This set of Dairy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Changes In Milk and its Constituents”.
1. Which of the following does not accelerate rate of oxidation of fat?
a) Presence of iron and copper salts
b) Presence of dissolved oxygen
c) Exposure to light
d) Presence of water
Explanation: The presence of iron and copper salts accelerates the onset of auto-oxidation and development of metallic flavor, as does the presence of dissolved oxygen and exposure to light, especially direct sunlight or light from fluorescent tubes.
2. _______ is the principal contributor to sunlight flavor.
Explanation: Methional or 3-mercapto-methylpropionaldehyde is the principal contributor to sunlight flavor, as this particular flavor is called. It is a typical off-flavor found in milk.
3. What is the process of breakdown of fat into glycerol and free fatty acid called?
Explanation: The breakdown of fat into glycerol and free fatty acids is called lipolysis. Lipolysed fat has a rancid taste and smell, caused by the presence of low molecular free fatty acids.
4. Enzyme responsible for Lipolysis is :
Explanation: Lipolysis is caused by the action of lipases. Lipolysis is encouraged by high storage temperatures.
5. The purpose of heat treatment on milk is:
a) Kill pathogenic microorganism
b) Heat milk
d) Taste enhancement
Explanation: Heat treatment on milk aims to kill pathogenic microorganism. Heat treatment of milk also enhances its shelf life.
6. The fat globules in milk when heated to 74℃ show which of the following phenomenon?
c) Cream plug formation
Explanation: It has been shown that when milk is pasteurized at 70 – 80°C for 15 seconds, the cream plug phenomenon is already evident at 74°C.
7. ________ is recommended in order to avoid cream plug formation.
Explanation: Homogenization is practiced to avoid cream plug formation. Cream plug formation leads to blockage in pipes and tubes.
8. What is the result of heat treatment on proteins?
c) Spore formation
d) Froth formation
Explanation: Proteins on heat treatment undergo denaturation. Denaturing of protein leads to off flavor.
9. Denature Protein contribute to improvement of quality of which of the following products?
a) Cultured milk product
c) Ice cream
Explanation: In milk intended for cultured milk products (yoghurt, etc.), the whey protein denaturation and interaction with casein obtained at 90 – 95°C for 3 – 5 minutes will contribute to improved quality in the form of reduced syneresis and improved viscosity.
10. Effect of Heat treatment (Temperature above 100℃) on Lactose:
a) Greenish color
b) Bluish color
c) Brownish color
d) Reddish color
Explanation: Lactose undergoes changes more readily in milk than in the dry state. At temperatures above 100 °C a reaction takes place between lactose and protein, resulting in a brownish color.
11. The lactulose content ______ with increased intensity of the heat treatment.
c) Remains same
d) First increase and then decrease
Explanation: The lactulose content thus increases with increased intensity of the heat treatment. It may lead to denaturation of proteins.
12. Most Heat sensitive vitamin in milk is?
a) Vitamin A
b) Vitamin B
c) Vitamin C
d) Vitamin D
Explanation: Vitamin C is most heat sensitive vitamin in milk among all other. Milk is a rich source of Vitamin A& D.
13. Effect of Pasteurization on Vitamins in Milk :
a) Great loss
b) Little or no loss
Explanation: Pasteurization in a plate heat exchanger can however, be accomplished with virtually no loss of vitamin C. The other vitamins in milk suffer little or no harm from moderate heating.
14. Which of the following mineral is affected by heat treatment in milk?
Explanation: Of the minerals in milk only the important calcium hydroxyphosphate in the casein micelles is affected by heating. Rest has no affect on heating.
15. Heat treatment on minerals results leads to :
a) Clumps formation
b) Bubble formation
c) Foul smell
d) Loss of cheese making characteristics
Explanation: When heated above 75°C the substance loses water. Loss of water leads to formation of insoluble calcium orthophosphate; which impairs the cheese making properties of the milk.
Sanfoundry Global Education & Learning Series – Dairy Engineering.
To practice all areas of Dairy Engineering, here is complete set of 1000+ Multiple Choice Questions and Answers.