This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Microbial Flora of Fresh Foods”.
1. Which of the following organism occurs on the skin of fresh poultry?
a) pseudomonads
b) staphylococci
c) micrococci
d) enterococci
View Answer
Explanation: Pseudomonads constitute the major contaminants on the skin of freshly dressed poultry.
2. What is the pH of the bananas?
a) 2.3
b) 5.0
c) 7.0
d) 12.0
View Answer
Explanation: The pH of fruits is relatively acid ranging from 2.3 for lemons to 5.0 for bananas. This restricts bacterial growth but does not retard fungal growth.
3. Raw milk of good sanitary quality will develop sweet flavour.
a) True
b) False
View Answer
Explanation: Raw milk of good sanitary quality will develop a clean, sour flavour. This change is brought about mainly by Streptococcus lactis and S.cremoris.
4. At what temperature pasteurization of milk takes place?
a) 650 C
b) 370 C
c) 62.80 C
d) 450 C
View Answer
Explanation: The holding method of pasteurization exposes milk to a temperature of 62.80 C for 30 mins.
5. Which among the following is a gas producer organism?
a) Streptococcus lactis
b) Lactobacillus fermentum
c) Micrococcus luteus
d) Clostridium butyricum
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Explanation: Clostridium butyricum causes fermentation of lactose with accumulation of gas. The gas may be a mixture of carbon dioxide and hydrogen or only carbon dioxide in case of yeast fermentation.
6. Which among the following group of microorganisms are found in the ducts of cow’s mammary glands?
a) Coliforms
b) Lactobacilli
c) Micrococci
d) Microbacteria
View Answer
Explanation: Micrococci such as Micrococcus luteus, Micrococcus varians are found in the ducts of cow’s mammary glands and dairy utensils. They are acid producers and are weakly proteolytic.
7. The coloration of the milk is caused by which of the following organism?
a) Pseudomonas sp.
b) Bacillus sp.
c) Penicillium sp.
d) Streptococcus sp.
View Answer
Explanation: Pseudomonas sp. may produce coloration of milk. End products of proteolysis may impart abnormal flavor or odor to the milk.
8. In which of the following biochemical types of microorganisms a slime layer or capsule is formed on the cells?
a) Acid producers
b) Gas producers
c) Ropy or stringy fermentation
d) Proteolytic
View Answer
Explanation: In Ropy or stringy fermentation, organisms synthesize a viscous polysaccharide material that forms a slime layer or capsule on the cells. They include Alcaligenes viscolactis, Enterobacter aerogenes, etc.
9. Tuberculosis brucellosis is caused by the pathogen from an infected cow.
a) True
b) False
View Answer
Explanation: Pathogen from infected cow are transmitted through milk to humans or cow and causes tuberculosis brucellosis, mastitis.
10. Which of the following type of spoilage occurs in fresh meat?
a) Souring
b) Greening
c) Putrefaction
d) Moldy
View Answer
Explanation: Fresh meat is spoiled by putrefaction and is caused by Alcaligenes, Clostridium, Proteus vulgaris etc. In putrefaction, the protein foods are degraded by proteolytic microorganisms to give amino acids, amines, ammonia and hydrogen sulphide.
11. Spoilage of bread is caused by which of the following microorganism(s)?
a) Saccharomyces
b) Rhizopus
c) Leuconostoc
d) Pseudomonas
View Answer
Explanation: Moldy and ropy type of spoilage occurs in bread which are caused by Rhizopus nigricans, Penicillium, Aspergillus niger and Bacillus subtilis.
12. The thermophilic anaerobe spoilage of low and medium acid canned products are caused by _____________
a) Bacilllus stearothemophilus
b) Clostridium thermosaccharolyticum
c) Bacillus thermoacidurans
d) Clostridium sporogenes
View Answer
Explanation: Thermophilic anaerobe spoilage of low and medium acid canned products such as corn, peas, spinach are caused by Clostridium thermosaccharolyticum. It can swells and may burst.
Sanfoundry Global Education & Learning Series – Microbiology.
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