Category: Food Processing Unit Operations Objective Questions

250+ TOP MCQs on Unit Systems – Dimensional Analysis and Answers

Food Processing Unit Operations Interview Questions and Answers on “Unit Systems – Dimensional Analysis”.

1. The analytical procedure of studying physical phenomena in variables, and corelating them to obtain a dimensionless group is known as ________
a) Dimensional constants
b) Dimensional homogeneity
c) Dimensional variable
d) Dimensional analysis
Answer: d
Clarification: The study of variables corelated to their physical phenomena and studying them analytically to solve problems refers to Dimensional analysis. If the equation expresses a proper relationship between the both, then dimensional homogeneity is obtained and the varying quantities are called dimensional variables, whereas the values normally held constant, are called dimensional constants.

2.The occurrence of closeness of measured values towards each other is known as ______
a) Accuracy
b) Precision
c) Measurement
d) Dimensional Analysis
Answer: b
Clarification: Precision is the closeness of more than one values towards each other. On the other hand, Accuracy is the closeness of the measured value to the known or standard value.

3. What are the principles for ensuring the consistency of an equation through dimensional analysis?
Statement I: The sum of all exponents of any dimension (e.g., mass), should be the same on both sides of the equation.
Statement II: An exponent must itself be a pure / dimensionless number.
Statements III: The magnitude of the exponent does not necessarily have to be a whole number.
a) I & II
b) II
c) III
d) I, II & III
Answer: d
Clarification: To verify the correctness of any given equation through dimensional analysis, we need to ensure that the sums of all exponents relating to any given dimension are equal on both sides of the equation. The exponent should be dimensionless or in other words, a pure number, although its magnitude does not necessarily have to be a whole number.

4. State True or False.
Statement I: Through dimensional analysis of Physical quantities we can verify whether an equation is correct or not.
Statement II: With dimensional analysis we can derive a relation between various physical quantities.
a) True, True
b) False, False
c) True, False
d) False, True
Answer: a
Clarification: The main purpose of using dimensional analysis, is to verify whether a given equation is correct or not. It also assists the derivation of a relationship between various physical quantities.

5. What are the dimensions of Energy?
a) (MLT-2)
b) (M-1L3T-2)
c) (M L2T-2)
d) (LT-2)
Answer: c
Clarification: Energy is also known as work done, for which the formula is the product of force into displacement, i.e. Work = Force (mass x acceleration) X Displacement (in meters). We know that the dimensions for force and displacement are (MLT-2) and (L) respectively. Therefore, the dimensions for Energy are (M L2T-2).

6. In Fluid dynamics, Reynold’s number is a dimensionless number. True or False?
a) False
b) True
Answer: b
Clarification: In fluid dynamics, inertial forces are very important and the ratio of these inertial forces to viscous, pressure, gravity, surface tension and compressibility forces lead to formation of fundamental dimensionless groups. Reynold’s number is the ratio of inertial force to viscous force and is thus, dimensionless.

7. What is the ratio of inertial force to gravitational force known as?
a) Weber number
b) Froude number
c) Reynold’s number
d) Euler Number
Answer: b
Clarification: Fr or Froude number is the ratio of inertial force to gravitational force. Its formula is Fr =(frac{V}{sqrt{g.L}}) . On the other hand, Weber number is the ratio of inertial force to surface tension and Reynold’s number is the ratio of inertial force to viscous force.

8. Which dimensionless number is denoted by the equation Pr =(frac{μC_p}{k}) ?
a) Prandtl number
b) Weber number
c) Reynold’s number
d) Froude number
Answer: a
Clarification: Prandtl number is a dimensionless number used to determine heat convection. It is the ratio of the amount of heat dissipated to the amount of heat conducted. Whereas, Froude number is the ratio of inertial force to gravitational force, Weber number is the ratio of inertial force to surface tension and Reynold’s number is the ratio of inertial force to viscous force.

