Deck 41: Microbiology of Food

Question 1

Microorganisms that grow in media with low water availability are called _____________.

Answer 1

xerophilic

Question 2

Lysozyme is an important antimicrobial substance found at high levels in which food?

A)Fish
B)Eggs
C)Vegetables
D)Fruits

Answer 2

B

Question 3

Growth of yeasts and molds will be favored in more acidic foods.

Answer 3

True

Question 4

A food spoilage process called __________ results in the release of foul-smelling amine compounds.

Question 5

The term radappertization is used to describe food preservation by _________.

A)heat
B)chemicals
C)UV irradiation
D)gamma irradiation

Question 6

Filtration is sometimes used to remove organisms from beer because it has less effect on the flavor than pasteurization.

Question 7

The first person to use heating processes to preserve foods was _________.

A)Louis Pasteur
B)Jacque Monod
C)Robert Koch
D)Nicholas Appert

Question 8

Gamma irradiation has been used to sterilize certain types of foods.There are,however,certain limitations on its effectiveness.One of these is that it will only work on

A)moist foods.
B)dry foods.
C)foods that are not in metal cans.
D)It is effective with all foods.

Question 9

Which of the following represents a different principle for food preservation?

A)Freeze-drying
B)Addition of salt
C)Smoking
D)Heating

Question 10

Which of the following can function better at lower pH?

A)Yeasts and molds
B)Bacteria
C)Viruses
D)Protozoa

Question 11

Atmosphere is important in food spoilage; high H₂S tends to reduce spoilage,while high CO₂ tends to increase spoilage.

Question 12

Which of the following represents ways in which canned foods may undergo spoilage?

A)Spoilage before canning
B)As a result of underprocessing during canning
C)Leakage of contaminated water through can seams during cooling
D)All of the choices are correct.

Question 13

Temperature and relative humidity are important intrinsic factors in determining the rate of food spoilage.

Question 14

Pasteurization of milk

A)is no longer used for food processing in the United States.
B)usually eliminates all disease-causing organisms.
C)is a method for sterilization of food items.
D)reduces microbial growth by decreasing availability of water.

Question 15

To control pathogenic and disease-causing organisms,spices can be fumigated using _________.

A)ammonium gas
B)heavy metals
C)ethylene oxide
D)chlorine gas

Question 16

Nisin

A)is a small amphiphilic peptide that disrupts membrane integrity and function.
B)is a food additive that blocks the growth of some gram positive bacteria.
C)is a bacteriocin produced by some strains of Lactococcus lactis.
D)All of the choices are correct.

Question 17

A major chemical used to preserve meat products is ________.

A)ethylene oxide
B)propionate
C)nitrite
D)refrigeration

Question 18

The use of plastic film to wrap meat products can result in increased surface growth of microorganisms in part because of exposure to

A)oxygen.
B)N₂,which comprises approximately 78% of gas in the atmosphere.
C)carbon dioxide.
D)water.

Question 19

A chemical that is effective in preserving foods with a low pH such as bread is ________.

A)sodium propionate
B)sodium nitrate
C)sodium citrate
D)sodium sulfite

Question 20

Which of the following helps preserve foods by controlling microbial access to water?

A)Drying
B)Addition of salt
C)Addition of sugar
D)All of the choices are correct.

Question 21

Sometimes __________ beams are used to irradiate foods in place of gamma radiation because the process does not generate radioactive waste.

A)microwave
B)electron
C)magnetic
D)None of the choices are correct.

Question 22

The swelling of a food-containing can is frequently due to the production of ___________ by spoilage microbes.

A)oxygen gas
B)nitrogen gas
C)carbon dioxide gas
D)All of the choices are correct.

Question 23

The conventional low-temperature holding procedure used in the pasteurization of milk involves holding the milk at 62.8^oC for __________ minutes.

A)5
B)15
C)30
D)60

Question 24

Which of the following is true about molecular methods of microorganism detection in foods?

A)They can be used to detect the presence of a single specific pathogen.
B)They can be used to detect viruses that are not easily cultured.
C)They can be used to detect slow-growing pathogens.
D)All of the choices are correct.

Question 25

The process of racking,used in the production of wines,involves

A)depressurizing bottles.
B)addition of sulfites.
C)addition of carbon dioxide.
D)removal of sediments.

Question 26

Food-borne pathogens are most commonly identified by

A)polymerase chain reaction (PCR).
B)standard culture techniques.
C)pulsed-field gel electrophoresis.
D)None of the choices are correct.

Question 27

If food-borne disease transmission requires ingestion of the pathogen,followed by growth of the organism,and release of toxins in the intestine it is referred to as a food-borne __________.

Question 28

Staphylococcus aureus,once it grows in a food,produces toxins that are not usually inactivated by heating.

Question 29

Clostridium botulinum and Bacillus cereus are important disease-causing microorganisms of food which cause _________.

A)infections
B)intoxications
C)cancers
D)birth defects

Question 30

A major organism considered to cause food-borne infection is

A)Salmonella.
B)Staphylococcus.
C)Pseudomonas.
D)Bacillus.

Question 31

A major fungal genus that produces aflatoxin is

A)Rhizopus.
B)Aspergillus.
C)Claviceps.
D)Penicillium.

Question 32

Aflatoxins are planar,ringed compounds that interact with DNA by ___________ and cause frameshift mutations.

A)substitution
B)rearrangement
C)deletion
D)intercalation

Question 33

If food-borne disease transmission does not require growth of the microorganism after ingestion because the toxic substances are already present in the food as a result of previous growth,then it is referred to as a food-borne __________.

