Deck 31: Food Microbiology

Question 1

The amount of moisture available in foods is designated by the term

A) fluid availability.
B) water activity.
C) dampness quotient.
D) aqueous usability.

Answer 1

B

Question 2

The growth of microorganisms in a food product is influenced by the availability of

A) moisture.
B) acidity.
C) nutrients.
D) temperature.
E) All of the choices are correct.

Answer 2

E

Question 3

The conditions normally present in food such as moisture, acidity and nutrients are referred to as

A) extrinsic factors.
B) intrinsic factors.
C) endogenous factors.
D) exogenous factors.

Answer 3

B

Question 4

Pure water has a water activity value of

A) 1.00.
B) 0.80.
C) 0.70.
D) 0.90.

Question 5

The connection between unpasteurized milk and brucellosis in humans was made by

A) Evans.
B) Pasteur.
C) Koch.
D) Fleming.

Question 6

Which of the following organisms may grow at pH 3.5?

A) Clostridium
B) Streptococcus
C) fungi
D) lactic acid bacteria
E) fungi AND lactic acid bacteria

Question 7

Which of the following organisms can grow at a lower water activity than most spoilage bacteria?

A) Pseudomonas sp.
B) most yeasts
C) Streptococcus pyogenes
D) Staphylococcus aureus

Question 8

Which of the following are most likely to be found growing on salted or dried foods?

A) fungi
B) bacteria
C) viruses
D) protozoa

Question 9

Which of the following foods has the greatest amount of available water?

A) cake
B) steak
C) jam
D) syrup

Question 10

On which of the following foods can Staphylococcus aureus multiply with little competition?

A) bread
B) salty ham
C) jam
D) milk

Question 11

Lactic acid bacteria

A) consume lactic acid, allowing them to grow on foods such as yogurt.
B) produce lactic acid, allowing them to produce foods such as yogurt.
C) are important spoilage organisms.
D) can grow on lemons.
E) produce lactic acid, allowing them to produce foods such as yogurt AND are important spoilage organisms.

Question 12

Which of the following organisms may grow at pH 2.2?

A) Clostridium
B) Streptococcus
C) fungi
D) lactic acid bacteria
E) fungi AND lactic acid bacteria

Question 13

Clostridium botulinum typically does not produce its toxin under conditions that are

A) anaerobic.
B) alkaline.
C) neutral.
D) acid.

Question 14

Foods that have been altered due to the carefully controlled growth of microorganisms are called

A) cooked.
B) controlled.
C) preserved.
D) fermented.

Question 15

Human disease(s) from milk may include

A) brucellosis.
B) anthrax.
C) amoebiasis.
D) tuberculosis.
E) brucellosis AND tuberculosis.

Question 16

For growth, most bacteria require water activity levels above

A) 1.00.
B) 0.80.
C) 0.70.
D) 0.90.

Question 17

The water activity in foods that have high levels of salt or sugar is

A) high.
B) dense.
C) low.
D) osmotic.

Question 18

Growth of pathogens in a food generally does not result in perceptible changes in the quality of the food but the ingestion of this food can result in

A) spoilage.
B) foodborne illness.
C) aging.
D) toxin infection.

Question 19

Foods that have been unacceptably altered due to uncontrolled bacterial growth are called

A) refrigerated.
B) spoiled.
C) preserved.
D) fermented.

Question 20

Most large cities have required the pasteurization of milk and milk products since

A) 1800.
B) 1850.
C) 1900.
D) 1920.

Question 21

Sugar is used in the making of fermented sausages to

A) help preserve the sausage.
B) provide raw material for the fermentation process.
C) sweeten the taste.
D) counteract the action of the salt in the sausage.

Question 22

Most bacteria are inhibited by a pH of

A) 7.2.
B) 7.0.
C) 6.0.
D) 4.5

Question 23

Most human pathogens grow best at temperatures near

A) 20ºC.
B) 25ºC.
C) 37ºC.
D) 45ºC.

Question 24

Foods such as acidic fruits are often spoiled by

A) fungi.
B) protozoans.
C) viruses.
D) bacteria.

Question 25

Naturally occurring microbial chemicals may include

A) benzoic acid.
B) lysozyme.
C) allicin.
D) peroxidase.
E) All of the choices are correct.

Question 26

The unique flavor of yogurt is due to the production of

A) lactic acid and acetaldehyde.
B) casein and alcohol.
C) rennin and coagulated protein.
D) curd and whey.

Question 27

Soy sauce is made by fermentation of soybeans and wheat by

A) lactic acid bacteria.
B) Saccharomyces.
C) Aspergillus.
D) lactic acid bacteria AND Saccharomyces.

Question 28

S. aureus toxin is

A) heat-stable.
B) an exotoxin.
C) an endotoxin.
D) heat-sensitive.
E) heat-stable AND an exotoxin.

Question 29

The malolactic fermentation of wine is performed by

A) Lactobaccilus.
B) Saccharomyces.
C) Leuconostoc.
D) Aspergillus.

Question 30

Which of the following is most likely to grow at refrigerator temperatures?

A) mesophiles
B) psychrophiles
C) thermophiles
D) acidophiles

Question 31

The most prevalent cause of wine spoilage is the presence of

A) sulfur dioxide.
B) carbon dioxide.
C) acetic acid bacteria.
D) ethanol.

Question 32

Which of the following produce lactic acid?

A) Lactobacillus
B) Leuconostoc
C) Streptococcus
D) Lactococcus
E) All of the choices are correct.

Question 33

Slow cooking for a long time and then storage at room temperature would tend to favor the growth of

A) endospore-formers.
B) anaerobes.
C) mesophiles.
D) thermophiles.
E) endospore-formers AND mesophiles.

