Food Engineering
Compiled By: - Mr. Girish Rajpurohit
Q. What is an ideal solid?
A.An ideal solid material deforms
instantaneously when a load is applied. It returns to its original
configuration instantaneously (complete recovery) upon removal of the load.
Q. What is hooke's law that is
followed by ideal elastic material?
A. It states that the the stress
(τ ) is directly proportional to the strain (γ ). The proportionality constant
(G) is called the modulus.
Q. What is an ideal fluid?
A.
An ideal fluid deforms at a constant rate under an applied stress, and the
material does not regain its original configuration when the load is removed.
Q. What is Newton’s law which
describe flow of simple viscous material?
A.The flow of a simple viscous
material is described by Newton’s law, where the shear stress (τ ) is directly
proportional the shear rate. The proportionality constant (η) is called the
Newtonian viscosity.
Q. Moisture sorption isotherm is
plot between moisture content (DB) and _____
A.
Water Activity
Q. Which type of freezer is Plate
freezer?
A. Non-contact freezer.
Q. Which effect causes freezing
point depression (FPD)?
A. Concentration effect (more
concentration of solute more FPD)
Q. Which type of freezing is IQF?
A. Rapid freezing
Q. What is rheology?
A. Study of flow and deformation.
Q. What is strain?
A. The unit change, due to force, in
the size or shape of a body with respect to it’s original size and shape.
Q. What is stress?
A. It is force per unit area where
action of force is perpendicular to the surface.
Q. What is shear stress?
A. It is force per unit area where
action of force is parallel or tangential
to the surface.
Q. What is shear rate?
A.Shear rate is the rate
of change of velocity at which one layer of fluid passes over an adjacent
layer. As an example, consider that a fluid is placed between two parallel
plates that are 1.0 cm apart, the upper plate moving at a velocity of 1.0
cm/sec and the lower plate fixed.
Q. What is linear
strain?
A.The change per unit
length due to force in an original linear direction.
Q. What is
coefficient of viscosity?
A. It is the ratio
between shear stress to the rate of shear (Newtonian liquids).
Q. What is
kinematic viscosity?
A. It is coefficient
of viscosity (dynamic viscosity) divided by mass density.
Q. What is modulus
of elasticity?
A.The ratio of stress
to corresponding strain below the proportional limit.
Q. What is resilience?
A. It is the property of material
to absorb energy in the form of strain energy in elastic range when it is
deformed elastically. When load is removed the energy is recovered.
Q. What is cryogenic freezing?
A. It means freezing done at very
low temperatures (-150c) using liquid N2 or such refrigerant.
Q. What is critical moisture
content?
A. Critical moisture content is the
amount of moisture content pres3nt in the food roduct at the end of constant
drying rate period.
Q. What is latent heat?
A. Heat energy given to a
substance for its phase conversion only i.e. during this process temperature
remains constant.
Q. What is sensible heat?
A. Heat required to change a
temperature of the substance (within single phase).
Q. What is the mode of heat
transfer in vacuum drying?
A. Conduction
Q. What is the use of Plank’s
equation?
A.Calculation of freezing time
(phase conversion only).
Q. What are the assumptions of
Plank’s equation?
A. a. It doesn’t take the length
aspect of food product in consideration.
b. It only consider the phase change
aspect.
Q. What do you mean by water
activity?
A.Water activity (aw) is the
partial vapour pressure of water in a substance divided by the partial vapour
pressure of pure water at the same temperature. It is also given by ERH/100.
Q. What is the value of yield
stress in shear thinning liquid?
A. Zero
Q. What do you mean by impact
loading?
A. Static rapid loading such that
forces are exerted and removed in a very short period of time.
Q. What are the unit of
convective heat transfer coefficient?
A.W/m^2.k
Q. Which type of dryer are mostly
used for grains?
A. Bin dryer.
Q. Temperature sweep test in
rheometer is plotbetween?
A.Viscosity vs Temperature
Q. Spray drier atomiser used for
high Total solids product is?
A. Disc atomiser.
Q. What is threshold strength?
A.It is the stress required to
initiate deformation.
Q. What is yield strength?
A.It the stress at which soft
materials begin to yield.
Q. What is fracture strength?
A. It is the stress at which
brittle materials fracture.
