Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

NU FS 363 - food microbiology > Microorganisms in food > Flashcards

Microorganisms in food Flashcards

You may prefer our related Brainscape-certified flashcards:
Gourmet Food flashcards Biology 101 flashcards
1
Q

how are strains of species classified in microbiology?

A

mainly based on their virulence
-types of toxins produced, type of disease they cause, how they spread disease or specific host sites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the cut off for bacterial taxonomy using DNA-DNA hybridization?

A

70% similarity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is average nuclei identity used for?

A

a method to determine bacterial taxonomy that involves genome sequencing to determine genetic relatedness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are marker genes?

A

a method for bacterial taxonomy that allow us to use conserved regions within gene sequence to map out bacterial diversity and similarities

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what percent of average nuclei identity do organisms with genomic similarity share?

A

> 95%
- If two bacteria have an ANI score above 95-96%, they are considered to belong to the same species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

when does a majority of contamination of foods occur?

A

during processing / handling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

True or False: naturally, most muscle tissue, eggs and milk are sterile

A

True with some exceptions
- most of the contamination occurs after processing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what 3 microorganisms are common in plants and soil?

A

Bacillus spp. Pseudomonas and Lactiplantibacillus plantarum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is a high nutrient surface?

A

spaces that are in contact with food

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are most bacteria associated with foods called? what do they do?

A

chemotrophs
-use organic compounds as a source to produce ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what nutritional requirements to chemotrophs have?

A

most are fastidious which means they have specific or demanding nutritional or environmental requirements in order to grow
- some can get by with water and few nutrients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are the nutrients required for the growth of bacteria?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what considerations must be made in regards to growth vs survival?

A

in some environments bact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why is it important to understand the microbial growth curve?

A

because the rate of growth determines:
-how fast a food will spoil / ferment
-whether pathogenic bacteria will grow and produce toxin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what do control mechanisms of microbial growth aim to do?

A

-accelerate growth in fermentations
-stop growth of pathogens
-slow growth of spoilage organisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

why do some pathogens need to be killed and not just have their growth stopped? what are examples of these pathogens?

A

they may have a very low infectious dose
- salmonella and campylobacter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is generation time?

A

the time required for a population of bacteria to DOUBLE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is the equation to calculate generation time?

A

the difference between time A/B x log of 2 divided by the difference of the log of # bacteria at point A/B

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

how do you calculate number of generations?

A

time / generation time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is the difference between gram positive and gram negative?

A

Gram-positive bacteria: Thick peptidoglycan layer, no outer membrane, purple Gram stain, susceptible to antibiotics targeting cell walls.

Gram-negative bacteria: Thin peptidoglycan layer, outer membrane with LPS, pink Gram stain, more resistant to many antibiotics due to their outer membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what colour will a gram positive stain be?

A

purple

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what colour will a gram negative stain be?

A

pink

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

why is gram strain important?

A

this gives taxonomists guidance for classification:
- outer membrane or not is the first step in classification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what effect does the presence of an outer membrane have on bacteria?

A

it increases resistance of bacteria to antibiotics, bile salts, bacteriocins as well as some preservatives and sanitation agents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is the difference between spore forming bacteria and vegetative bacteria?

A

spore forming: form inactive spores in harsh environments in order to survive
- makes them highly resistant to many factors that usually kill bacteria

vegetative: typically in active growing state- do not grow spores making them less resistant to changes in environments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what bacteria commonly form spores?

A

Bacillus spp. and Clostridium spp.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what are yeasts? how can they affect food spoilage?

A

Eukaryotes- considered quite safe but can lead to spoilage

-fermentation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what type of yeast is key for brewing and baking?

A

Saccharomyces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what are fungi / molds? how can they lead to spoilage?

A

filamentous, multicellular fungi known for their role in decomposition and food production
-Grow in wide range of environments - T, pH , aW and produce mycotoxins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is the most common type of fungi found on foods?

A

Septate hyphae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what are viruses and how are they important in food microbiology?

A

microscopic infectious agents that can only replicate inside the genetic material (cells) of a host organism

they are important because they cause diseases in plants, humans, animals and bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

why do viruses need to have a host in order to reproduce?

A

they don’t have metabolite and need the metabolism of the host cell to reproduce
-reproduction usually causes death of host cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

how are viruses transmitted?

A

through foods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

how do viruses replicate inside foods?

A

they don’t!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What would Hepatitis A and Norovirus be classified as?

A

Viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what host do bacteriophages affect?

A

bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what are parasites?

A

Eukaryotes that live on or inside a host, deriving nutrients at the host’s expense

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what are the 3 parasitic groups relevant to food?

A

Protozoa, flatworm and roundworms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

how do parasites replicate in food?

A

they don’t!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

what is a definitive host for parasites? what are the symptoms?

