Engineering Questions with Answers - Multiple Choice Questions
Primary Production of Milk Engineering MCQs
1 - Question
Pasteurization aid in which of the following?
a) killing tubercle bacillus
b) killing spores
c) increasing fat content
d) lowering temperature
View Answer
Explanation: The pasteurization of milk is a special type of heat treatment which can be defined as “any heat treatment of milk which secures the certain destruction of tubercle bacillus (T.B.) without markedly affecting the physical and chemical properties”.
2 - Question
Which of the following is the time-temperature combination for HTST pasteurization?
a) 72°C to 74°C for 15 to 20 seconds
b) 135°C to 140°C for 2 to 4 seconds
c) 63°C for 30 minutes
d) 57°C to 68°C for 15 min
View Answer
Explanation: High temperature short time (HTST) pasteurization. Heat the milk to between 72°C to 74°C for 15 to 20 seconds. Targets resistant pathogenic bacterial spores (Clostridium botulinum spores).
3 - Question
Which of the following is the time-temperature combination for LTST pasteurization?
a) 72°C to 74°C for 15 to 20 seconds
b) 135°C to 140°C for 2 to 4 seconds
c) 63°C for 30 minutes
d) 57°C to 68°C for 15 min
View Answer
Explanation: Low temperature long time (LTLT) pasteurization involves heating the milk to 63°C for 30 minutes. The extended holding time causes alteration in the milk protein structure and taste.
4 - Question
Which of the following is the time-temperature combination for UHT pasteurization?
a) 72°C to 74°C for 15 to 20 seconds
b) 135°C to 140°C for 2 to 4 seconds
c) 63°C for 30 minutes
d) 57°C to 68°C for 15 min
View Answer
Explanation: UHT Pasteurization involves heating the milk to between 135°C to 140°C for 2 to 4 seconds. The extreme heat targets Coxiella burnetii, which causes Q-fever. The heat kills all the vegetative forms of bacteria and the milk can survive for 9 months.
5 - Question
Which of the following is the time-temperature combination for Thermization?
a) 72°C to 74°C for 15 to 20 seconds
b) 135°C to 140°C for 2 to 4 seconds
c) 63°C for 30 minutes
d) 57°C to 68°C for 15 min
View Answer
Explanation: Thermization involves heating the milk to between 57°C to 68°C and hold for 15 minutes. Thermization targets pathogenic bacteria while leaving the good bacteria in the product. The low temperatures do not alter the structure and taste of the milk.
6 - Question
Which of the following is the time-temperature combination for Sterilization?
a) 72°C to 74°C for 15 to 20 seconds
b) 135°C to 140°C for 2 to 4 seconds
c) 63°C for 30 minutes
d) 115 – 120°C for some 20 – 30 minutes
View Answer
Explanation: Sterilization is a wet treatment of canned milk products in an autoclave/specialized treatment chambers. Heat to between 115°C to 121°C for 10 to 20 minutes.
7 - Question
“Heat transferred from the bowl of the spoon to the handle” is an example of which of the following way of heat transfer?
a) Conduction
b) Convection
c) Radiation
d) Filtration
View Answer
Explanation: Conduction means a transfer of thermal energy through solid bodies and through layers of liquid at rest (without physical flow or mixing in the direction of heat transfer). The question shows an example of heat conduction to a teaspoon in a cup of hot coffee. Heat is transferred by conduction to the handle, which becomes warmer.
8 - Question
“The spoon is rinsed in running cold water. Heat gets absorbed by the water and the spoon gets cooler, until the spoon and the water are at the same temperature” is an example of which of the following way of heat transfer?
a) Conduction
b) Convection
c) Radiation
d) Filtration
View Answer
Explanation: Convection consequently involves mixing. When the teaspoon is rinsed with running cold water, heat gets transferred from the spoon to the water, which is heated in the process. The heated water when replaced by cold water, which in turn absorbs heat from the spoon. Heat transfer by convection continues until the spoon and the running water have the same temperature.