9. Is Plane angle a derived unit?
a) True
b) False
Answer: a
Clarification: There are seven basic or standard units. Plane angle is one of them, like Mass, Length, Time, etc. It is measured in radians and denoted by ‘rad’.

10. What is the ratio of inertial force to compressibility force and is also the key parameter, characterizing compressibility effects in fluids?
a) Froude number
b) Strouhal number
c) Mach number
d) Weber number
Answer: c
Clarification: Mach number (M) is the ratio of inertial force to compressibility force and is used in problems where fluid compressibility is important. Strouhal number, on the other hand, is important in unsteady, oscillating flow problems. Froude number is the ratio of inertial force to gravitational force whereas, Weber number is the ratio of inertial force to surface tension.

250+ TOP MCQs on Filtration at Constant Volumetric Flow and Answers

Food Processing Unit Operations Multiple Choice Questions on “Filtration at Constant Volumetric Flow”.

1. How is flow rate calculated?
a) Driving force + total resistance
b) Driving force – total resistance
c) Driving force x total resistance
d) Driving force / total resistance
Answer: d
Clarification: Flow rate is defined as the volume of fluid which passes per unit time. The flow rate in the filtration can be calculated as the ratio of the driving force to total resistance offered by the filter cake.

2. How does the increase in filter cake affect the flow rate?
a) Increase then decrease
b) Increase
c) Decrease
d) Does not depend
Answer: b
Clarification: A filter cake is formed by the substances that are retained on a filter. The filter cake grows in the course of filtration. With increasing layer thickness, the flow resistance of the filter cake increases.

3. What law is applicable when the flow rate is laminar?
a) Poiseuille’s law
b) Newton’s law
c) Gauss’s law
d) Dalton’s law
Answer: a
Clarification: Filtration rate is directly proportional to the difference in pressure and inversely proportional to the fluid viscosity and to the hydraulic resistance of the cake and filter medium.

4. What is the relationship between temperature and filtrate volume?
a) Directly proportional
b) Indirectly proportional
c) Equal
d) Does not depend
Answer: a
Clarification: An increase in temperature increases the filtrate volume. This reduces the viscosity of the filtrate and therefore the filtrate volume also increases.

5. What is the demerit of increase in filtrate volume during filtration?
a) Solvent recovery
b) Time consumption
c) Efficiency
d) Power consumption
Answer: a
Clarification: Disadvantages of increased filtrate volume are solvent recovery and flammability issues. The use of surfactants such as sulphosuccinates can increase filtration rates and reduce equilibrium cake moisture during gas de-liquoring.

6. What is constant rate filtration?
a) Q=dV/dt is kept constant
b) Q=dt/dV is kept constant
c) Q=dp/dt is kept constant
d) Q=dp/dV is kept constant
Answer: a
Clarification: The constant rate filtration Q=dV/dt is kept constant. The pressure drop is to be increased in order to overcome the increasing opposition due to cake build-up.

7. Which of the following is not the factor that controls the rate of filtration?
a) Particle Size of Solids.
b) Ratio of slimes to coarser particles.
c) Temperature
d) Feed solids concentration.
Answer: c
Clarification: Factors that control the rate of filtration are particle size of solids, ratio of slimes to coarser particles, filter aids, feed solids concentration, filter thickening, slurry pH and flocculation of fine solids

8. Does viscosity affect filtration?
a) True
b) False
Answer: a
Clarification: As concentration of the solids increases in the suspension, there is an increase in thickness of the filter cake. The filtration rate mainly depends on the viscosity of the slurry. Due to presence of solids in the suspension, a resistance force called viscosity is taken into consideration during the filtration.

9. What is the relationship between concentration and filtrate volume?
a) Directly proportional
b) Indirectly proportional
c) Equal
d) Does not depend
Answer: b
Clarification: Filtration rate is inversely proportional to concentration of the solution. When the solids are present in a very low concentration the filtration is high and rapid.

