Deck 30: Food Microbiology

Question 1

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

A) 1800
B) 1850
C) 1900
D) 1920
E) 1985

Answer 1

C

Question 2

Pure water has a water activity value of ________.

A) 1.00
B) 0.80
C) 0.70
D) 0.90
E) 100

Answer 2

A

Question 3

Human disease(s) from milk may include

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

Answer 3

E

Question 4

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

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

Question 5

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.

Question 6

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.
E) respiratory illness.

Question 7

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

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

Question 8

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

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

Question 9

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

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

Question 10

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

Question 11

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

A) Fungi
B) Bacteria
C) Viruses
D) Protozoa
E) Fungi AND bacteria

Question 12

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

A) Bread
B) Jam
C) Salty ham
D) Milk
E) Bread and jam

Question 13

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

A) Cake
B) Jam
C) Syrup
D) Bread
E) Steak

Question 14

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 15

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

A) low.
B) high.
C) dense.
D) osmotic.
E) All of the answer choices are correct.

Question 16

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

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

Question 17

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

A) Pseudomonas species
B) Staphylococcus aureus
C) Most yeasts
D) Streptococcus pyogenes
E) E. coli

Question 18

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

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

Question 19

For growth, most bacteria require water activity levels above

A) 1.00.
B) 0.80.
C) 0.70.
D) 0.90.
E) 100.

Question 20

Which of the following organisms may grow at pH 3.5?

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

Question 21

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

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

Question 22

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

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

Question 23

Which of the following does NOT produce lactic acid?

A) Lactobacillus
B) Leuconostoc
C) Streptococcus
D) Lactococcus
E) Escherichia

Question 24

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.
E) hydrochloric acid.

Question 25

Naturally occurring antimicrobial chemicals may include

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

Question 26

The most prevalent cause of wine spoilage is the presence of

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

Question 27

The malolactic fermentation of wine is performed by

A) Lactobacillus species.
B) Saccharomyces species.
C) Leuconostoc species.
D) Aspergillus species.
E) acetic acid bacteria.

Question 28

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

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

Question 29

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

A) boiled at least 15 minutes before consumption.
B) frozen for 1 hour before consumption.
C) dried prior to eating.
D) eaten with spoons.
E) irradiated for 60 minutes before consumption.

Question 30

In a cow's udder, milk

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

Question 31

Soy sauce is made by fermentation of soybeans and wheat by

A) lactic acid bacteria.
B) Saccharomyces species.
C) Aspergillus species.
D) lactic acid bacteria AND Saccharomyces species.
E) lactic acid bacteria, Aspergillus species, AND Saccharomyces species.​

Question 32

Egg white is rich in the antimicrobial

A) lysosome.
B) allicillin.
C) lysozyme.
D) benzoic acid.
E) hydrogen peroxide.

Question 33

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 of spicy sausage.
D) counteract the action of the salt in the sausage.
E) remove water from the surface of the meat.

Question 34

Most bacteria are inhibited by a pH of

A) 7.2.
B) 7.0.
C) 6.0.
D) 4.5.
E) 6.5.

Question 35

Lactic acid bacteria are used to ferment and produce foods/beverages from all of the following EXCEPT

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

Question 36

Foods such as acidic fruits are often spoiled by

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

Question 37

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 38

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

A) Mesophiles
B) Psychrophiles
C) Thermophiles
D) Acidophiles
E) Hyperthermophiles

Question 39

Most human pathogens grow best at temperatures near

A) 20ºC.
B) 25ºC.
C) 37ºC.
D) 45ºC.
E) 97ºF.

Question 40

Staphylococcus aureus toxin is

A) heat-stable AND an endotoxin.
B) heat-stable AND an exotoxin.
C) an exotoxin AND heat-sensitive.
D) an endotoxin AND heat-sensitive.
E) None of the answer choices is correct.

Question 41

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 basically 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) It doesn't. Every fermenting microbe ferments the same way, producing the same products. Whatever we start with, the outcome is the same.
E) None of these explains why we would use known starter cultures.

Question 42

Lactobacillus acidophilus can potentially colonize the intestinal tract.

