Microbiology Chapter 16:Microbiology of food and water

Which one of the following is an extrinsic factor that affects that rate of food spoilage?

a) The storage temperature

b) The pH of the food

c) The skin on a fruit

d) The water content of the food

e) The nutrient content of the food

a) The storage temperature

Which one of the following foods would have the highest water activity?

a) Almonds

b) Honey

c) Dried Beans

d) Apple

e) Rice

d) Apple

Evidence of microbial food spoilage requires the presence of at least _________ microbes per gram.

a) 100

b) 1000

c) 10,000

d 100,000

e) 1,000,000

e) 1,000,000

Lyophilization is

a) the acidification of food for long term storage.

b) a type of canning technique.

c) sun-dried food.

d) freeze-drying of food.

e) salting of food for storage.

d) freeze-drying of food.

When you add salt to meat for preservation you are

a) increasing the water activity of the meat.

b) decreasing the water activity of the meat.

c) increasing the pH of the meat.

d) decreasing the pH of the meat.

e) decreasing the nutrient content of the meat.

b) decreasing the water activity of the meat.

The most common food preservation method used in US households is

a) canning.

b) curing meat.

c) refrigeration.

d) heating.

e) freeze-drying.

c) refrigeration.

Canning is a technique used in food preservation. The food to be canned is heated to boiling for an hour

a) in the presence of high salt.

b) under acidic conditions.

c) with a preservative added for long term storage.

d) under pressure of 10 - 15 psi.

e) and immediately chilled after boiling.

d) under pressure of 10 - 15 psi.

The most common disease associated with improperly canned food is

a) botulism.

b) tetanus.

c) gastroenteritis.

d) colitis.

e) stomach ulcer.

a) botulism.

Pasteurization is a method of preservation that involves heating the liquid to _______ °C for 30 min.

a) 45

b) 63

c) 85

d) 100

e) 121

b) 63

Most milk sold in stores today has an extended shelf life primarily because of

a) canning techniques.

b) refrigeration.

c) Tyndallization.

d) high temperature short term pasteurization.

e) the addition of chemical preservatives.

d) high temperature short term pasteurization.

Pickling is a preservation method that uses __________ to help preserve the food.

a) alcohol

b) heat

c) acid

d) freezing

e) spices

c) acid

Small protein molecules produced by a microorganism that adversely affect a closely related microorganism are called

a) siderophores.

b) bacteriocins.

c) lysozymes.

d) beta-blockers.

e) proteases.

b) bacteriocins.

Which of the following type of radiation may be used to sterilize food?

a) Long range ultra-violet

b) Visible light

c) Radio waves

d) Ionizing

e) Infrared

d) Ionizing

Vacuum packaging inhibits the growth of microbes that

a) are obligate anaerobes.

b) rely on fermentation for energy metabolism.

c) are aerotolerant anaerobes.

d) rely on aerobic respiration for growth.

e) are chemolithotrophs.

d) rely on aerobic respiration for growth.

All of the following microbes play an important role in the production of fermented milk products except for

a) Lactobacillus.

b) Leuconostoc.

c) Lactococcus.

d) Saccharomyces.

e) Streptococcus.

d) Saccharomyces.

Which one of the following foods is not a fermented milk product?

a) Swiss cheese

b) Kefir

c) Butter

d) Butter milk

e) Yogurt

c) Butter

This microorganism is often used to make fermented semi-dry sausages and salami.

a) Leuconostoc

b) Pediococcus

c) Saccharomyces

d) Aspergillus

e) Lactobacillus

b) Pediococcus

What bacterium is used in the production of Swiss cheese to give it its characteristic flavor and also the holes from carbon dioxide production?

a) Pediococcus

b) Leuconostoc

c) Propionibacterium

d) Clostridium

e) Pseudomonas

c) Propionibacterium

The fungus Penicillium is used in the production of

a) blue cheese.

b) cheddar cheese.

c) limburger cheese.

d) American cheese.

e) Colby cheese.

a) blue cheese

The protease rennin is used in the production of

a) butter.

b) yogurt.

c) kefir.

d) cheese.

e) ice cream

d) cheese

Fermented soybean products, like miso and tempeh, are produced using

a) lactic acid bacteria.

b) molds.

c) propionate bacteria.

d) acetic acid bacteria.

e) Saccharomyces.

b) molds.

Vinegar production occurs through the oxidation of ethanol by

a) lactic acid bacteria.

b) the yeast Saccharomyces.

c) various molds.

d) sulfate-reducing bacteria.

d) acetic acid bacteria.

d) acetic acid bacteria.

Staphylococcus aureus causes foodborne illness through

a) the production of an enterotoxin that contaminates prepared foods.

b) a break in the skin during food preparation.

c) the ingestion of the microbe which grows in the large intestine to produce symptoms.

d) the production of an exotoxin after ingestion of the microbe.

e) the consumption of undercooked meat.

a) the production of an enterotoxin that contaminates prepared foods.

Which microbe listed below causes foodborne intoxication?

a) Shigella

b) Salmonella

c) Staphylococcus

d) Campylobacter

e) Vibrio

b) Salmonella

An example of an organism that causes a foodborne infection is

a) Staphylococcus aureus.

b) Campylobacter jejuni.

c) Clostridium perfringens.

d) Clostridium botulinum.

e) Bacillus cereus.

b) Campylobacter jejuni.

All of the following are goals of wastewater treatment except

a) reduction of total organic content (TOC).

b) removal of harmful pathogens.

c) enhancement of the taste of water.

d) removal of nitrogen.

e) removal of phosphorus.

c) enhancement of the taste of water.