A

an animal in which an adult parasite carries out sexual cycle
-typically asymptomatic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what is a intermediate host for parasites? what are the symptoms?

A

an animal where larval or juvenile forms of a parasite develop
- associated with disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what is a incidental host for parasites? what are the symptoms?

A

the parasite is unable to develop on host
- able to cause disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what class of bacteria is Trichinella spiralis (trichinosis)? how is it controlled?

A

A parasite found in omnivores - rodents, humans, pigs and bears

-controlled by cooking meat
>65 degrees C or frozen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what are trophozoites?

A

the active, feeding, and growing stage of certain protozoan parasites
-can cause infection and have cysts that survive outside host

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

what are physical changes common in food spoilage?

A

drying, crystallization and flavour loss

45
Q

what are chemical changes of food spoilage of lipids?

A

rancidity
oxidative - peroxides (chemical)
hydrolytic - free fatty acids (microbial )

46
Q

what are chemical changes of food spoilage of proteins?

A

proteolysis (microbial)
-protein breakdown causing putrefaction (pungent odour production)

47
Q

what are chemical changes of food spoilage of carbs?

A

fermentation (microbial)
- causes organic acids to sour

48
Q

how does raw meat spoil under aerobic vs anaerobic conditions?

A

anaerobic - souring
aerobic - protein degradation (putrefaction)

49
Q

what can be observed when bread has spoiled?

A

mould growth and starch crystallization

50
Q

what can be observed when yogurt spoils?

A

acid production and growth of molds / yeast

51
Q

what is the definition of a foods durable life?

A

the amount of time an unopened food product when stored in appropriate conditions will retain its freshness and nutritional values

52
Q

when must a food have a best before date?

A

when its packaged at a place other than the retail store and has a durable life < 90 days

53
Q

if a food is packaged by the retailer and has a durable life < 90 days what label must it contain?

A

A “packaged on” date

54
Q

what are examples of foods that need an expiration date?

A

liquid diets, low energy prescription diets, meal replacements, nutritional supplements and instant formula

55
Q

what can be assumed about a product if it can be consumed >90 days?

A

it is shelf stable

56
Q

what do expiration dates indicate?

A

how long a food will maintain its nutritional value and freshness

57
Q

are BBD and expiration dates an indication of food safety?

A

no

58
Q

what ways are food infection possible?

A

bacteria/virus growth surviving in the food (few organisms)

bacteria after growth in food (many organisms)

59
Q

how is food intoxication possible?

A

intoxication by bacterial or fungal toxins

60
Q

how much cells is needed to produce toxin in bacterial vs fungal toxins?

A

bacterial - few to many
fungal - many

61
Q

what is a toxicoinfection?

A

illness caused by ingestion of food containing pathogens which produces toxin in GI tract

62
Q

what is classified as a food intoxication?

A

toxin produced in the food then the food is ingested and illness occurs

63
Q

what do Bacillus cereus,
Clostridium botulinum,
Staphylococcus aureus and
Mycotoxins have in common?

A

they cause food intoxications

64
Q

what is a food infection?

A

when an organism is consumed and it colonizes the GI tract causing illness

65
Q

how many cells of Salmonella enterica are needed to cause a food infection?

A

10

66
Q

how many cells of enterohemorrhagic E. coli are needed to cause a food infection?

A

10

67
Q

how many cells of Salmonella enterica are needed to cause a food infection?

A

10

68
Q

how many cells of enteropathogenic E. coli are needed to cause a food infection?

A

> 1 mil

69
Q

what does blowing of vaccuum packaged beef indicate?

A

high volumes of gas production from organisms in food

70
Q

is it common for organisms to release gas?

A

yes, in small quantities
-uncommon for them to produce sufficient enough quantities to blow package up

71
Q

what organism is commonly the cause of blown meat vaccuum packages?

A

Clostridia

72
Q

what macro in meat do organisms metabolize in order to produce gas an odour?

A

protein

-some carbohydrates
-fat doesn’t usually produce gas when metabolized

73
Q

what is a strict anaerobe?

A

organism that will grow in the abscence of oxygen

74
Q

what affect does heat shrinking have on clostridia when packaging meat?

A

heat shrinking meat packages can cause spores to acitivate

75
Q

what T microorganism is most likely to cause blow packages?

A

Psychrophophiles

76
Q

how does blown packaging occur if antimicrobial treatments are used in meat processing?

A

clostridia survives antimicrobial treatments

77
Q

what types of meat are at risk for blown packages?

A

Beef, lamb, pork, venison

78
Q

How does MAP blown pack soilage differ from meat blown packages? what type of macros would you expect to see in the package?

A

The lack of off odours and no change in eating quality
-the lack of protein source in the food will decrease the risk of off odours
- carb as main macro

79
Q

For MAP blown packages:

what environment would you expect for the food? What kind of bacteria would you expect to grow as a result of this?

