Thermal operations - Food Engineering - Engineering Sciences Previous Year Questions

1

2008 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2008

Following operations are adopted for cleaning in place (CIP) of equipment
P: Cold water rinse; Q: Hot water rinse; R: Alkali cleaning; S: Acid cleaning
The correct sequence of CIP for equipment used in UHT processing of milk is

A

P → Q → R → S → P

B

P → Q → R → Q → S → P

C

P → Q → R → P

D

P → Q → S → P

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2

2008 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2008

Match the items in Group I with the most appropriate items in Group II

Group I	Group II
(P) Disc centrifuge	(1) Separation of solid phase in milk by coagulation
(Q) Multiple effect evaporator	(2) Aseptic packaging of milk
(R) UHT processing	(3) Separation of liquid phases in milk
(S) Homogenization	(4) Dispersion of one of the liquid phases in milk
	(5) Concentration of milk

A

P-3, Q-5, R-1, S-4

B

P-1, Q-5, R-2, S-4

C

P-3, Q-5, R-2, S-1

D

P-3, Q-5, R-2, S-4

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3

2008 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2008

A medium acid food is sterilized at 100°C in a can to reduce the number of heat resistant organism (\( D_{120} = 0.2 \) min, \( z = 10°C \)) from an initial count of 10000 per can to a probability of survival of 1 in million. \( D_{100} \) value of this organism is

A

0.4 min

B

20 min

C

4 min

D

10 min

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4

2008 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2008

A medium acid food is sterilized at 100°C in a can to reduce the number of heat resistant organism (\( D_{120} = 0.2 \) min, \( z = 10°C \)) from an initial count of 10000 per can to a probability of survival of 1 in million. The total processing time is

A

100 min

B

40 min

C

200 min

D

4 min

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5

2009 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2009

The most suitable evaporator for concentration of fruit juices is

A

agitated film evaporator

B

falling film evaporator

C

long tube evaporator

D

short tube evaporator

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6

2009 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2009

A method in which continuous electric current is passed through food to heat it rapidly while maintaining quality is called

A

microwave cooking

B

irradiation

C

ohmic heating

D

sonication

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7

2009 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2009

The TDT value (minutes) at 110 °C is

A

35.1

B

25.8

C

12.9

D

21.9

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8

2010 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2010

Shelf-life of fish can be extended by chilling as it

A

reduces chemical activity of food constituents and increases biochemical activity

B

reduces water activity and increases biochemical reaction rate

C

reduces chemical and biochemical reactions in fish cells

D

destroys pathogenic microbes

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9

2010 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2010

9.5 g of corn flakes containing 5% moisture (wet basis) is oxidized completely to CO₂ and H₂O by ignition in a Bomb Calorimeter (as shown in the figure). The combustion increases the temperature of 2500 g of water from 15°C to 27°C. Assume that the heat capacity and latent heat of vaporization of water are 4.187 kJ kg^-1 K^-1 and 2257 kJ kg^-1, respectively. Neglect any sensible heat gain by water vapour. The calorific value of the flake is

A

18.28 kJ g^-1 (4.37 kcal g^-1)

B

9.79 kJ g^-1 (2.34 kcal g^-1)

C

14.04 kJ g^-1 (3.36 kcal g^-1)

D

22.43 kJ g^-1 (5.36 kcal g^-1)

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10

2010 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2010

D₀ value of a bacterium is determined by using two thin walled glass capillary tubes filled with same bacterial suspension in distilled water. The sealed capillaries are dipped in an oil bath maintained at 121°C and kept for 60 s and 135 s, respectively. These capillaries are cooled immediately in ice water. Number of survivors remained in the respective tubes are 2000 and 300.
The processing time (in minutes) to kill 99.999% of the bacteria in any food at 121°C will be

A

7.60

B

6.60

C

12.62

D

2.60

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11

2011 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2011

The F_o value, based on 12D concept using the D_o value of the above organism and a most likely spore load in the product of 100, will be

A

3.0 min

B

1.2 min

C

1.5 min

D

4.2 min

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12

2012 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2012

Thermal death time (TDT) of Clostridium botulinum at 121 °C is 2.78 min with a z-value of 10 °C. The TDT of the microorganism at 116 °C (in min) is

A

5.270

B

8.791

C

1.390

D

0.712

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13

2013 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2013

Thermal death of viable spores of Bacillus subtilis in a food sample follows a first order kinetics with a specific death rate constant of 0.23 min^-1 at 100 °C. The time (in minutes) required to kill 99% of spores in the food sample at 100 °C will be

A

10

B

20

C

23

D

60

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14

2015 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2015

Multiple effect evaporation leads to

A

reduction in operating cost and reduction in capital cost

B

increase in operating cost and increase in capital cost

C

increase in operating cost and reduction in capital cost

D

reduction in operating cost and increase in capital cost

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15

2015 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2015

Which one of the following is NOT a component of an evaporator?

A

Heat exchanger

B

Vacuum separator

C

Condenser

D

Cyclone separator

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16

2016 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2016

The D₁₂₁ and Z values for C. botulinum spores in canned food are 0.2 min and 10 °C respectively. Total time required in min, to reduce the spores from 10⁵ to 10³ at 111 °C is _____.

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17

2016 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2016

A fruit juice with a negligible boiling point rise is being evaporated using saturated steam at 121.1 °C in a triple effect evaporator having equal area in each effect. The pressure of the vapor in the last effect is 25.6 kPa absolute and the corresponding saturation temperature is 65.7 °C. The heat transfer coefficients are U₁ = 2760, U₂ = 1875 and U₃ = 1350 W m^-2 K^-1. The boiling point (°C) in the first effect is __.

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18

2018 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2018

Apple juice of 10% total solids (TS) is being concentrated in a single effect evaporator working with a surface condenser to 40% TS under a vacuum of 20 kPa. After some time the vacuum pump stops but the evaporation process continued. Choose the combination of possible implications from the following.
(P) Product quality is affected
(Q) Substantial increase in thermal energy requirement
(R) Decrease in the rate of evaporation

A

P & Q

B

Q & R

C

R & P

D

P, Q & R

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19

2019 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2019

Sticking of powder to wall of the chamber during spray drying of fruit juice is due to ____.

A

Low glass transition temperature of the compounds in juice

B

High glass transition temperature of the compounds in juice

C

Improper processing parameters of spray dryer

D

Presence of gums in feed material

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20

2020 · Engineering Sciences · Food Engineering · Thermal operations

Engineering Sciences (XE) 2020

During extrusion cooking, food materials are generally subjected to a combination of

A

high shear and low pressure

B

high temperature and high shear

C

low shear and high temperature

D

low shear and low pressure

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