This set of Food Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Food Quality Analytical and Cultural Techniques”.
1. ______ is a useful indicator of faecal pollution in water.
a) Amoeba
b) Bacillus thuringiensis
c) E. coli
d) Clostridium
View Answer
Explanation: E. coli is naturally present in the gut of animals. It is present in the lower intestines of warm-blooded organisms. It is not found in pure water. Hence, its presence indicates faecal matter.
2. What is the full form of DEFT?
a) Direct Epifluorescent Filter Technique
b) Direct Efflorescence Filter Technique
c) Direct Epifluorescent Florescence Technique
d) Direct Efflorescence Fatal Technique
View Answer
Explanation: Direct Epifluorescent Filter Technique is a technique used for direct examination of microbes under a microscope. Bacteria can be differentiated using this technique. Acridine orange stain was used to do the same.
3. Bacterial endospores are easier to see with phase contrast microscopy.
a) True
b) False
View Answer
Explanation: Phase contrast microscopy depends on the changes in optical densities and phases. Bacterial endospores have a high refractive index. This is why phase contrast microscopy gives us a better look at them.
4. _________ is used to lyse cells.
a) Amylase
b) Trypsin
c) Invertase
d) Lipase
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Explanation: Trypsin is a protease. It is used to lyse somatic cells to separate them. Trypsinization also helps in the removal of adherent cells from a clump. This also prevents the clogging of filters.
5. The DEFT filter is stained with _____________
a) Methyl Red
b) Methylene Blue
c) Crystal Violet
d) Acridine Orange
View Answer
Explanation: Acridine orange is a florescent dye that can be used to detect cells. It stains the nucleic material in the live cells. It can be used to predict the cell cycle stage a cell is in.
6. When acridine orange binds to DNA it gives ________ color.
a) Yellow
b) Orange
c) Green
d) Red
View Answer
Explanation: Acridine orange gives a green color when it binds with DNA and red color when it binds with RNA. It differentiates between eukaryotes and prokaryotes by staining differently. Eukaryotes are stained green, whereas prokaryotes are orange.
7. What is the full form of CTC?
a) Cyanoditolyl tritium chloride
b) Cyanoditolyl trizolium chloride
c) Cyanoditolyl trichloride
d) Cyanoditolyl tetrazolium chloride
View Answer
Explanation: CTC is a viability stain. It emits color only if there is a functioning electron transport chain. This redox dye can be used to determine the metabolic activity of a microbes, especially the respiratory activity.
8. For DEFT, bacteria should be trapped in a single focal plane.
a) True
b) False
View Answer
Explanation: The microscope has limited depth of focus at the required magnification. A single focal plane can be maintained by using a polycarbonate membrane. Multiple focal planes may disrupt the results due to incomplete visualization of the bacteria.
9. What is the full form of FDA?
a) Fluorescein diacetate
b) Fluorescein dialkylate
c) Fluorine diacetate
d) Fluorescein diammonium
View Answer
Explanation: FDA is used as a dye to measure cell viability through their ability to produce enzymes. It gives out a bright-green glow. The activity is measured using a spectrofluorometer.
10. FDA emits color only if there is _______ activity.
a) Esterase
b) Luciferase
c) Invertase
d) Pepsin
View Answer
Explanation: Esterase activity cleaves the FDA to produce fluorescein which glows. This is possible in live cells only. This can be used to check the microbial activity in soil samples. It can also be coupled with propidium iodide to check cell viability.
11. Agar is obtained from ________
a) Fungi
b) Bacteria
c) Algae
d) Amoebae
View Answer
Explanation: Agar is a polysaccharide obtained from red algae. It comprises of agarose and agaropectin. It can be used as a solid substrate for microbial cultures as well as cell cultures. It can also be used as a vegetarian substitute to gelatin.
12. Agar is microbial hydrolysis resistant due to the presence of _________
a) L-galactose
b) D-galactose
c) L-mannose
d) D-mannose
View Answer
Explanation: L-galactose can inhibit the hydrolases produced by the microbes. Hence, it is resistant to microbial hydrolysis and it preferred for microbial growth.
13. Potato dextrose agar is used for ________
a) Bacteria
b) Fungi
c) Algae
d) Protozoa
View Answer
Explanation: The dextrose provides a simple carbohydrate substrate, whereas, the potato provides complex nutrient. The low pH inhibits microbes. This substrate is ideal for mold sporulation.
14. In Baird-Parker agar, the elective agent used is ________
a) Sodium tellurite
b) Lithium Chloride
c) Egg yolk
d) Sodium pyruvate
View Answer
Explanation: In Baird-Parker agar, sodium pyruvate is the elective agent. Sodium tellurite and Lithium chloride are selective agents, whereas egg yolk is a diagnostic feature.
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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