9 - Question
“A roof accumulates solar heat during the day and radiates the heat at night” is an example of which of the following way of heat transfer?
a) Conduction
b) Convection
c) Radiation
d) Filtration
View Answer
Explanation: Radiation is the emission of heat from a body which has accumulated thermal energy. In the given example the thermal energy is converted into radiant energy, emitted from the body and absorbed by other bodies which it strikes. Almost all substances emit radiant energy.
10 - Question
Which of the following is the application of direct heating in the dairy industry?
a) Heating curd in the manufacture of cheese
b) Solar heating
c) Heating with gamma rays
d) Oxidation
View Answer
Explanation: Direct heating means that the heating medium is mixed with the product. This technique is used in heating the curd in the manufacture of cheese in dairy industry.
11 - Question
Heat exchanger works on which of the following principle?
a) Direct heating
b) Indirect heating
c) Slow heating
d) Fast heating
View Answer
Explanation: A heat exchanger is used to transfer heat by the indirect method. Hot water flows through one channel and milk through the other. Heat is transferred through the partition.
12 - Question
If the product flow rate in a plant is to be increased from 10 000 l/h to 20 000 l/h, the heat exchanger must be extended to_______ the original size, provided the flow rates of the service media are also doubled, other factors being constant.
a) Double
b) Triple
c) Same
d) Quadruple
View Answer
Explanation: In the question the size needs to be doubled as The flow rate, V, is determined by the planned capacity of the dairy. The higher the flow rate, the larger the heat exchanger needed.
13 - Question
Calculate temperature change: 20 000 l/h cheese milk (V1) is to be heated from 4°C to 34°C by 30 000 l/h hot water (V2) at 50°C. Density (r) and specific heat (cp) for milk are about 1020 kg/m3 and 3.95 kJ/kg, K and for water 990 (at 50°C) and 4.18.
a) 20.5℃
b) 21.5℃
c) 18.8℃
d) 19.5℃
View Answer
Explanation: The temperature change for the hot water can then be calculated: 20 000 x 1 020 x 3.95 x (34 – 4) = 30 000 x 990 x 4.18 x Dt2 Dt2 = 19.5°C. The hot water temperature will drop by 19.5 from 50 to 30.5°C.
14 - Question
The temperature difference between the two liquids is best utilized if they flow in opposite directions through the heat exchanger. This type of flow is called ________
a) Countercurrent
b) Concurrent
c) Rapid flow
d) Slow flow
View Answer
Explanation: The cold product then meets the cold heating medium at the inlet and a progressively warmer medium as it passes through the heat exchanger. During the passage, the product is gradually heated so that the temperature is always only a few degrees below that of the heating medium at the corresponding point. This type of arrangement is called a countercurrent flow.
15 - Question
______________ tells how much heat passes through 1 m2 of the partition per 1°C of differential temperature.
a) Friction coefficient
b) Temperature coefficient
c) Overall heat transfer coefficient
d) Time coefficient
View Answer
Explanation: The overall heat transfer coefficient refers to how well heat is conducted over a series of mediums. This factor, k, is a measure of how efficient the heat transfer is.
16 - Question
Which among the following surface promote heat transfer?
a) Plain
b) Shiny
c) Corrugated
d) Wet
View Answer
Explanation: The partition is often corrugated to create a more turbulent flow, which results in better heat transfer. The thickness is also important. The thinner the partition, the better the heat transfers.
17 - Question
_______ Heat exchanger is needed for cream than for milk, if capacities and temperature programs are identical.
a) Larger
b) Smaller
c) Similar
d) Stagnant
View Answer
Explanation: A liquid with high viscosity develops less turbulence when it flows through the heat exchanger compared to a product with lower viscosity. This means a larger heat exchanger is needed, everything else being constant.
18 - Question
Which of the following material is used for heat transfer in the dairy industry?
a) Iron
b) Platinum
c) Copper
d) Stainless steel
View Answer
Explanation: For food processing, the normal material is stainless steel. It has fairly good heat transfer characteristics.
19 - Question
The rate of buildup of fouling does not depend on which of the following?
a) Milk quality and Air content of the product
b) Temperature difference between product and heating medium
c) Pressure conditions in the heating section
d) Thickness of stainless steel
View Answer
Explanation: The rate of buildup of fouling depends on many factors such as temperature difference between product and heating medium, Milk quality, Air content of the product and Pressure conditions in the heating section.