10. What is rate of filtration?
a) Pressure of filtrate per unit volume
b) Volume of filtrate collected per unit time
c) Pressure of filtrate per unit time
d) Volume of solution per unit time
Answer: b
Clarification: As the filter medium is penetrable only to the fluid, it retains the solid particles and permits only the fluid to pass through medium which is collected as the filtrate. The volume of filtrate collected per unit time is known as the rate of filtration.

250+ TOP MCQs on Principles of Crystallization and Answers

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

1. What is meant by crystallization?
a) Concentration of atoms into a highly structured form
b) Solidification of atoms into a highly structured form
c) Solidification of solution
d) Concentration of solution
Answer: b
Clarification: Crystallization is solidification of atoms into a highly structured form called a crystal. It is the solid-liquid separation and purification technique where mass transfer occurs from the liquid solution to a pure solid crystalline phase.

2. When is supersaturation attained?
a) When the solvent contains more solute
b) When the solute contains more solvent
c) When the solvent contains less solute
d) When the solute contains less solvent
Answer: a
Clarification: Supersaturation is defined as the state in which the solvent contains more dissolved solids (solute) than can usually be accommodated at that temperature.

3. Which of the following is crystallization?
a) Solid-solid separation
b) Solid-liquid separation
c) solid-gas separation
d) Liquid- gas separation
Answer: b
Clarification: Crystallization is solidification of atoms into a highly structured form called a crystal. It is the solid-liquid separation and purification technique where mass transfer occurs from the liquid solution to a pure solid crystalline phase.

4. What is purpose of recrystallization?
a) To purify chemicals
b) To dissolve crystals
c) Continuous process of crystallization
d) To clean crystallizers
Answer: a
Clarification: Recrystallization is a technique used to purify chemicals. By dissolving both impurities and a compound in an appropriate solvent, either the desired component or impurities can be removed from the solution, parting the other behind.

5. How does concentration affect crystallization?
a) Increase in concentration leads to large crystals
b) Decrease in concentration leads to large crystals
c) Increase in concentration leads to small crystals
d) Decrease in concentration leads to small crystals
Answer: a
Clarification: When the water evaporates faster the concentration increases. The larger crystals can accommodate larger the surface where more molecules can be added.

6. What are crystallization techniques?
a) Gradual cooling and diffusion
b) Diffusion and sharp cooling
c) Gradual cooling and sharp cooling
d) Sharp cooling and crystallization
Answer: a
Clarification: Crystallization is a technique used to for solids purification. The two common methods of crystallization are gradual cooling and diffusion.

7. Why is a supersaturated solution unstable?
a) Concentration is higher than equilibrium concentration
b) Concentration is lower than equilibrium concentration
c) Concentration is equal to equilibrium concentration
d) Contains impurities
Answer: a
Clarification: The solute in a supersaturated solution is present in concentration higher than equilibrium concentration; therefore the supersaturated solutions are unstable.

8. What are factors affecting crystallization?
a) Degree of agglomeration
b) Crystal shape
c) Particle size distribution
d) Particle size distribution, crystal shape, degree of agglomeration
Answer: d
Clarification: The factors affecting crystallization are particle size distribution, crystal shape, degree of agglomeration, purity and caking behavior.

9. How does temperature affect nucleation?
a) When temperature increases the nucleation decreases
b) When temperature increases the nucleation increases
c) Nucleation is not dependent on Temperature
d) When temperature increases the nucleation increases and then decreases
Answer: a
Clarification: When the nucleation decrease drastically as the temperature increases. Thus, the decrease in nucleation at higher temperature leads to the decrease in supersaturation.

10. Is crystallization a chemical change?
a) True
b) False
Answer: b
Clarification: In crystallization, there is no chemical change occurs in the chemical compound as there is no new products are created. Therefore, crystallization is a physical change.