Question 34

The final characteristics of beer such as color, flavor, and foam primarily depend on the

A) roasted malt.
B) adjuncts.
C) wort.
D) whey.

Question 35

In a cow's udder, milk

A) contains Lactococcus.
B) contains Lactobacillus.
C) is acidic.
D) is sterile.

Question 36

Limiting the activity of microbes in food can be accomplished by

A) pasteurization.
B) cold storage.
C) lowering the pH.
D) growth inhibiting substances.
E) All of the choices are correct.

Question 37

The resulting solids and juices of grapes used to make wine are termed its

A) mash.
B) must.
C) germinater.
D) malt.

Question 38

Egg white is rich in the antimicrobial

A) lysosome.
B) RNAse.
C) penicillin.
D) lysozyme.

Question 39

Lactic acid bacteria are used to ferment and produce foods from

A) dairy.
B) vegetables.
C) meat.
D) All of these can be fermented by lactic acid bacteria to make foods.

Question 40

The tart taste of yogurt, pickles and sharp cheeses is due to the presence of

A) lactic acid.
B) acetic acid.
C) sorbic acid.
D) benzoic acid.

Question 41

Yeast cannot convert grain to alcohol.

Question 42

Egg white is rich in the antimicrobial lysosome.

Question 43

The water activity in foods with high levels of salt or sugar is high.

Question 44

Aflatoxin is a potent carcinogen produced by certain bacteria.

Question 45

C. botulinum toxin is

A) heat-stable.
B) an exotoxin.
C) endotoxin.
D) heat-sensitive.
E) an exotoxin AND heat-sensitive.

Question 46

Lactobacillus acidophilus can potentially colonize the intestinal tract.

Question 47

Which of the following is often associated with poultry products?

A) Salmonella
B) Campylobacter
C) Pseudomonas
D) Lactobacillus
E) Salmonella AND Campylobacter

Question 48

The most promising sources of single cell protein are bacteria.

Question 49

Why would the use of a known, reliable starter culture improve the safety of fermented meat products?

A) It doesn't. All fermented meat products are inherently unsafe since we can't determine what fermentation products are left behind in the food. Some of them may be toxic.
B) By using pure starter cultures, we KNOW what we're adding in, and how much. We can control the microbial fermentation precisely to best prepare the food product.
C) We need to be very careful which microbes are introduced into a food product. Some microbes can interact with microbes already present in the food, producing toxins and toxic byproducts that might harm human beings.
D) Not every fermenting microbe ferments the same way. Even different strains of the same species might produce different products. Some of these products might not be safe for human consumption.
E) By using pure starter cultures, we KNOW what we're adding in, and how much. We can control the microbial fermentation precisely to best prepare the food product AND not every fermenting microbe ferments the same way. Even different strains of the same species might produce different products. Some of these products might not be safe for human consumption.

Question 50

Irradiation of foods

A) involves the use of gamma radiation.
B) is used on all foodstuffs.
C) changes the taste of foods.
D) is not regulated by the government.
E) involves the use of gamma radiation, changes the taste of foods AND is not regulated by the government.

Question 51

The toxin produced by S. aureus is heat-stable.

Question 52

The most promising sources of single cell protein are

A) bacteria.
B) viruses.
C) worms.
D) yeasts.

Question 53

As an added safety precaution, low-acid, home canned foods should be

A) eaten with spoons.
B) boiled at least 15 minutes before consumption.
C) frozen for 1 hour before consumption.
D) dried prior to eating.

Question 54

The bacteria associated with hemolytic uremic syndrome is

A) Salmonella cholerasuis.
B) Campylobacter jejuni.
C) Pseudomonas aeruginosa.
D) Lactobacillus.
E) Escherichia coli O157:H7.

Question 55

High concentrations of nucleic acids in the diet may lead to high levels of uric acid in the blood.

Question 56

The toxin of botulism is classified as a(n)

A) enterotoxin.
B) endotoxin.
C) neurotoxin.
D) toxoid.

Question 57

Single cell protein

A) refers to the use of single-celled organisms as a protein source.
B) refers to a single-protein produced by several different organisms.
C) is an enzyme.
D) causes food intoxication.

Question 58

Which strain of

A) HB101
B) M309
C) AB220
D) O157:H7
E) coli may be involved in foodborne infection?

Question 59

Foodborne intoxication requires the ingestion of living organisms.

Question 60

The bacteria associated with hemolytic uremic syndrome is Escherichia coli O157:H7.

Question 61

Why might a large number of competing microorganisms in a food sample result in lack of sensitivity of culture methods for detecting pathogens?

A) Many microbes secrete compounds that can be toxic for their competitors. If you need a pathogenic microbe to grow in a culture in order to detect it, these toxic compounds might inhibit the growth of the pathogen and impede the test.
B) You can't obtain a pure culture from a food sample that has a large number of microbes present. It would be impossible to detect only one from within the sample.
C) Culture methods often rely on biochemical changes taking place in medium for identification. With multiple microbes present, you may not be sure that the biochemical change observed is from the presence of a pathogen or from some other non-dangerous bacterium that also induces the biochemical change.
D) The sheer number of microbes present might shut down the growth/replication of a pathogenic microbe in a food sample due to a 'starving out' effect. If it can't grow/replicate, it won't be detectable by a culturing method test.
E) Many microbes secrete compounds that can be toxic for their competitors. If you need a pathogenic microbe to grow in a culture in order to detect it, these toxic compounds might inhibit the growth of the pathogen and impede the test AND culture methods often rely on biochemical changes taking place in medium for identification. With multiple microbes present, you may not be sure that the biochemical change observed is from the presence of a pathogen or from some other non-dangerous bacterium that also induces the biochemical change.