This set of Food Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Microorganisms Growth Factors – Radiation”.
1. The primary target of ionizing radiation is _______
a) Cell wall
b) Ribosomes
c) Genetic material
d) Golgi bodies
View Answer
Explanation: The ionizing radiation primarily targets DNA. This is why microbes with smaller genomes are more resistant to radiation. The radiation mutates and cleaves DNA to prevent microbial growth.
2. _______ causes damage to DNA during radiation.
a) Hydrogen
b) Hydroxyl radicle
c) Nitrites
d) Carbon dioxide
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Explanation: Reactive Oxygen Species (ROS) such as hydroxyl radicles and superoxide anions are produced when the microbes are exposed to radiation. Different microbes have different capacities to produce these and hence their sensitivity differs. These species cause DNA damage and cell death.
3. Gram-negative bacteria are more sensitive to radiation than Gram-positive bacteria.
a) True
b) False
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Explanation: Gram-negative bacteria have a thinner outer wall as compared to Gram-positive bacteria. The thicker wall of the Gram-positive bacteria provides more resistance against the radiation.
4. Applying high-dose irradiation to sterilize food is called ___________
a) Lethal dosing
b) Radappertization
c) Radicidation
d) Radurization
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Explanation: Radapperization is when high-dose irradiation is provided for commercial sterilization. This inactivates spores too. Radicidation is medium-dose irradiation to inactivate vegetative bacterial cells. Radurization is low-dose irradiation used to delay the ripening of fruits etc.
5. What is the uniformity of dose distribution when Dmax = 50 and Dmin = 10?
a) 500
b) 60
c) 5
d) 40
View Answer
Explanation: The food absorbs radiation when it passes through a radiation chamber. Hence, the packets closer to the source may receive a larger dose. To take care of this, a parameter called uniformity of dose distribution is defined.
Uniformity of dose distribution = Dmax/Dmin
Hence Uniformity = 50/10 = 5
6. What instrument is used to monitor the amount of irradiation received by the food?
a) Radometer
b) X Ray
c) Dosimeter
d) Radiometer
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Explanation: Dosimeter is used to measure and monitor the amount of radiation received by a food. Dosimeters have to be sensitive to irradiation and are usually made of photographic films. They can be placed in the food packages to do their job.
7. What is the unit of the absorbed dose of ionizing radiation?
a) Curie
b) Becquerel
c) It has no unit
d) Gray
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Explanation: One Gray is the absorption of one Joule of radiation energy per kg of matter. Curie (Ci) and Becquerel (Bq) are units of radioactivity. Gray and Dose are units of the amount of radiation absorbed.
8. The resistance of microbes to irradiation is inversely proportional to the temperature.
a) True
b) False
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Explanation: This can be due to the reduction in water activity and in the mobility of free radicles. Hence, lower temperatures minimize the effect of radiation on the chemical components of food.
9. Microbes are less sensitive in _______ containing media rather than in buffer solutions.
a) Salts
b) Lipids
c) Proteins
d) Carbohydrates
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Explanation: For a strain of a certain bacterium, the D value of radiation was 3kGY in a cooked meat broth whereas it was 0.23 in a phosphate buffer solution. Proteins provide protection from ionizing radiation as well as from certain chemicals and heat.
10. The radiation resistance of dry cells is _____ compared to moist cells.
a) Equal to
b) Lesser
c) Not Related
d) Higher
View Answer
Explanation: The radiation resistance of moist cells is less than that of dry cells. This may be due to the radiolysis of water by ionizing radiation.
11. The resistance of the microbes is highest in the _____ phase.
a) Lag
b) Log
c) Stationary
d) Death
View Answer
Explanation: Microbes tend to try to adapt themselves according to the environment in the lag phase. The microbial cells mature and do not actively divide. The radiation sensitivity increases as the cells enter and grow through the log phase.
Sanfoundry Global Education & Learning Series – Food Microbiology.
To practice all areas of Food Microbiology, here is complete set of Multiple Choice Questions and Answers.
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