Q. What is creep?
A. Deformation with time, when the material
is suddenly subjected to a dead load (constant stress).
Q. What is viscoelasticity?
A. It is a combined solid like and
liquid like behaviour in which the stress-strain relationship is time
dependent.
Q. What is poisson's ratio?
A. It is the ratio between the
lateral contraction (as a fraction of the diameter ) and the longitudinal
elongation. It is dimensionless.
Q. What is creep behavior?
A. It is the slow and progressive
deformation with time under a constant stress.
Q. Condition for a commodity to
neither losse or gain moisture is ?
A.Pressure of atmosphere around it
equals to the pressure of the commodity.
Q. What is a good advantage of
fluidized bed drier?
A. Entire material is continuously
exposed to heat source.
Q. What is the other name of
freeze drier?
A.Lyophilizer.
Q. Water activity of pure water
in a cup us?
A. One
Q. Initial drying period is
followed by a much slower rate of drying as the moisture content of the food
______ ?
A. Decreases
Q. Water activity of bound water
is ?
A. Less than one.
Q. Convert 22% moisture content
on wet basis to dry basis?
A. 22/88 *100 = 28.2%.
Q. What is liquid diffusion?
A. The phenomenon of liquid
movement due to moisture concentration difference.
Q. Freezing curve is a plot
between?
A. Temperature and time.
Q. List the steps of freezing
process in sequence?
A.Supercooling, nucleation,
crystallization, freezing.
Q. Enzyme used to check
effectiveness of blanching?
A.Peroxidase enzyme.
Q. The working element if engleberg
dehuller is?
A.Ribbed cast iron roller.
Q. Rubber-roll sheller consists of
two rollers rotation in _____ direction at ______ speed?
A. Opposite, different.
Q. Distillation is a process
which separates components based on their ______ ?
A. Vapour pressure.
Q. Wastage of water in ______
blancher can be reduced by using _____?
A. Hot water, steam.
Q. What is enzymatic browning?
A.Enzymatic browning is a chemical
process which occurs in fruits and vegetables by the enzyme polyphenoloxidase,
which results in brown pigments.
Q. What are objectives of
blanching?
A.aTo soften the tissue to
facilitate packaging.
b. To avoid damage to the product.
c. To eliminate air form the product.
d. To preserve the natural colour.
e. To destroy or retard certain
undesirable enzymes.
f. To help preserve natural flavour.
Q. What is viscosity?
A.Viscosity is a measure of a
fluid’s resistance to flow.
Q. Examples of pseudoplastic
(shear thinning) fluids?
A. Cosmetic lotions, dahi in lassi
preparation etc.
Q. Examples of dilatant (shear
thickening) fluids?
A.Soup, hydrocolloid solution, corn
powder etc.
Q. What do you mean by Newtonian
fluids?
A.A Newtonian fluid (named for
Isaac Newton) is a fluid whose stress versus rate of strain curve is linear and
passes through the origin. The constant of proportionality is known as the
viscosity.
Q. Power law model is also
called?
A. Ostwald model.
Q. Ideal Elastic body is
represented by?
A. Spring
Q. Ideal Elastic body is
represented by?
A. A friction block.
Q. Comparison of springs and
dashpots?
A.Springs:- Purely Elastic Respond
Instantaneously Store Energy Hook’s Law.
Dashpots:- Purely Viscous Slow response
Dissipate Energy in form of heat Newton’s Law.
Q. Give classification of time
dependent fluids?
A. Thixotropic and rheopectic.
Q. Enlist various types of
distillation?
A.Simple Distillation, Fractional
Distillation, Vacuum Distillation, Steam distillation, Batch Distillation,
Continuous Distillation.
Q. What is theprinciple of
fractional distillation?
A. Separation on the basis of
different boiling points of different fluids.
Q. What is dehulling?
A. It meansremoving husk from any
grain or seeds with minimum damage to the bran layer and as far as possible not
to break the grains.
Q. What is pulping?
A.Pulping is process that performed
by the extraction or pulper equipment which crush the food products and
separate the pulp, seed and skin of fruits and
vegetable.
1.
ICAR
E-course (Food engineering)
2.
NDRI
class notes
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