This set of Food Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Liquid Dispersions”.
1. What in dispersion can cause a strong disturbance in sedimentation of particles?
a) Convection current
b) Dispersion current
c) Emulsive force
d) Sedimentation force
View Answer
Explanation: Convection current in the dispersion, caused by slight temperature fluctuations, may strongly disturb sedimentation of particles.
2. Why does an anisometric particle tends to sediment more slowly?
a) Due to convection current
b) Due to the shape of the particle
c) It orients itself to maximize friction
d) Due to dispersion current
View Answer
Explanation: Anisometric particles are not homogenous spheres. So they tend to sediment more slowly, because it orients itself during sedimentation in such a way as to maximize friction.
3. Why does an aggregate of particle, though spherical sediment more slowly than a homogenous sphere?
a) They can’t orient themselves
b) Since their density differences are smaller
c) No interstitial liquids
d) They are not spherical
View Answer
Explanation: An aggregate of particles, even if spherical sediments more slowly than a homogenous sphere of same size, since the interstitial liquid in the aggregate cause the effective density difference to be smaller.
4. By how much % does the sedimentation rate reduce if the volume fraction of particle is not very small?
a) 50%
b) 20%
c) 40%
d) 60%
View Answer
Explanation: If the volume fraction of particle is not very small, sedimentation is hindered. The sedimentation rate will be reduced by about 60%.
5. What happens when the particles aggregate?
a) Sedimentation velocity decreases
b) Sedimentation velocity increases
c) Flow rate decreases
d) Flow rate increases
View Answer
Explanation: If particles aggregate, sedimentation velocity increases. The increase in d2 is always larger than the decrease in Δp.
6. True or false: Larger aggregates sediment faster they overtake the smaller one.
a) True
b) False
View Answer
Explanation: Larger aggregates sediment faster they overtake the smaller one, and thus become ever larger, leading to an even greater acceleration of sedimentation rate. This may enhance sedimentation by orders of magnitude.
7. The fat globules in raw milk aggregate by the presence of what?
a) Lactose
b) Cryoglobulins
c) Lipoprotiens
d) Phospholipids
View Answer
Explanation: There happens a rapid creaming in cold raw milk, as the fat globules aggregate due to the presence of cryoglobulins.
8. The rate of aggregation is calculated using which theory?
a) Smoluchowski’s theory
b) Newton laws
c) Pythagorous theory
d) Theory of kinetics
View Answer
Explanation: The rate of aggregation is usually calculated according to smoluchowski’s theory of perikinetic aggregation.
9. A state in which the particles stay close together for a much longer time than they would in the absence of attractive colloidal interaction is called?
a) Sedimentation
b) Gelatinization
c) Aggregation
d) Dispersion
View Answer
Explanation: Particles in a liquid exhibit Brownian motion and thereby frequently encounter each other. Aggregation is defined as a state in which the particles stay close together for a much longer time than they would in the absence of attractive colloidal interaction.
10. Diluting in water can cause?
a) Sedimentation
b) Deaggregation
c) Aggregation
d) Dispersion
View Answer
Explanation: Diluting in water can cause deaggregation due to lowering osmotic pressure, lowering ionic strength, due to enhancing solvent quality.
Sanfoundry Global Education & Learning Series – Food Chemistry.
To practice all areas of Food Chemistry, here is complete set of Multiple Choice Questions and Answers.
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