250+ TOP MCQs on Absorption Mechanisms and Answers

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

1. What is the principle behind paper chromatography?
a) It is based on partition chromatography
b) It is based on ions and its charge
c) It is based on charges only
d) It is based on ions only
Answer: a
Clarification: The principle involved in paper chromatography is partition chromatography where the substances are partitioned between liquid phases. One phase is the mobile phase water which moves over the paper and other is the water which is held in the pores of the filter paper used.

2. What is Rf value?
a) Ratio of the distance moved by the solvent and the distance moved by the solute
b) Ratio of the distance moved by the solute and the distance moved by the solvent
c) Ratio of the concentration of solute and the concentration of the solvent
d) It Ratio of the concentration of solvent and the concentration of the solute
Answer: b
Clarification: The Rf value is defined as the ratio of the distance moved by the solute and the distance moved by the solvent along the paper, where both distances are measured from the common application Baseline.

3. What is the best solvent for paper chromatography?
a) Water
b) Alcohol
c) Vinegar
d) Methanol
Answer: a
Clarification: Paper chromatography is an inexpensive method for analyzing some types of chemical mixtures. Water is polar in nature and is commonly used as solvent in paper chromatography.

4. What does a high RF value mean in paper chromatography?
a) Substance is very non-polar
b) Substance is medium non-polar
c) Substance is polar
d) Substance is neutral
Answer: b
Clarification: A high Rf would refer to a substance that is very non-polar where substance moved. A low Rf value would refer to a substance that is very polar.

5. What are the two main types of chromatography?
a) Liquid chromatography and paper chromatography
b) Liquid chromatography and gas chromatography
c) Liquid chromatography and solid chromatography
d) Solid chromatography and gas chromatography
Answer: b
Clarification: Chromatography utilizes phase equilibrium partitioning principles to isolate proteins, nucleic acids in complex blends and has stationary phase and a mobile phase. There are two main types of chromatography: Liquid chromatography and gas chromatography.

6. Why acetonitrile is used as solvent in HPLC?
a) Improve chromatographic peak shape
b) Provide a source of protons in reverse phase LC/MS
c) Provide a source of electrons in reverse phase LC/MS
d) Improve chromatographic peak shape and provide a source of protons in reverse phase LC/MS
Answer: d
Clarification: In High pressure liquid chromatography, the B solvent used is HPLC grade organic solvent like acetonitrile, methanol with 0.1% acid. This acid is used for improving the shape of chromatographic peak and to provide source of protons in the reverse phase LC/MS.

7. Are these statements about the TFA (trifluoroacetic acid) in HPLC true?
Statement 1: It is commonly used as mobile phase additive.
Statement 2: It reduces the LC/MS signal.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: TFA (trifluoroacetic acid) is a commonly used as mobile phase additive used in reversed phase HPLC separations of proteins and peptides. TFA restrictsconsiderablyto reduces the LC/MS signal, thus lowering the sensitivity.

8. What causes peak tailing?
a) Depends on the concentration of solvent
b) Occurrence of more than one mechanism of analytic retention
c) Depends on the concentration of solute
d) No occurrence of more than one mechanism of analytic retention
Answer: b
Clarification: The primary cause of peak tailing is the existence of more than one mechanism of analytic retention. This is also due to analytic interactions with ionized silanols on the silica surface, which give rise to peak tailing. Therefore these interactions are to be minimized to achieve acceptable peak shapes.

9. Are these statements about the silica gel are used in TLC true?
Statement 1: It is widely used adsorbent and remains the dominant stationary phase.
Statement 2: The silanols are less acidic.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: Silica gel is widely used adsorbent and remains the dominant stationary phase for TLC. The surface of silica gel has highest concentration of geminal and associated silanols is favored for the TLCas these silanols are less acidic.

10. Can negative peaks occur in HPLC?
a) True
b) False
Answer: a
Clarification: A negative peak means that there is less absorbance while the peak is passing through the detector than when the mobile phase is passing through. It is due to the mobile phase which has more absorbance than the analyte at the monitored wavelength.

