Microbiology- chapter 41

What are some examples of extrnsic factors?

- Temperature - packaging - humidity: extrinsic - atomosphere

What is nisin used for?

- a small amphilic peptide used as a food preservative

What are some examples of intrinsic factors?

- amount of carbohydrates: - presence of a rind - oxidation-reduction potential - water activity - pH - physical strcture

When food supplies, such as beef and pork, are gamma irradiated to kill pathogenic organisms, the food becomes temporarily radioactive. There is no harm to humans because the effects have worn off by the time the meat reaches grocery store shelves. (True of false)

False because gamma irradated food does not become radioactive

What list was nisin added to in 1988?

GRAS

What kind of bacteria does nisin attack?

Gram positive

Ready-to-eat meats are being preserved by spraying a preparation of ____________ on the product prior to packaging.

bacteriophages

How does nisin attack gram positive bacteria?

by binding to lipid II during peptidoglycan synthesis and forms pores in the plasma membrane.

the main environmental factors that affect microorganism growth include

chemical inhibitors, oxygen, pH, nutrients, moisture, and temperature

Foods can be spoiled by both intrinsic and extrinsic factors. Extrinsic factors can include things such as ________. pH nutrients storage temperature biological barriers (e.g., shells) water availability

storage temperature

What are bacteriocins?

proteins that kill closely related microbes by binding to specific sites on the target cell.

Various chemicals are used to preserve food and prevent microbial spoilage. If you wanted to prevent Clostridium botulinum spore germination in your sausage meat, it would be best to use ________.

sodium nitrite

at freezing temperatures or during refrigeration, most bacteria ____________

stop growing, but are not dead

Gamma irradiation is used on a variety of foods to extend their shelf life. Some of the characteristics of irradiation are ______. (Check all that apply.) - an effective way to sterilize food -the food becomes temporarily radioactive -the process must be used with moist foods -the food temperature increases during the process

- an effective way to sterilize food -the process must be used with moist foods

What is nisin produced by?

- nisinstrains of Lactococcus lacti

What are some characteristics of mesophiles?

- performed at 25-30 celcius - uses lactococcus lactis - process used to make sour cream - microbes make diacetyl

Canned food available for sale at grocery stores have been subjected to a commercial canning process. If you bought a can of peas from the local grocery store and found the peas to be spoiled, it could explained by ______. (Check all that apply.) - underprocessing during canning - spoilage before canning - the fact that many spoilage organisms survive the commercial canning process - the entrance of contaminated water through the can seams during cooling

- underprocessing during canning - spoilage before canning - the entrance of contaminated water through the can seams during cooling

What are some characteristics of thermophiles?

-performed at 45 celcius -microbes make diacetyl and acetylaldehyde - uses streptococcus salivarius subsp. thermophilus - uses lactobacillus delbrueckii - process used to make yogurt

Johnny buys a package of fresh-sliced ham from the deli and places it in his refrigerator. Unbeknownst to him, there are 10,000 E. coli cells on his ham. After three days under refrigeration, predict the number of E. coli cells that would be on his ham, using what you know about the effects of refrigeration on most microbes. 0 About 100 Slightly more than 10,000 About 1,000,000,000

Slightly more than 10,000

Identify the steps that might occur leading to a food intoxications by Clostridium botulinum.

Step 1: Bacterial endospores contaminate many different foods Step 2: Endospores survive inadequate canning processes/ Canned foods are anaerobic Step 3: Surviving endospores germinate grow; and produce toxin in canned foods Step 4: A person ingests the toxin-containing food_ Symptoms of botulism begin in 12-36 hours

What is the beer making process?

Step 1: Barley moistening and germination Step 2: drying and crushing Step 3: mashing Step 4: add hops Step 5: heat in brew kettle Step 6: add yeast Step 7: fermentation Step 8: storage (lagering) Step 9: packaging

What is the wine process?

Step 1: Grape pressing Step 2: Steralization; yeast addition Step 3: fermentation of must Step 4: setting vat Step 5: aging Step 6: bottling

Correctly identify the steps that can lead to food-borne illness by Salmonella/Campylobacter

Step 1: Incomplete cooking of poultry and fruits/ vegetables fails to kill pathogens Step 2: Live salmonella bacteria are ingested Step 3: The pathogen multiplies in the intestinal tract for 2-48 days Step 4: Diarrhea, abdominal pain, and nausea can result

Correctly identify the steps that can lead to food-borne illness by E. coli

Step 1: Incomplete cooking of raw poultry fails to kill pathogens Step 2: Live E.Coli bacteria are ingested Step 3: A shiga-like toxin is produced Step 4: Bloody diarrhea and hemolytic uremic syndrome can result

Identify the steps that might occur leading to a food intoxications by Staphylococcus aureus

Step 1: Other bacteria in the food are killed/inhibited by cooking/salty conditions Step 2: A food handler carries the pathogen in their nasal cavity and transfers it to the food via their hands Step 3: The pathogen produces an enterotoxin when the food is held at room temperature for several hours Step 4: A person ingests the toxin-containing food, resulting in staphylococcal enteritis in two to six hours

Your friend tells you that she is lactose intolerant, but can eat yogurt without developing the cramps and bloating that other dairy products trigger. Why is this the case?

The bacteria in yogurt ferment almost all of the lactose to lactate

Above 100°C (212°F) most bacteria _________.

are destroyed

With ideal environmental factors, the reproduction rate of many bacterial species is ________.

extremely rapid

What is salting

lowers water activity and inhibits microbial growth.

Is nisin toxic?

no

What do bacteriocins affect?

the plasma membrane integrity and function

What is the canning process

use of heat is the sterilization of closed anaerobic containers

What is pasteurization?

used in milk where slightly lower temperatures are applied yet still effective in killing potential pathogens.