A

1) low O2
2) High CO2

Lactic acid bacteria will grow and some may produce CO2 from carbs

80
Q

what kind of microorgansims can you expect to be present in MAP blown packages with low protein availibility? why?

A

Enterobacteriaceae and Lactic acid bacteria
- these organisms can survive with lack of oxygen and they prefer carbohydrate-rich environments

81
Q

what differneces might you see in the packages of products that have been blown by Enterobacteriaceae / LAB and Clostridia?

A

Packages blown by Clostridia are likely to produce more gas and cause more blowing than packages affected by LAB and enterobacteriaceae

82
Q

what is the cause of blown packages by LAB and enterobacteriaceae?

A

-Temperature abuse (over 4 degrees C)
-Moderate distention
-more common towards the end of storage

83
Q

what is a common natural habitat for clostridia?

A

soil

84
Q

how can corrective action be taken to prevent blown packages?

A

1) determine the source of organism
- animal itself
- processing facility
- sampling

2) determine control measures
- LAB is highly resistant to sanitizers used in processing facility
- monthly control strategies

85
Q

when is clostridia most likely to be transferred? why is this?

A

during slaughter
- this is because clostridia commonly comes from the animal itself

86
Q

what are solutions to bread spoilage?

A

1) buy fresh bread when it’s needed
2) Bake dense/acidic bread such as sourdough (LAB inhibits growth of other microbes)
3) Add lots of sugar and fat
4) Add propionate and emulsifiers

87
Q

what type of organism is resposible for the blue mold found on bread?

A

pennicilin

88
Q

why is wrapped bread more succeptible to spoiling?

A

the wrapping causes condensation which can result in mold formation

89
Q

what are control measures for bread storage?

A

1) preservatives
2) packaging bread under clean air
3) post-packaging heat treatment

90
Q

what does a direct microscopic count measure? what is the limitation of this?

A

the number of cells
- we can’t tell if cells are dead or living

90
Q

what is quantification of bacterial DNA? what is the limitation of this?

A

PCR amplification of 16S rRNA genes (measuring the amount of bacterial DNA present in a sample)
-everything, including mitochondria and chloroplasts are visible
- it is for the genus level only
- dead and living cells are counted

91
Q

what is a standard plate count measure? what is the assumption with this?

A

measure of the # of live cells
-1 cell = one colony

91
Q

what type of organisms spoil bread?

A

airborne conidiospores

92
Q

what type of food do you expect to have a high cell count vs low cell count?

A

fermented or fresh plant food- high cell count
canned, cooked or pasterurized - low cell count
pasteurized / heated and stored in the fridge - starts low then goes high

93
Q

how can cell count be used to determine spoilage?

A

It can’t, it is no indication of spoilage

94
Q

what type of bacteria will grow on:

standard agar plate?

A

most bacteria

95
Q

what type of bacteria will grow on:

Violet red bile agar?

A

mesophilic aerobic Gram-negatives

96
Q

what type of bacteria will grow on:

APT?

A

meat spoilage organisms

97
Q

what type of bacteria will grow on:

sourdough broth

A

sourdough lactobacilli

more acidic

98
Q

what type of bacteria will grow on:

Baird-parker agar?

A

staphylococcous spp.

99
Q

what type of bacteria will grow on:

Cetrimide agar?

A

Pseudomonas spp.

100
Q

what is the difference between rich and defined laboratory media?

A

rich - nutrient dense
defined- has antibiotics to exclude some organsism and select for others

101
Q

How many dilutions are needed for:

Fermented food or produce? why is this the case?

A

log 8-9 CFU/g
- more dilutions are needed due to their higher cell count

102
Q

How many dilutions are needed for:

Heated food? why is this the case?

A

log 2 or lower
- fewer dilutions are needed do to lower cell count

103
Q

How many dilutions are needed for:

MAP food (long-storage life food)

A

log 8-9 CFU/g

104
Q

Explain how to inculate a food plate using the pour method?

A

1) add 1mL of sample to a steril petri dish
2) add sterile agar solution and mix well
- agar must be cooled to not kill the bacteria

105
Q

Explain how to inculate a food plate using the pour method?

A

1) Spread plate- add 0.1 mL of the sample to a plate
2) spread sample evenly over the surface with a sterile glass spreader

106
Q

Explain how to dilute a solid sample for a food plate

https://youtu.be/yYWFX4IXc5Y?si=yrMUGw1DeISSSSVT

A

1) blend solid with diluent (10mL per g)
2) make dilutions
3) pour onto plate

107
Q

What is enrichment and why is it needed?

In regards to food plating

A

Enrichment is the use of a selective broth in order to select for growth of a specific type of organism
- this is needed because food pathogens typically have a low abundance so enrichment is needed
- helps to detect pathogens

NU FS 363 - food microbiology (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions