Chapter 33.6 and 33.14: Microbiology of Food

food spoilage

any change in appearance, smell, or taste of a food that makes it unpalatable to the consumer

can food spoilage be safe to eat

yes it can be safe to eat due to the absence of pathogens

susceptibility to microbial spoilage - 2 factor

extrinsic and intrinsic factors

intrinsic factors

food composition (chemical) and structure (physical)

extrinsic factors

environmental influence (how food was handled)

3 categories of food

perishable, semi-perishable, and nonperishable

perishable food description

a lot of water content

semi-persishable food description

will eventually perish- medium water content

nonperishable food description

can sit out for a while- no water almost content

are spoilage organisms edible

yes food with spoilage organisms can still be eaten

carbohydrates (food composition and spoilage)

mold predominates, degrades food by hydrolysis, little odor, and ergotism

why does mold predominate in carbohydrates

spoilage organisms do not have enough water

ergotism

disease caused by Claviceps purpurea toxins

protein or fats (food composition and spoilage)

bacterial growth predominates, putrefaction

putrefaction

anaerobic breakdown of proteins which causing foul-smelling amine compounds

intrinsic factors types

pH, presence/availability of water, oxidation-reduction potential, physical structure, and antimicrobial substances

pH (intrinsic factor)

low pH favors yeast and mold

presence and availability of water (intrinsic factors)

lower water activity inhibits microbial growth

oxidation-reduction potential (intrinsic factor)

lower redox (less oxygen) favors growth of anaerobic bacteria

physical structure (intrinsic factor)

grinding and mixing promotes microbial growth

antimicrobial substances (intrinsic factor)

coumarins, lysozyme, allicin

extrinsic factors types

temperature, relative humidity, atmosphere

temperature (extrinsic factor)

lower temperatures slow microbial growth

relative humidity (extrinsic factor)

higher levels promote microbial growth

atmosphere (extrinsic factor)

oxygen promotes growth

modified atmosphere packaging (MAP)

use of shrink wrap or vacuum seal

food preservation 3 types

removal of microbes through filtration

low temperature food preservation

refrigeration and freezing

refridgeration temperature

4 C

freezing temperature

-20 C

high temperature food preservation

cooking and holding at high temperature (buffets), canning, and pasteurization

danger zone

5-60 C

high temperature: canning

food heated to 115C for 25-100 minutes to kill spoilage microbes

spoilage of commercially canned foods is

rare

pasteurization

kills pathogens and substantially reduces number of spoilage organisms

shorter pasteurization times results in

improved flavor

LTH

low temperature holding

low temperature holding description

63 C for 30 min

HTST

high temperature short time

high temperature short time description

72 C for 15 seconds

UHT

ultrahigh-temperature

ultrahigh temperature description

138C for 1-3 seconds

which of these pasteurization processes is considered sterile

UHT

reduction in water availability

dehydration and adding solutes

chemical-based preservation

GRAS

GRAS

chemical agents “generally recognized as safe”

radappertization

use of ionizing radiation (gamma radiation) to extend shelf life of foods

penetrating power of radappertization

excellent penetrating power that can sterilize some food

#1 foodborne disease

norovirus

foodborne disease cases

48 million per year

foodborne disease transmission

fecal-oral route + fomites

food intoxication

ingestion of preformed microbial toxins in food

growth of pathogen food intoxication

growth not required

food infection

infection resulting from the ingestion of pathogens in food

growth of pathogen food infection

ingestion followed by colonization and growth in host (may still produce toxins)

staphylococcus aureus bacteria

gram positive cocci

oxygen requirement S. aureus

facultative aerobe

salinity/water activity environment of S. aureus

can thrive in high-salt and low Aw habitats

sources of S. aureus

human nasal cavity, skin, and skin sores

toxin produced from S. aureus

enterotoxin producer

enterotoxins

heat stable toxin that targets the intestines/guts and is resistant to digestive protease and stomach acid

food that have S. aureus

poultry, egg salads, puddings, vegetables

which has faster onset of symptoms: food intoxication vs food infection

food intoxication has rapid onset

is staphylococcal food intoxication or infection

food intoxication with rapid onset

symptoms of staphylococcal food intoxication

nausea, explosive vomiting, no fever

duration of staphylococcus food intoxication

1-2 days

clostridium botulinum bacteria

gram positive bacilli, spore former

oxygen requirement of clostridium botulinum

strict anaerobe

sources of C. botulinum

soil/water and often seen in wounds and infants

toxin produced from C. botulinum

heat labile proteinaceous neurotoxin

neurotoxin

infects the nervous system and brain

neurotoxin is also called

exotoxin

what environment is the neurotoxin best produced

high protein and low acid foods

heat interference of neurotoxin

destroyed by high heat

foods with C. botulinum

corn and beans

is botulism food intoxication or food infection

food intoxication

botulism may have what contaminate raw foods before harvest or slaughter

endospores

symptoms of botulism

heart paralysis and difficulty swallowing/breathing

duration of botulism

1-10 days

botulism mortality

3-5%

botulism treatment

antitoxin

is clostridium perfrigens food intoxication or food infection

food infection with slow onset

clostridium perfringens in food

spores activated by cooking and germinate under anoxic conditions (piled food)

clostridium perfringens toxin

enterotoxin

clostridium perfringens vegetative cells

killed by cooking and extended by low temperatures

onset of clostridium perfringens

7-15 hours

what symptoms are rare of c. perfringens

vomiting and fever are rare

duration of c. perfringens

12-24 hours

what food condition is C. perfringens mainly found

food in bulk

salmonella enterica bacteria

gram negative bacillus

oxygen requirement of salmonella enterica

facultative aerobe

source of salmonella enterica

sewage (GI of birds)

salmonella enterica foods

poultry (eggs), pork, fruits

is salmonellosis food intoxication or food infection

food infection

salmonellosis cells multiple and colonize in

the small and large intestine, then invade and grow in phagocytic cells

salmonellosis virulence factors

endotoxins, enterotoxins, and cytotoxins

endotoxins

found in gram negative from lipid A of outermembrane

salmonellosis is spread from

fecal contamination of food via food handler or livestock

onset of salmonellosis

8-48 hours

symptoms of salmonellosis

headache, vomiting, fever