Question 34

The largest meat recall in U.S.history was prompted by the discovery of contamination by

A)Listeria monocytogenes.
B)Clostridium botulinum.
C)Escherichia coli.
D)Pseudomonas aeruginosa.

Question 35

To control microbial growth in a food,one can decrease water availability by the addition of ________.

A)sugar or salt
B)gelatin
C)agar
D)formaldehyde

Question 36

The process of beer lagering involves _________.

A)carbonation
B)aging
C)distillation
D)None of the choices are correct.

Question 37

The polymerase chain reaction (PCR)can detect as few as 10 toxin-producing Escherichia coli in a population of 100,000 microorganisms isolated from soft cheese samples.

Question 38

A microorganism that has been used in the production of sour mash whiskey is _________.

A)Leuconostoc mesenteroides
B)Lactobacillus delbrueckii
C)Lactococcus lactis
D)Saccharomyces cerevisiae

Question 39

The production of natural carbon dioxide by yeasts after a wine is bottled results in ________.

A)sweet wine
B)dry wine
C)champagne
D)brandy

Question 40

Pulsed-field gel electrophoresis can be used to link a particular pathogen associated with disease outbreaks in a specific food source.

Question 41

Bread products can be spoiled by the growth of Bacillus species that produce _________.

A)gassy doughs
B)nonrising breads
C)ropiness
D)sourdough bread

Question 42

Streptococcus thermophilus and Lactobacillus bulgaricus contribute to the flavor of yogurt by producing diacetyl during the fermentation of lactose.

Question 43

Which of the following is most often used as a starter culture for the production of cheese?

A)Aspergillus species
B)Lactobacillus species
C)Rennet
D)Saccharomyces species

Question 44

Sequential growth of microorganisms in which the growth of one organism produces environmental conditions suitable for the subsequent growth of another organism is called ____________.

Question 45

The holes in Swiss cheese are produced by the metabolic activities of which bacterial genus?

A)Streptococcus
B)Propionibacterium
C)Leuconostoc
D)Lactobacillus

Question 46

You may have noticed that the prepackaged deli meats you purchase in the refrigerated section of the grocery store seem to last longer than the same meats purchased freshly sliced from the deli counter.You are puzzled because the meats are identical and you expect the products at the deli to be fresher.What is the primary reason the prepackaged meats last longer?

A)The prepackaged meats are typically sprayed with bacteriophage to prevent the growth of Listeria monocytogenes,which typically causes spoilage.
B)The prepackaged meats are stored at a much colder temperature than the deli case.
C)The prepackaged meats are not handled by the deli workers.
D)The prepackaged meats have modified atmosphere packaging that has excluded oxygen gas,which would promote the growth of spoilage organisms.

Question 47

Preservation of fermented meat products is accomplished by

A)the lower pH.
B)pasteurization.
C)the lower water activity.
D)the lower pH and lower water activity.
E)All of these choices are correct.

Question 48

What is a possible negative consequence of using bacteriophage to control food-borne pathogens?

A)The bacteriophage will alter the flavor and texture of the food.
B)The target bacteria may evolve resistance to individual strains of bacteriophage.
C)The bacteriophage may infect humans,causing disease.
D)The bacteriophage are likely to drastically alter the normal gut flora.

Question 49

In breadmaking,yeast growth is usually carried out under ____________ conditions,which results in more carbon dioxide production and less alcohol accumulation.
or

Question 50

Your roommate made potato salad and then let it sit on the counter overnight,forgetting to refrigerate it.When she discovered it in the morning,she asked you whether you thought it would be safe to eat.How should you reply?

A)Yes,as long as she refrigerates it now,since the cold will kill the microorganisms.
B)Yes,as long as she refrigerates it now,since the cold will slow the growth of any contaminating microorganisms.
C)No,because refrigeration will not inactivate microbial toxins that may have been produced while the salad sat at room temperature.
D)Yes,as long as she refrigerates it now,because any toxins produced will be destroyed by refrigeration.
E)Yes,as long as she refrigerates it now,since the cold will stop microbial growth and inactivate toxins.

Question 51

Feeding chickens a strain of Bacillus subtilis leads to

A)lower carriage of the pathogenic
B)increased body weight and feed conversion.
C)a reduction in coliforms and Campylobacter in the processed carcasses.
D)increased body weight and feed conversion and a reduction in coliforms and Campylobacter in the processed carcasses.
E)All of the choices are correct.

Question 52

Which of the following microbial genera is used in the production of fermented dairy products?

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

Question 53

Which of the following determines whether or not a wine is considered to be dry?

A)The percentage of alcohol after fermentation
B)The amount of free sugar after fermentation
C)The amount of carbon dioxide after fermentation
D)The type of grape used as a starting material

Question 54

Mold-lactic fermentation results in a unique fermented milk consumed in Finland and called ________________.

Question 55

In all cases,it is necessary for disease-causing microorganisms to grow in a food to result in disease transmission to humans.

Question 56

When Lactobacillus acidophilus are sprayed on feed,the cattle that eat it appear to have markedly lower carriage of the pathogenic E.coli strain O157:H7.

Question 57

The science of wine production is called ________.

A)enology
B)rheology
C)horology
D)eurology

Question 58

Some fermented dairy products have been suggested to have beneficial effects,including a reduction in the incidence of colon cancer and the minimization of lactose intolerance.

Question 59

Mashing is a process involving _________.

A)carbonation
B)protein putrefaction
C)inoculation
D)carbohydrate hydrolysis

Question 60

Freezing food is an excellent preservation method because freezing readily kills most if not all microorganisms contaminating the food.

Question 61

Which of the following is a fermented meat product?

A)Hot dogs
B)Italian sausage
C)Country-cured hams
D)Beef jerky