements about chemical absorption are correct?
Statement 1: Chemical reaction between the absorbed and the absorbing substances.
Statement 2: Depends upon the stoichiometry of the reaction.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: When the absorption is reactive then it is called as chemical absorption. There will be a chemical reaction between the absorbed and the absorbing substances. It depends on the stoichiometry of the reaction and the concentration of its reactants.

9. What is law behind absorption?
a) Nernst’s distribution law
b) Henry’s law
c) Raoult’s law
d) Dalton’s law
Answer: a
Clarification: The Nernst’s distribution law also called as Distribution law. This law governs the distribution of solute between two non-miscible solvents. It is important to note that it should not undergo dissociation or association.

10. Which of the following statements about physical absorption are correct?
Statement 1: Example for physical absorption is the absorption of carbon dioxide into water.
Statement 2: Polar interactions between water and the molecules of the solid play an important role in physical absorption.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: When the absorption is non-reactive then it is called as physical absorption. Polar interactions between water and molecules of solid play an important role in physical absorption. Example for physical absorption is the absorption of carbon dioxide into water. The hydrophilic solids readily absorb water.

250+ TOP MCQs on Heat Transfer Applications – Chilling and Freezing and Answers

Food Processing Unit Operations Multiple Choice Questions on “Heat Transfer Applications – Chilling and Freezing”.

1. Who invented chillers?
a) Louis Pasteur
b) Charles Chamberland
c) Willis Carrier
d) Clarence Birdseye
Answer: c
Clarification: The pasteurization process was developed by Louis Pasteur. Charles Chamberland developed the first pressure steam sterilizer. Willis Carrier invented the chillers. Clarence Birdseye developed processes for freezing fish based on quick freezing.

2. _________ is used for cooling of products, mechanisms and factory machinery under control temperature.
a) Chiller
b) Ice
c) Alcohol
d) Ice or alcohol according to the product
Answer: a
Clarification: Chillers are used for cooling of products, mechanisms and factory machinery under control temperature. These follow absorption refrigerant cycle or vapor compressionfor cooling a fluid. The basic principle is that heat always flows from hot to cold.

3. What is the ideal chilled water temperature?
a) 42°F
b) 52°F
c) 49°F
d) 50°F
Answer: a
Clarification: 42°F is the ideal chilled water temperature. The temperature of chilled water can range from 35 to 45 °F (2 to 7 °C), depending upon requirements.

4. __________ invented the quick freezing method in 1924.
a) Clarence Birdseye
b) Charles Chamberland
c) Willis Carrier
d) Clarence Birdseye
Answer: a
Clarification: Clarence Birdseye invented the quick freezing method. Charles Chamberland developed the first pressure steam sterilizer. Willis Carrier invented the chillers. Clarence Birdseye developed processes for freezing fish based on quick freezing.

5. ______ chillers are also called as centrifugal chiller type refrigeration systems.
a) Low-pressure
b) Low-temperature
c) Low-velocity
d) High-pressure
Answer: a
Clarification: Low-pressure chillers are also called as centrifugal chiller type refrigeration systems. It works under vacuum in the evaporator section of the system. If there is any leaks in the low pressure portions of the system, it will draw in the atmospheric air and moisture from the surroundings.

6. ________ chiller is powered by a heat source like steam and uses no moving parts.
a) Absorption
b) Reciprocating
c) Centrifugal
d) Screw driven
Answer: a
Clarification: In absorption chillers, the refrigerant is absorbed by a liquid sorbent. The refrigerant used are water and ammonia and liquid sorbents arelithium bromide or water. At high temperatures, the refrigerant is desorbed from solution.

7. ________ chillers are volume displacement units.
a) Absorption
b) Reciprocating
c) Centrifugal
d) Screw driven
Answer: c
Clarification: Centrifugal chillers are volume displacement units. The advantages are compact size, high operational efficiency at full load. It is not suitable for air cooled condenser options and requires cooling water tower and water.

8. Freezer burn is a condition that occurs when frozen food has been damaged by ___________
a) dehydration
b) oxidation
c) dehydration and oxidation
d) dehydration and reduction
Answer: c
Clarification: Freezer burn occurs when frozen food is damaged by dehydration and oxidation. It is normally due to improper of storage of food. Therefore, it should be securely wrapped in air-tight packaging to prevent oxidation and dehydration. The food appears grayish brown leathery spots on the frozen foods.

9. _______ is used to freeze particulate foods like peas, cut corn.
a) Fluidized bed freezer
b) Plate freezer
c) Cryogenic freezers
d) Belt freezer
Answer: a
Clarification: Fluidized bed freezer is used to freeze particulate foods like peas, cut corn. The foods are placed on a mesh and moved through a freezing zone where cold air in upward direction is directed through the mesh belt and the food particulates begin to float. This leads to uniform freezing in all directions.

10. _______ is used to freeze food at a tremendously fast rate.
a) Fluidized bed freezer
b) Plate freezer
c) Cryogenic freezers
d) Belt freezer
Answer: c
Clarification: Cryogenic freezing is used to freeze food at a tremendously fast rate. The food is moved through a spray of liquid nitrogen. It can also be directly immersed in liquid nitrogen. The liquid nitrogen boils at a temperature of −196 °C around the food and thus extracts a huge amount of heat at faster pace.