250+ TOP MCQs on Heat Transfer Applications – Pasteurization and Answers

Food Processing Unit Operations Multiple Choice Questions on “Heat Transfer Applications – Pasteurization ”.

1. The pasteurization process was named after ______________
a) Louis Pasteur
b) Charles Chamberland
c) Nicolas Appert
d) Clarence Birdseye
Answer: a
Clarification: The pasteurization process was developed by Louis Pasteur. Charles Chamberland developed the first pressure steam sterilizer. Nicolas Appert is the father of food technology. Clarence Birdseye developed processes for freezing fish based on quick freezing.

2. Are these statements about the pasteurization true?
Statement 1: Calcium absorption is changed with pasteurization.
Statement 2: Niacin is totally lost during pasteurization.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: d
Clarification: The calcium absorption is not changed during the pasteurization process. Similarly, niacin , riboflavin, vitamin A and vitamin D are not affected by the this process. There is a minimal loss of thiamine and vitamin B12.

3. Which of the following is called as cold pasteurization?
a) Freeze drying
b) Heating under low pressure
c) Irradiation
d) Heating at low temperature
Answer: c
Clarification: The irradiation is also known as cold pasteurization as it destroys the foodborne disease caused by pathogenic microorganisms and parasites. Unlike pasteurization, this method does not use any heat in the process instead uses the high energy rays to kill the microbes.

4. Pasteurization processes are fully effective in destroying __________
a) campylobacter
b) thermus
c) bacillus
d) thermoplasma
Answer: a
Clarification: Pasteurization processes are fully effective in destroying campylobacter. Other bacteria like thermos, bacillus and thermoplasmaare thermophiles which can grow at high temperature and cannot be destroyed by pasteurization process.

5. A pasteurization process operates to ________reductions of the target organism.
a) 12 log
b) 9 log
c) 6 log
d) 3 log
Answer: d
Clarification: A pasteurization process usually operates to 6 log reductions of the target organism. The sterilized foods have to achieve at least 12 log reductions in case of Clostridium botulinum spores. The pasteurization has lower log reductions because of the reduced risks linked with the target microbial species when associated with the botulinum toxin.

6. Are these statements about the pasteurization true?
Statement 1: Pasteurization kills the spores of bacteria.
Statement 2: Raw milk may contain pathogens.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: c
Clarification: Pasteurization kills the pathogens and reduces the number of spoilage causing microbes while maintaining food quality. Raw milk is hazardous because it can contain pathogens like E. coli,tuberculosis bacillus, salmonella, listeria and campylobacter.

7. Vat Pasteurization is also known as ___________
a) batch pasteurization
b) HTST pasteurization
c) UHT pasteurization
d) coldpasteurization
Answer: a
Clarification: Vat Pasteurization is also known as the holding method or batch pasteurization. Every particle of milk or cream is heated in equipment at 145°F (63°C) and hold for 30 minutes. Agitation is needed to achieve the appropriate consistency and texture and uniform heating or else it causes churning.

8. One pasteurization unit is the microorganism death that occurs in a product held at _______for 1 minute for beer.
a) 60°C
b) 70°C
c) 80°C
d) 50°C
Answer: a
Clarification: One pasteurization unit (PU) is the microorganism death that occurs in a product held at 60°C (140°F) for 1 minute for beer. The number of PU’s essential for a specific beverage depends on numerous factors like type of microbepresent, processing steps and type of packaging.

9. What is the pasteurization temperature of egg?
a) 140F for 2 minutes
b) 145F for 2 minutes
c) 145F for 3 minutes
d) 140F for 3 minutes
Answer: d
Clarification: Eggs are pasteurized to destroy Salmonella enteritidi at 140F for 3 minutes. This process had no adverse effect on the protein stability, foam stability and foam volume of albumen during storage.

