250+ MCQs on Microbiology – Product Spoilage and Answers

Fermentation Technology Multiple Choice Questions on “Microbiology – Product Spoilage”.

1. Who edited the second edition of ‘Brewing Microbiology’?
A. Rainbow
B. Priest and Campbell
C. Dolezil and Kirsop
D. Fernandez and Simpsonid5fdc03eface55″

Answer: B
Clarification: Priest and Campbell in 1996 edited the second edition of the ‘Brewing Microbiology’. The multi-authored book contains the text which is a real treasure-trove of information about what remains the poor relation of brewing science.

2. ‘The Beer is resistant to the microbial spoilage’. Who noticed the phenomena?
A. Fernandez
B. Simpson
C. Rainbow
D. Priestid5fdc03eface7e”

Answer: C
Clarification: Rainbow in 1981 noticed that the beer is resistant to the microbial spoilage. It is because of its low nutritional status, it’s content of products of yeast metabolism, its adverse values of pH and redox potential and its content of hop bitter substances. This explains the robustness of the beer to microbial spoilage.

3. Who correlated the resistance of spoilage to the beer parameters?
A. Rainbow
B. Priest and Campbell
C. Dolezil and Kirsop
D. Fernandez and Simpsonid5fdc03efacea4″

Answer: D
Clarification: Fernandez and Simpson in 1995 correlated the resistance of spoilage to the beer parameters. They used 14 strains of hop-resistant lactic acid bacteria and 17 different lagers. The spoilage was related to beer pH, nutrients, and undissociated forms of hop bitter acids and Sulphur dioxide.

4. Which of the following is a laboratory test used to describe bacteria?
A. Ouchterlony test
B. RPR test
C. Catalase test
D. Coombs testid5fdc03efaceb0″

Answer: C
Clarification: The catalase test is used to describe bacteria and also can be used to add value in routine microbiological troubleshooting. The Gram’s test can also be used to describe the bacteria. RPR test, Ouchterlony test, and Coombs test are not used in describing bacteria and are used in the Antigen-Antibody reaction.

5. Who devised Gram’s test?
A. Hans Christian
B. Rainbow
C. Fernandez
D. Jacobid5fdc03efacebb”

Answer: A
Clarification: A Danish bacteriologist, Hans Christian Gram in 1884 devised the Gram’s test who was working in the morgue in Berlin. Those bacteria which stain purple in color are Gram-positive bacteria and those which stain red or pink are Gram-negative bacteria.

6. Which of the following is a Gram-positive bacteria?
A. Acetobacter aceti
B. Escherichia coli
C. Gluconobacter oxydans
D. Streptococcus pneumoniaeid5fdc03efacec5″

Answer: D
Clarification: Streptococcus pneumoniae is a Gram-positive bacteria which take up purple stain from crystal violet when observed under the microscope. Other three bacteria belong to Gram-negative as they are observed as a pink stain when observed in the microscope.

7. Which of the following is used in the Gram’s staining?
A. Methylene blue
B. Safranin
C. Phenolphthalein
D. Methyl orangeid5fdc03efacecf”

Answer: B
Clarification: Safranin is used in Gram’s staining procedure. If it is a Gram-negative bacteria, it stains red. If it is a Gram-positive bacteria, it stains purple. The safranin is a counterstain and is lighter than crystal violet. It does not disrupt the colouration in Gram-positive cells while it decolorizes Gram-negative cells.

8. Who gave the explanation for hop resistance?
A. Hammond
B. Simpson
C. Sami
D. Fernandezid5fdc03efaced8″

Answer: C
Clarification: Sami et al. in 1997 gave a promising explanation for hop resistance. The presence or absence of a plasmid gene hor A correlates with hop resistance or sensitivity.

9. Which of the following is not reclassified into Saccharomyces cerevisiae?
A. S. tubidans
B. S. willianus
C. S. diastaticus
D. S. bayanusid5fdc03efacee2″

Answer: D
Clarification: Saccharomyces bayanus is not reclassified into Saccharomyces cerevisiae as it has remained unscathed by taxonomic changes. Saccharomyces tubidans, Saccharomyces ellipsoideus, Saccharomyces willianus, Saccharomyces diastaticus are now reclassified as Saccharomyces cerevisiae.

10. The killer yeasts produce _____________
A. Endotoxins
B. Exotoxins
C. Neurotoxins
D. Enterotoxinsid5fdc03efaceec”

Answer: B
Clarification: The killer yeasts produce exotoxins or ‘zymocins’ (to which they are immune) that kill the susceptible cells belonging to the same species. The Saccharomyces killer yeasts have been identified and best understood.

11. Which of the following is a real enemy of process and product hygiene?
A. Sources
B. Nitrosamines
C. Biofilms
D. Biogenic Aminesid5fdc03efacef5″

Answer: C
Clarification: Biofilms are the real enemy of process and product hygiene in brewing. The Biofilms or Biosponge provide both protection and nutrients for micro-organisms which are hostile in inappropriate environments.

12. Which of the following is not a biofilm?
A. Dental plaque
B. Slimes
C. Biofouling
D. Biogenic Aminesid5fdc03efaceff”

Answer: D
Clarification: Biogenic Amines are not a biofilm. Dental plaque, Slimes in water pipes and drains, and biofouling in cooling towers and heat exchangers are the classical biofilms. The biofilms are almost everywhere.

13. There are two drivers for consumer awareness of food safety.
A. True
B. Falseid5fdc03efacf08″

Answer: A
Clarification: Two drivers have been identified for the consumer awareness of food safety. First, the sensitization of consumer through scares such as BSE in beef products, benzene in carbonated drinks, etc. Second, the rapid development of analytical detection.

14. Nitrosamines are powerful carcinogens.
A. True
B. Falseid5fdc03efacf12″

Answer: A
Clarification: Nitrosamines are powerful carcinogens in animal systems and there has been indirect evidence that they are also involved in the development of human cancers. It was reported by Long in 1999.