# Dairy Engineering Questions and Answers – Physical Properties of Milk

This set of Dairy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Physical Properties of Milk”.

1. Opacity in milk is due to which of the following reasons?
a) White color
b) Heat treatment
d) Suspended particles of fat

Explanation: The opacity of milk is due to its content of suspended particles of fat, proteins and certain minerals. Heat treatment has no effect on opacity.

2. Yellowish tinge in milk can be attributed to which of the following?
a) Carotene
b) Water
c) Riboflavin
d) Metalin

Explanation: The color varies from white to yellow according to the coloration (carotene content) of the fat. This is also the main reason behind the yellow color of the butter.

3. In an equation Fat%, SNF% and water determine‘d’. The‘d’ in this expression is?
a) Viscosity
b) Friction force
c) Density
d) Acceleration

Explanation: The d is the density of milk at the temperature 15.5℃.Density is basically the degree of compactness of the substance.

4. Calculate the density of milk at 15.5℃ having 3.2% fat and 8.5% SNF.
a) 2.03 g/cm3
b) 1.03 g/cm3
c) 4.03 g/cm3
d) 5.03 g/cm3

Explanation: Density of milk at 15.5℃ having 3.2% fat and 8.5% SNF is 1.03 g/cm3. It can be calculated using the formula.

5. Milk is ______ with blood.
a) Hypertonic
b) Hypotonic
c) Isotonic
d) No pressure

Explanation: Milk is isotonic with blood. Isotonic denoting or relating to a solution having the same osmotic pressure as some other solution, especially one in a cell or a body fluid.
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6. Osmotic pressure is controlled by the number of molecules or particles, not the weight of solute.
a) True
b) False

Explanation: Osmotic pressure is controlled by the number of molecules or particles, not the weight of solute; thus 100 molecules of size 10 will have 10 times the osmotic pressure of 10 molecules of size 100.

7. Define the temperature at which a liquid turns into a solid when cooled.
a) Boiling point
b) Melting point
c) Freezing point
d) Evaporation temperature

Explanation: The temperature at which a liquid turns into a solid when cooled is called freezing point. The Freezing point of milk is closer to 0℃.

8. Freezing point helps to check which of the following adulteration in milk?

Explanation: The freezing point of milk is the only reliable parameter to check for adulteration with water. The freezing point of milk from individual cows has been found to vary from –0.54 to –0.59°C.

9. The acidity of a solution is dependent on which of the following?
a) Water content
b) Fat content
c) Acid content
d) [H+] ions

Explanation: The acidity of a solution depends on the concentration of hydronium ions [H+] in it. When the concentrations of [H+] and [OH–] (hydroxyl) ions are equal, the solution is called neutral.

10. What does pH of the solution represent?
a) Solubility
b) Osmotic pressure
c) Hydronium ion concentration
d) Water content

Explanation: The pH represents the hydronium ion concentration of a solution and can mathematically be defined as the negative logarithm of the hydronium ion [H+] concentration.

11. pH of normal milk is _____ at 25℃.
a) 4
b) 4.3
c) 6.6
d) 9

Explanation: Normal milk is a slightly acid solution with a pH falling between 6.5 and 6.7 with 6.6 the most usual value. The temperature of measurement near 25°C.

12. In determining acidity, the solution in the burette is?
a) Hydrochloric acid
b) Potassium salt
c) Potash alum
d) Sodium Hydroxide solution

Explanation: The blue liquid present in the burette in this picture is a NaOH solution. NaoH is a basic solution.

13. Titratable acidity of milk cannot be expressed in which of the following degree?
a) ᵒSH
b) ᵒTh
c) ᵒD
d) ℃

Explanation: °SH = Soxhlet Henkel degrees, °Th = Thörner degrees; °D = Dornic degrees, all three can be used to express titratable acidity.

14. 1.7 ml of N/10 NaOH is required for titration of a 10 ml sample of milk. Compute the titratable acidity.
a) .17 °Th
b) 170 °Th
c) 17 °Th
d) 10 °Th

Explanation: 10 x 1.7 = 17 ml would therefore be needed for 100 ml, and the acidity of the milk is consequently 17 °Th.

15. The first milk that a cow produces after calving is called ________
a) Cream
b) Butter
c) Colostrum
d) High fat milk

Explanation: The first milk that a cow produces after calving is called Colostrum. Colostrum has brownish-yellow color, peculiar smell and a rather salty taste. The content of catalyzes and peroxidase is high.

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