10. Both pasteurization and sterilization destroys the spores of the bacteria.
a) True
b) False
Answer: b
Clarification: Pasteurization is not similar to sterilization. Pasteurization reduces the bacterial population of a liquid and destroys the organisms that may cause spoilage and human disease. Spores are not affected by the pasteurization process. But the sterilization process destroys the spores of the bacteria by inactivating them.

250+ TOP MCQs on Dimensions and Units and Answers

Food Processing Unit Operations Multiple Choice Questions on “ Dimensions and Units”.

1. The SI unit of film heat transfer coefficient is __________
a) W K/m2
b) Wm2K
c) (m2K)/W
d) W/ (m2K)
Answer: a
Clarification: The SI unit of film heat transfer coefficient isW K/m2. The heat transfer through convection between a solid and a fluid is measured using heat transfer coefficient. It depends on 1) Hydrodynamic characteristics of its flow, 2)Hydrodynamic characteristics of its flow and 3) Hydrodynamic and thermal boundary conditions.

2. Unit of specific gravity is _________
a) g/cm
b) g/cm3
c) kg/m3
d) dimensionless
Answer: d
Clarification: The Specific Gravity of liquids and solids is defined as dimensionless unit. It is the ratio of density of a material to the density of water at a given temperature.

3. The SI unit of dynamic viscosity is _____________
a) pascal-second
b) pascal- minute
c) poise-second
d) poise
Answer: a
Clarification: The SI unit of dynamic viscosity is the pascal-second or kilogram per meter per second. The CGS unit of dynamic viscosity is known as poise (P) which is named after Jean Leonard Marie Poiseuille.

4. Are these statements about the dimensionless quantities true?
Statement 1: A quantity which does not have any physical units.
Statement 2: Relative density and Reynolds number are examples of the dimensionless quantities.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: A quantity which does not have any physical units is called as dimensionless quantities. The relative density is the dimensionless quantity which is defined as the ratio of the density of a component to density of the given reference component. The Reynold number (R) is also a dimensionless quantity that is used to determine whether the fluid is following laminar flow (R4000).

5. What is the dimension of surface tension?
a) MLT-2
b) LT-2
c) MT-2
d) Dimensionless
Answer: c
Clarification: The surface tension is defined as the force per unit length. The dimensional formula of force is MLT-2 and for length, it is L. Therefore, the dimension of surface tension is MT-2.

6. Which of the following statements about SI units are correct?
Statement 1: There are 8 base units in SI system.
Statement 2: Gram and centimeter comes under the SI units.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: d
Clarification: There are 7 base units in SI system. They are: kilogram (kg) for mass, kelvin (K) for temperature, mole (mol) for the amount of a substance, ampere (A) for electric current, candela (cd) for luminous intensity, second (s) for time and meter (m) for distance.

7. What is the full form of SI unit?
a) International System of units
b) Indian Standards of unit
c) Standard International unit
d) International standard of units
Answer: a
Clarification: The International System of Units is the contemporary form of the metric systems and is the most commonly used system of the measurement.

8. What is the Full form of CGS unit?
a) Centimeter–gram–second
b) Centralized grand system
c) Centimeter gram system
d) Centimeter grand system
Answer: a
Clarification: Centimeter–gram–second system of units is a type of the metric system which is based on centimeter as unit of length, gram as unit of mass and second as unit of time. This is not commonly used metric type nowadays. SI units are used widely than CGS units.

9. What are the base quantities ofDimensional formula?
a) Massand length only
b) Mass and second only
c) Length and second only
d) Mass, length and second
Answer: d
Clarification: The base quantities of Dimensional formula are mass [M], length [L], Second [S]. The dimensional formula is based on the relationships between physical quantities involved, which is expressed in terms of three fundamental quantities known as mass, length and second.

10. Is Nusselt numberconsidered as a dimensionless quantity?
a) True
b) False
Answer: a
Clarification: Nusselt number is considered as dimensionless quantity which is used in calculation of the heat transfer between a moving fluid and a solid body. It is defined as the ratio of convective to conductive heat transfer across a boundary.