Question 43

The toxin causing botulism is classified as a(n)

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

Question 44

Which of the following is often associated with poultry products?

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

Question 45

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

Question 46

The bacteria associated with hemolytic uremic syndrome is

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

Question 47

The toxin produced by Staphylococcus aureus is heat-stable.

Question 48

Yeast alone cannot convert grain to alcohol.

Question 49

Clostridium botulinum toxin is

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

Question 50

What is the difference between fermented food and spoiled food?

A) Fermented foods are made using certain genera of bacteria only. Spoilage of food involves bacteria, molds, AND yeasts.
B) Fermented foods are changed by microbes but are edible. Spoiled foods are also changed by microbes but are full of microbial toxins that always lead to illness.
C) Fermented foods may change in appearance but they taste the same as non-fermented foods. Spoiled foods look the same as unspoiled foods but they taste different.
D) Fermented foods are intentionally altered during production by carefully controlling the activity of bacteria, yeasts, or molds. Spoiled foods have microbe-induced changes that are undesirable.
E) Fermented foods result from undesirable changes made by microbes. Spoiled foods result from desirable changes made by the same types of microbes.

Question 51

Aflatoxin is a potent carcinogen produced by certain bacteria.

Question 52

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

Question 53

Egg white is rich in the antimicrobial lysosome.

Question 54

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 55

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.

Question 56

You are cleaning out your pantry and find that your bread has spoiled. Which organism caused the spoilage, and why?

A) Bread is spoiled by bacteria because it does not have enough water available for mold growth.
B) Bread is spoiled by mold because it does not have enough water available for bacterial growth.
C) Bread is spoiled by mold because there is too much water present for bacterial growth.
D) Bread is spoiled by both bacteria and mold simultaneously-these organisms always act synergistically in spoilage.
E) Pseudomonas aeruginosa-this bacterium is the primary cause of spoilage in grain products.

Question 57

Foodborne intoxication requires the ingestion of living organisms.

Question 58

Please select the definition that is INCORRECT.

A) Foodborne intoxication-an illness that results from consuming a food product contaminated with microbes that colonize the host and cause disease.
B) Water activity (aw)-the relative amount of water available for microbial growth; pure water has an aw of 1.0.
C) Intrinsic factors-in food microbiology, the natural characteristics of a food that influence the rate of microbial growth.
D) Food preservation-increasing the shelf life of foods by preventing the growth and activities of microorganisms.
E) Fermented foods-foods intentionally altered during production by encouraging the activity of bacteria, yeasts, or molds.

Question 59

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

Question 60

Which strain of Escherichia coli may be involved in foodborne infection?

A) HB101
B) O157:H7
C) M309
D) AB220
E) O7:H157

Question 61

Which statement regarding canning and pasteurization is TRUE?

A) Pasteurization uses a process that destroys all microorganisms that can grow under normal storage conditions; the resulting product is commercially sterile. Canning significantly decreases the number of spoilage microbes and eliminates pathogens; however, viable organisms still remain.
B) Canning and pasteurization both significantly decrease the number of spoilage microbes and eliminates pathogens; however, viable organisms still remain.
C) Canning and pasteurization both use a process that destroys all microorganisms that can grow under normal storage conditions; the resulting products are commercially sterile.
D) Canning and pasteurization are essentially the same process-one is used on fresh food while the other is used on preserved food; both result in sterilization of the product.
E) Canning uses a process that destroys all microorganisms that can grow under normal storage conditions; the resulting product is commercially sterile. Pasteurization significantly decreases the number of spoilage microbes and eliminates pathogens; however, viable organisms still remain.

Question 62

What is the purpose of the mashing step in beer making?

A) During mashing, the enzymes of malted barley degrade fermentable sugars, converting them to starches.
B) Mashing increases the surface area available for microbes to adhere to during the fermentation process.
C) Mashing is required to remove residual solids, leaving wort that can be fermented by bacteria.
D) During mashing, the enzymes of malted barley degrade starches, converting them to fermentable sugars.
E) All of the answer choices are correct.

Question 63

Why might the presence of Apsergillus flavus in grain products be a problem?