20 - Question
What is the method of using the heat of a hot liquid, such as pasteurized milk, to preheat cold incoming milk?
a) Heating
b) Cooling
c) Regeneration
d) Standardization
View Answer
Explanation: Regeneration (Heating): The raw cold incoming milk is partially and indirectly heated by the hot outgoing milk (milk-to-milk regeneration). This adds to the economy.
21 - Question
Zigzag tube in heat treatment is used for which purpose?
a) Fouling
b) Standardization
c) Holding for a long holding time
d) Discard
View Answer
Explanation: Correct heat treatment requires that the milk is held for a specified time at pasteurization temperature. This is done in an external holding cell. A holding cell usually consists of a pipe arranged in a spiral or zigzag pattern and often covered by a metal shroud to prevent people from being burned if they touch the holding cell.
22 - Question
Which heat exchanger used for heating and cooling viscous, sticky and lumpy products?
a) Plate heat exchanger
b) Tubular heat exchanger
c) Scraped surface heat exchanger
d) Spray dryer
View Answer
Explanation: The scraped-surface heat exchange is designed for heating and cooling viscous, sticky and lumpy products and for crystallization of products. The operating pressures on the product side are high, often as much as 40 bar. All products that can be pumped can therefore be treated.
23 - Question
PHE (Plate Heat Exchanger) is more efficient in terms of heat transfer than THE (Tubular Heat Exchanger).
a) True
b) False
View Answer
Explanation: The given statement is true. From the standpoint of heat transfer, the tubular heat exchanger is less efficient than a plate heat exchanger.
24 - Question
Which of the following is/are the category of Tubular Heat exchanger?
a) Multi/mono channel
b) Multi/mono tube
c) Cubical channel
d) Multi/mono channel and Multi/mono tube
View Answer
Explanation: Tubular heat exchangers (THE) are in some cases used for pasteurization/ UHT treatment of dairy products. Tubular heat exchangers are available in two fundamentally different types; multi/mono channel and multi/mono tube.
25 - Question
Heat exchanger characterized by pack of stainless steel in a frame is ________
a) Plate heat exchanger
b) Tubular heat exchanger
c) Scraped surface heat exchanger
d) Spray dryer
View Answer
Explanation: Most heat treatment of dairy products is carried out in plate heat exchangers. The plate heat exchanger (often abbreviated PHE) consists of a pack of stainless steel plates clamped in a frame.
26 - Question
Scraped Heat exchanger has a ______ design.
a) Simple
b) Vertical
c) Planar
d) Horizontal
View Answer
Explanation: Thanks to the vertical design, the product can be displaced by water with minimum intermixing which helps assure product recovery at the end of every run. Following this, completely drainage facilitates CIP and product changeover.
27 - Question
Plate heat exchanger was patented in which year?
a) 1890
b) 1990
c) 2009
d) 1790
View Answer
Explanation: The plate heat exchanger was patented in 1890 by the German inventors Langen and Hundhausen.
28 - Question
“R” in the below equation refers to what?
<br/>
a) Recycle<br/>
b) Regeneration efficiency<br/>
c) Regression<br/>
d) Reuse<br/>
View Answer
Explanation: We can take the simplest operating profile – heat treatment of raw milk –as an example. Using this formula: where R = regenerative efficiency %, tr = milk temperature after regeneration, ti = temperature of raw incoming milk, tp = pasteurization and temperature.
29 - Question
The unwanted buildup of material on a surface is called?
a) Secretion
b) Plating
c) Fouling
d) Layering
View Answer
Explanation: Fouling is the accumulation of unwanted material on solid surfaces to the detriment of function. Dairy industry also experiences fouling problems by chemical reactions.
30 - Question
Heat must be supplied to a substance in order to increase its temperature by 1°C is called?
a) Plate heat
b) Specific heat
c) Heat of chemical reaction
d) Heat of crystallization
View Answer
Explanation: Specific heat, cp, is also determined by the product. The specific heat is basically the amount of heat per unit mass required to raise the temperature by one degree Celsius.