Food Processing Unit Operations Questions and Answers – Heat Transfer Applications – Thermal Processing

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This set of Food Processing Unit Operations Multiple Choice Questions & Answers (MCQs) focuses on “Heat Transfer Applications – Thermal Processing”.

1. Which describes the level of microbial destruction obtained by thermal treatment?
a) F0 value
b) Thermal death time
c) D value
d) Z value
View Answer

Answer: a
Explanation: The level of microbial destruct that is obtained by thermal treatment is known as sterilizing value (F0) of the given food product. The results are calculated at 121.1°C temperature. The unit is minutes.

2. ________ relates the resistance of an organism to differing temperatures.
a) F0 value
b) Thermal death time
c) D value
d) Z value
View Answer

Answer: d
Explanation: Z- value is defined as the temperature (in degree) at which a tenfold reduction in D-value is attained. The main application of Z- value is in the calculating the thermal death time of a microorganism.

3. _________ is defined as the time taken at a given temperature to eliminate at least 90% of the exposed microorganisms.
a) F0 value
b) Thermal death time
c) D value
d) Z value
View Answer

Answer: c
Explanation: D valueis defined as the time taken at a given temperature to eliminate at least 90% of the exposed microorganisms. It is suitable to examine the efficiency of thermal inactivation of different microbes under different conditions.
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4. ________ is the time taken to kill a specific bacterium at a specific temperature.
a) F0 value
b) Thermal death time
c) D value
d) Z value
View Answer

Answer: b
Explanation: Thermal death time which is also known as TDT is defined as the time taken to destroy a specific microbe at a particular temperature. TDT is used in regulating the sterilization procedures.

5. _______ of a microorganism is the lowest temperature at which all microbes are killed in a 10-minute exposure.
a) F0 value
b) Thermal death time
c) D value
d) Thermal death point
View Answer

Answer: d
Explanation: Thermal death point is be defined as the lowest temperature at which all the microorganisms are killed in a 10-minute exposure and it varies depending on the microbes. Thermal death point gives the idea of the effect of heat on the microbes.

6. Are these statements about the D value true?
Statement 1: D -value is lower in acid foods.
Statement 2: D-value for the same organism varies depending on the food type.
a) True, False
b) True, True
c) False, True
d) False, False
View Answer

Answer: b
Explanation: D value is defined as the time taken at a given temperature to eliminate at least 90% of the exposed microorganisms. It is suitable to examine the efficiency of thermal inactivation of different microbes under different conditions. D-value for the same microbes differs depending on the food type. In acid foods, the D value is lower and higher in protein rich foods.

7. __________ is used mainly in low acid canned foods.
a) 12 D concept
b) 1 D concept
c) 10 D concept
d) 100 D concept
View Answer

Answer: a
Explanation: 12D concept is used generally in low acid canned foods. It refers to thermal processing to reduce the probability of survival of the C. botulinum spores to 10-12 which is high resistant microbe at 121oC.
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8. ______ is the better way of stating thermal death time.
a) F0 value
b) F value
c) D value
d) Z value
View Answer

Answer: b
Explanation: Thermal death time which is also known as TDT is defined as the time taken to destroy a specific microbe at a particular temperature. F value is defined as the time required killing all spores or vegetative cells at 1210oC. Therefore F value is the better way of stating thermal death time.

9. _________ is equal to the reciprocal of the slope of the thermal death time curve.
a) F0 value
b) F value
c) D value
d) Z value
View Answer

Answer: d
Explanation: Z-value is used in the microbial thermal death time calculations. It is defined as the temperature (in degree) at which a tenfold reduction in D-value is attained. It is equal to the reciprocal of the slope of the thermal death time curve.
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10. Heat resistance of microorganisms and their spores can be expressed in terms of _______
a) F0 value
b) thermal death time
c) D value
d) thermal death point
View Answer

Answer: b
Explanation: Heat resistance of microorganisms and their spores can be expressed in terms of thermal death time. Microorganisms are more heat resistant than their spores. Heat resistance of ascospores is 60°C for 10-15 min and the heat resistant of vegetative yeast is 50-58°C in 10-15 min.

Sanfoundry Global Education & Learning Series – Food Processing Unit Operations.

To practice all areas of Food Processing Unit Operations, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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