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BIOL 3330 - microbio 2 > food microbiology: spoilage, preservation, pathogens, fermentation, etc > Flashcards

food microbiology: spoilage, preservation, pathogens, fermentation, etc Flashcards

1
Q

what is spoiled food

A

food that supports the growth of microorganisms

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2
Q

T or F: spoiled food is unsafe

A

false; not necessarily. It is undesirable however

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3
Q

define perishable foods

A

foods that spoil quickly

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4
Q

what characteristics do perishable foods often have

A

nutrient rich + moist

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5
Q

define semi-perishable foods

A

not likely to spoil quickly

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6
Q

define non-perishable foods

A

can be stored indefinitely without spoiling

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7
Q

list some characteristics of non-perishable foods

A

nutritionally poor, dry, fermented or preserved

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8
Q

list the 2 types of factors that control whether or not microbes will grow in food

A

intrinsic and extrinsic factors

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9
Q

define intrinsic factors

A

relate to the characteristics of the food itself

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10
Q

define extrinsic factors

A

relate to how the food is handled, processed, or stored

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11
Q

list 5 intrinsic factors of food

A

food composition, water availability, pH, physical structure, presence of naturally occurring antimicrobial substances

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12
Q

describe food composition as an intrinsic factor in regards to food spoilage

A

nutritionally rich vs poor foods will determine spoilage

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13
Q

what organism will carbs be spoiled by

A

fungi

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14
Q

what organism with meats/butter be spoiled by

A

bacteria

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15
Q

describe water availability as an intrinsic factor in regards to food spoilage

A

foods with low water activity do not support microbial growth

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16
Q

most spoilage bact3ria require an Aw (water activity) of ____

A

0.91

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17
Q

describe pH as an intrinsic factor in regards to food spoilage

A

microbes have preferred pH growth ranges

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18
Q

what is the preferred pH range of an acidophile

A

0.0-5.5

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19
Q

what is the preferred pH range of an neutrophile

A

5.5-8.0

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20
Q

are fungi acidophiles or neutrophiles

A

acidophiles

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21
Q

are bacteria acidophiles or neutrophiles

A

neutrophiles

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22
Q

describe physical structure of food as an intrinsic factor in regards to food spoilage

A

the presence of an outer covering will decrease the chance of spoilage (ie avocado or egg). Ground meat has more surface area = spoils faster

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23
Q

describe the presence of naturally occurring antimicrobial compounds as an intrinsic factor in regards to food spoilage

A

eggs contain lysozyme which cleaves NAM-NAG bonds of a peptidoglycan backbone (degrades cell wall)

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24
Q

what are two of the most antimicrobial spices

A

sage and rosemary

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25
Q

list 4 extrinsic factors that are involved in food spoilage

A

temperature, storage packing, processing, amount of preservatives

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26
Q

describe temperature as an extrinsic factor in regards to food spoilage

A

storage temp influences microbial growth. Temps of 4C or less inhibits the growth of most bacteria

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27
Q

describe storage packing as an extrinsic factor in regards to food spoilage

A

are foods exposed or wrapped?

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28
Q

describe processing of food as an extrinsic factor in regards to food spoilage

A

foods that are less processed have a greater risk of spoilage

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29
Q

describe amount of preservatives as an extrinsic factor in regards to food spoilage

A

presence of added preservatives will decrease the risk of spoilage

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30
Q

what is the goal of food preservation

A

to remove or reduce the population of spoilage and disease causing microbes while maintaining food quality

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31
Q

list the phases on the bacterial growth curve

A

lag, log/exponential, stationary, death, long-term stationary

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32
Q

during which phase on the bacterial growth curve is food spoilage typically observed? why?

A

the end of the exponential phase bc they’re the most metabolically active here

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33
Q

list 4 different types of spoilage

A

souring, bittering, rancidity, putrefaction

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34
Q

what is souring

A

acid fermentation

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35
Q

what is bittering

A

alkaline fermentation

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36
Q

what is randicity

A

the oxidation of fats

37
Q

what is putrefaction

A

breakdown of proteins into amino acids

38
Q

how many microbes per ml or g of product are required for food spoilage to be evident

A

above 10^6

39
Q

which phase of the growth curve is most critical when it comes to food preservation? why?

A

the lag phase + log phase; we want a method that extends the lag phase and delays entry into the log phase

40
Q

food processing: describe filtration + it’s uses

A

filters out bacteria/microbes. Used for water, wine, beer juices, soft drinks

41
Q

food processing: describe low temp + it’s uses

A

slows the growth of existing microbes but doesn’t decrease the population

42
Q

T or F: low temps kill microbes

A

false; it only slows the growth but doesn’t decrease the population

43
Q

T or F: low temps can slow the growth of all microbes

A

false; psychrotrophs can withstand low temps

44
Q

food processing: describe freezing temp + it’s uses

A

decreases water activity, inhibits bacterial growth

45
Q

disadvantages of freezing temp in food processing?