A) All species of Aspergillus produce aflatoxin, a potent carcinogen.
B) Some species of Aspergillus produce aflatoxin, a potent carcinogen.
C) Some species of Aspergillus produce aflatoxin, which kills plants and causes crop loss.
D) Some species of Aspergillus cause systemic infections in animals that consume them.
E) Presence of Aspergillus indicates a highly contaminated environment.

Question 64

Which of the following is not an intrinsic factor affecting growth of microorganisms on food?

A) Water availability
B) Benzoic acid
C) Lysozyme
D) Temperature
E) Fruit rinds

Question 65

Why do bacteria generally predominate on fresh meats?

A) Fresh meat provides a moist, acidic, salty, nutrient-rich environment.
B) Most bacteria obtain iron from red blood cells-these are abundant in meat.
C) Fresh meat provides a moist, pH-neutral, nutrient-rich environment.
D) Fresh meat provides a somewhat dry, pH-neutral, saline environment that bacteria prefer.
E) The preservatives found on fresh meat stimulate the growth of bacteria.

Question 66

Why would the home-canned green beans rather than the tomato-beef stew be a possible source of C. botulinum?

A) Beans are low-acid. Any C. botulinum endospores that survived the home-canning process could germinate in the cans, giving rise to vegetative cells that produce botulinum toxin.
B) Canning creates an anaerobic environment. Any spores surviving the canning process could germinate, giving rise to vegetative cells that produce botulinum toxin.
C) The acidic pH of the tomato-beef stew would likely inhibit that growth of vegetative Clostridium botulinum cells. Low-acidity beans would not inhibit the growth of these cells.
D) The tomato-beef stew was not canned. The presence of oxygen in this food would prevent the growth of Clostridium botulinum, which is a obligate anaerobe.
E) All of the answer choices are correct.

Question 67

Under what conditions would the patient's stool sample be cultured in order to detect Clostridium botulinum?

A) Anaerobic, body temperature, neutral pH
B) Aerobic, body temperature, neutral pH
C) Anaerobic, refrigerator temperature, low acidity
D) Aerobic, refrigerator temperature, high acidity
E) Aerobic or anaerobic, body temperature, low acidity

Question 68

Why is ham is a common vehicle for S. aureus food poisoning?

A) S. aureus is part of the normal microbiota of cows, so is a frequent cause of S. aureus food poisoning.
B) Staphylococci are adapted to salty conditions and thrive with little competition on cured meats such as ham.
C) Staphylococci are able to act synergistically with the normal microbiota of pigs, creating toxins that result in food poisoning.
D) Ham is a particularly moist meat, so encourages the growth of the staphylococci, which can only survive on foods with a high aw.
E) Ham is an untreated raw meat. As such, it is prone to contamination by the staphylococci that thrive on meat, resulting in food poisoning.

Question 69

Why is botulism primarily a problem in canned foods rather than fresh ones?

A) Canned food is never sterilized, so bacteria such as C. botulinum thrive in cans.
B) Fresh food contains normal microbiota that prevents the growth of pathogens such as C. botulinum.
C) The canning process dramatically reduces the pH of food, and C. botulinum is an acidophile.
D) The causative agent is an obligate anaerobe-the canning process removes O2.
E) All of the answer choices are correct.

Question 70

Please select the statement that does NOT apply to botulism.

A) The causative agent is Clostridium botulinum.
B) Clostridium endospores can germinate in food with an acidic pH.
C) Vegetative Clostridium cells release botulinum toxin, a potent neurotoxin.
D) The causative agent is an obligate anaerobe.
E) Boiling home-canned foods for 10 minutes will destroy any botulinum toxin present.

Question 71

How did the antitoxin help the patient?

A) The antitoxin is a mixture of antigens that bind to and thereby neutralize the different serotypes of botulinum toxin.
B) The antitoxin binds to and destroys Clostridium botulinum cells, preventing them from releasing botulinum toxin.
C) The antitoxin is a mixture of antibodies that bind to and thereby neutralize the different serotypes of botulinum toxin.
D) The antitoxin contains antibodies to botulinum toxin type A, which is the type that causes illness.
E) The antitoxin stimulates phagocytes to neutralize botulinum toxin type A.