The main goal of the primary treatment phase of wastewater treatment is the

a) reduction of total organic content (TOC).

b) removal of pathogenic microbes.

c) reduction of nitrogen.

d) removal of particulate matter.

e) removal of toxic chemicals.

d) removal of particulate matter.

Which of the following methods use microbial biofilms for secondary phase of wastewater treatment?

a) trickling filter

b) activated sludge

c) anaerobic digester

d) nitrification tank

e) oxidation pond

a) trickling filter

The activated sludge method of wastewater treatment uses

a) a microbial biofilm for organic carbon reduction.

b) an inoculum from the previous activated sludge treatment.

c) chemolithotrophic bacteria for carbon reduction.

d) special chemicals for the removal of organic pollutants.

e) large screens to filter out particulate matter.

b) an inoculum from the previous activated sludge treatment.

The ________________ is a measure of the amount of oxygen required for the microbial oxidation of organic compounds in a water source.

a) chemical oxygen demand

b) biological oxygen demand

c) respiration rate

d) carbon dioxide production

e) cell yield

b) biological oxygen demand

The release of high levels of nitrogen and phosphorus into streams after wastewater treatment will result in

a) the production of high quality water for plant irrigation.

b) water that tastes bad.

c) eutrophication of the stream.

d) increased nutrients for the fish in the stream.

e) increase in oxygen levels in the stream.

c) eutrophication of the stream.

The gas __________ is frequently recovered from anaerobic digesters at a waste treatment plant.

a) methane

b) carbon dioxide

c) hydrogen

d) nitrogen

e) argon

a) methane

Anaerobic digesters at wastewater treatment plants are used to

a) reduce nitrogen and phosphorus in wastewater.

b) remove toxic organic pollutants.

c) remove potential pathogens.

d) treat wastewater effluent.

e) treat sludge and particulates collected during waste treatment.

e) treat sludge and particulates collected during waste treatment

Ozonation is a wastewater treatment used to

a) remove organic pollutants.

b) disinfect wastewater.

c) reduce nitrogen levels in the water.

d) remove heavy metals that may be present in wastewater.

e) remove phosphorus from wastewater.

b) disinfect wastewater.

All of the following are processes that may be used in the treatment of drinking water except

a) filtration.

b) activated sludge digestion.

c) flocculation.

d) chlorination.

e) sedimentation.

b) activated sludge digestion.

The pH of an orange is an intrinsic factor that affects the shelf-life of the fruit.

true

Foods with high water activity will usually spoil faster than foods with a low water activity.

true

The addition of salt to certain food for preservation has been used for hundreds of years. Salt helps to preserve food by lowering the water activity.

true

Canning is the most prominent method of food preservation in industrialized countries today.

false

Pasteurization is a process of food preservation that results in sterilization.

false

Chemical food preservatives like sodium benzoate, acetic acid, and propionate are all weak acids.

true

Irradiation of food by gamma radiation will make the food radioactive.

false

Many bacteria that are used for the production of various fermented milk products belong to the lactic acid bacteria group.

true

A person eats some leftover potato salad from a picnic and becomes ill within three hours. This type of food poisoning is referred to as a "food-infection".

false

One of the main reasons for wastewater treatment is to reduce the BOD.

true

Food storage temperature is an ____________ factor that affects the rate at which a food will spoil.

extrinsic

The amount of water in a food that is available to microorganisms is referred to as ________ ______.

water activity

Small proteins produced by some bacterial to inhibit the growth of closely related bacteria are called __________________.

bacteriocins

The bacterium that gives Swiss cheese its characteristic flavor and holes is in the genus ____________.

Propionibacterium

Vinegar is made by bacteria from one of two genera, either Gluconobacter or ________________.

Acetobacter

Describe the process of vinegar production by the trickle method. Name the two genera of bacteria involved. Why do they produce vinegar?

Vinegar is produced by acetic acid bacteria, Gluconobacter or Acetobacter, through the oxidation of ethanol to acetic acid for energy production. Several different methods are used for the production of vinegar and all involve the exposure of the bacteria to ethanol under aerobic conditions. The trickle method uses wood twigs or shavings covered by a biofilm of one of the acetic acid bacteria. Ethanol containing liquid is trickled through a column packed with the biofilm-containing wood fragments. As the liquid trickles through the biofilm, the ethanol is oxidized to acetic acid (vinegar) by the microbes. The oxidation of ethanol to acetic acid provides the microbe with a source of energy for growth.

Compare and contrast a food-borne infection to intoxication.

A food-borne intoxication is the ingestion of a toxin or enterotoxin that is produced by a microorganism growing on the food source. The microbe itself does not cause any harm after ingestion, but the toxin it has previously produced will cause the specific symptoms observed. A person will become ill within a few hours after ingestion of the enterotoxin because the toxin has a very rapid affect on the GI tract. Many enterotoxins are heat stable and food that has been contaminated by an enterotoxin will be unsafe to eat, even after the food is reheated. A food-borne infection is the ingestion of a microbial pathogen that will cause a GI or systemic infection. Symptoms are usually observed about 3 to 4 days after consumption of the contaminated food because the microbe needs to grow in the intestinal tract. Proper cooking of food will kill the pathogen and prevent an infection.

Describe the activated sludge method for treatment of wastewater effluent. What is the major goal of this method?

The activated sludge method is a very efficient and fast method for reducing the biological oxygen demand (BOD) for the treatment of wastewater effluent. The method uses sludge from a previous treatment as an inoculum for the treatment of incoming effluent. The microbes in the sludge are still very biologically active and do not require any acclimation time. After the sludge is combined with the effluent, it is mixed with vigorous aeration by pure oxygen to enhance the aerobic degradation of the readily metabolizable organics present in the effluent. After treatment the mixture is transferred to a settling tank. Some of the sludge that settles out is then used as an inoculum for the incoming effluent.