This set of Dairy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Homogenizer – 1”.
1. Name the scientist who invented Homogenization?
a) Pasteur
b) Rutherford
c) Leuwenhoek
d) Gaulin
View Answer
Explanation: Gaulin, who invented the process of homogenization in 1899, described it in French as “fixer la composition des liquids”.
2. Disruption of fat globules into much smaller fat globules is defined as?
a) Standardization
b) Centrifugation
c) Homogenization
d) Chilling
View Answer
Explanation: Homogenization has become a standard industrial process, universally practiced as a means of stabilizing the fat emulsion against gravity separation. Homogenization primarily causes disruption of fat globules into much smaller ones.
3. Disintegration of fat globules in homogenization is achieved by which of the following?
a) Turbulence
b) Cavitation
c) Turbulence and cavitations
d) Pasteurization
View Answer
Explanation: The disintegration of the original fat globules is achieved by a combination of contributing factors such as turbulence and cavitations. The net result reduces the fat globules to approximately 1mm in diameter.
4. Cream with higher fat content than ____ cannot normally be homogenized at the normal high pressure.
a) 5%
b) 10%
c) 12%
d) 15%
View Answer
Explanation: Cream with higher fat content than 12 % cannot normally be homogenized at the normal high pressure because clusters are formed as a result of lack of membrane material (casein). A sufficiently good homogenization effect requires approximately 0.2 g casein per g of fat.
5. Homogenization of cold milk is ineffective.
a) True
b) False
View Answer
Explanation: Homogenization of cold milk, in which the fat is essentially solidified, is virtually ineffective. Processing at temperatures conducive to the partial solidification of milk fat (i.e. 30 – 35°C) results in incomplete dispersion of the fat phase.
6. Homogenization temperature applied normally are ________
a) 30- 40℃
b) 50- 60℃
c) 60- 70℃
d) 90-100℃
View Answer
Explanation: Homogenization temperatures normally applied are 60 – 70°C, depending on the product. Processing at temperatures conducive to the partial solidification of milk fat (i.e. 30 – 35°C) results in incomplete dispersion of the fat phase. Homogenization is most efficient when the fat phase is in a liquid state and in concentrations normal to milk.
7. Preferred Homogenization pressure is _______
a) 5- 15 MPa
b) 10-25 MPa
c) 25- 50 MPa
d) 60-70 MPa
View Answer
Explanation: Homogenization pressure is between 10 and 25 MPa (100 – 250 bar), depending on the product. High-pressure homogenisation procedures cause the formation of small fat globules.
8. The dispersion of the lipid phase increases with ________ temperatures of homogenisation and is commensurate with the_________ viscosity of milk at higher temperatures.
a) Increase, decrease
b) Increase, increase
c) Decrease, increase
d) Decrease, decrease
View Answer
Explanation: The dispersion of the lipid phase increases with increasing temperatures of homogenization and is commensurate with the decreasing viscosity of milk at higher temperatures.
9. Name the theory of homogenization According to which homogenization takes place when the liquid is leaving the gap, so the back pressure which is important to cavitation is important to homogenization.
a) Cavitation theory
b) Eddies theory
c) Current theory
d) Voltage theory
View Answer
Explanation: The cavitation theory, on the other hand, claims that the shock waves created when the steam bubbles implode disrupt the fat droplets. However, it is possible to homogenise without cavitation, but it is less efficient.
10. Which homogenization theory predicts how the homogenisinneffect varies with the homogenizing pressure?
a) Cavitation theory
b) Eddies theory
c) Current theory
d) Voltage theory
View Answer
Explanation: The theory of globule disruption by turbulent eddies is based on the fact that a lot of small eddies are created in a liquid travelling at a high velocity. Higher velocity gives smaller eddies. If an eddy hits an oil droplet of its own size, the droplet will break up. This theory predicts how the homogenizing effect varies with the homogenizing pressure.
11. Application of Single-stage homogenization is in?
a) Products demanding a high viscosity (certain cluster formation).
b) Product with low viscosity
c) Product with no viscosity
d) Product without fat
View Answer
Explanation: Single-stage homogenization may be used for homogenization of products demanding a high viscosity (certain cluster formation).
12. Two-stage homogenization may not be applied to which of the following?
a) Products with a high fat content
b) Products where high homogenization efficiency is desired.
c) Product with low viscosity
d) Product demanding high viscosity
View Answer
Explanation: Two-stage homogenization is used for products with a high fat content and products where high homogenization efficiency is desired.
13. Two-stage method is usually chosen to achieve optimal homogenization efficiency.
a) True
b) False
View Answer
Explanation: pressure is measured before the first stage, P1, and the homogenization pressure in the second stage is measured before the second stage, P2. The two-stage method is usually chosen to achieve optimal homogenization efficiency. Best results are obtained when the relation P1 / P2 is about 0.2.
14. The effect of homogenization on the physical structure of milk has which of the following advantages?
I) Smaller fat globules leading to no cream-line formation
II) Somewhat increased sensitivity to light – sunlight and fluorescent tubes
III) Reduced heat stability
a) I) only
b) I) and III)
c) I), II) and III)
d) II) only
View Answer
Explanation: Homogenization has following advantages: Smaller fat globules leading to no cream-line formation, Whiter and more appetizing color, reduced sensitivity to fat oxidation, more full-bodied flavor, better mouth feel, and Better stability of cultured milk products.
15. Homogenization of milk may give milk which of the following off-flavor?
a) Fruity
b) Bitter
c) Sunlight
d) Salty
View Answer
Explanation: Homogenization has a disadvantage of increased sensitivity to light – sunlight and fluorescent tubes can result in Sunlight flavor to the milk.
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