A

can’t do on all food types, freezer burn may occur, doesn’t kill bacteria

46
Q

food processing: describe high temp+ it’s uses

A

cooking food will kill most/all microbes that may be present

47
Q

describe why high temps as food processing don’t always work

A

exotoxins are heat stable, so the method doesn’t always inhibit everything

48
Q

food processing: describe canning + it’s uses

A

another high temp method. Food is heated + high pressure

49
Q

describe what conditions are used in canning

A

100C for 20-100 min at 10-15 psi

50
Q

advantage of canning

A

everything is killed

51
Q

disadvantage of canning

A

there is loss of some food value: some vitamins are heat sensitive. Also food texture changes may occur

52
Q

food processing: describe pasteurization + it’s uses

A

another high temp method. Food is heated to a temp that eliminated disease causing microbes and reduces the number of spoilage microbes

53
Q

T or F: pasteurization significantly changes the nutritional quality of milk

A

false; it is not a significant change

54
Q

food processing: how would someone reduce the water activity of food

A

by drying, adding solutes, or increasing sugar

55
Q

food processing: describe freeze drying/lyophilization + it’s uses

A

product is frozen and then dried under vacuum, then stored in an airtight package

56
Q

describe how changing the acidity of food helps to preserve it

A

most spoilage occurs at pH of 6-8

57
Q

changing acidity of food to preserve it: what pH is achieved during pickling

A

4.6

58
Q

changing acidity of food to preserve it: how do we change the pH of meat

A

meat carcasses are sprayed with an organic acid solution

59
Q

list some chemical preservatives that can be added to food

A

benzoic acid, parabens, sulfites, ethylene

60
Q

food processing: describe irradiation

A

uses gamma (ionizing) radiation. It has great penetrating power and gets rid of all microves

61
Q

what are bacteriocins

A

small proteins naturally produced by some bacteria that can exert a negative effect on a closely related bacteria

62
Q

food processing: what are bacteriocins often added to

A

ready to eat meats, liquid whole eggs, concentrated fruit juice

63
Q

food processing: describe the use of a controlled atmosphere+ it’s uses

A

apples are stored in a high CO2 environment. high CO2 gets rid of ethylene and ethylene ripens fruit. This keeps fruit fresh for longer

64
Q

food processing: describe the use of modified atmosphere packaging + it’s uses

A

use of shrink-wrap vacuum technology to remove the oxygen, or use impermeable plastic pouches which are evacuated and sealed

65
Q

T or F: lots of spices have antimicrobial compounds

A

true

66
Q

list the two types of food-related diseases

A

food infection and food intoxication

67
Q

how are food-borne infections caused

A

by ingesting the microbe, and then it grows within the host and causes disease through invasion and/or toxin release (exotoxins)

68
Q

how is food intoxication caused

A

the illness is caused by ingestion of exotoxins that are present in the food

69
Q

which has faster presentation of symptoms: food infection or toxication? why

A

intoxication has quicker symptoms because the toxin is ingested, not the microbe. Growth of the microbe is not required

70
Q

list some symptoms of food poisoning

A

nausea, diarrhea, vomiting, fever, fatigue, muscle cramps

71
Q

when do food poisoning symptoms occur

A

2-48 hours after ingestion

72
Q

list 5 foodborne pathogens

A

bacteria, fungi, viruses, algae, protozoa

73
Q

give an example of a fungal derived toxin

A

aflatoxin

74
Q

what is aflatoxin caused by

A

growth in moist grains and nuts

75
Q

list 2 algae that produce toxins

A

dinoflagellates and diatoms

76
Q

describe a dinoflagellate’s toxin effects/how it’s produced

A

warm conditions –> bloom that results in the formation of a red tide. Shellfish eat the algae and pick up the toxin. Humans eat the shellfish and get paralytic shellfish poisoning

77
Q

describe a diatom’s toxin effect/how it works

A

called domoic acid. It can contaminate shellfish and humans can get amnesic shellfish poisoning. It can also accumulate in anchovies or lead to death in marine animals

78
Q

give an example of a protozoa that produces toxins + what it causes

A

toxoplasma gondii causes toxoplasmosis

79
Q

cause of toxoplasmosis?

A

caused by eating raw/undercooked meat from contaminated animals, or by ingesting food/water that has been contaminated with an infected cat’s feces

80
Q

symptoms of toxoplasmosis

A

swollen lymph nodes in neck, aches and pains, headache, fever

81
Q

list 2 ways to control food-borne pathogens

A

biocontrol agents or predatory bacteria

82
Q

describe how biocontrol agents can be used to control food-borne pathogens

A

its the process of using “living” organisms to combat the growth of pathogens in food (ie bacteriophages)

83
Q

describe how predatory bacteria can be used to control food-borne pathogens

A

ie B bacteriovorus preys on other gram neg bacteria. they’re multi-drug resistant, prey on biofilms

84
Q

how does food fermentation work

A

microbes are used to create foods that have dif textures, tastes, aromas compared to the natural food. Or they can preserve or stabilize the food, or change the product so after ingestion a change in mental state is noticed (ie beer) The changes occur due to the metabolic end-products of the microbes

85
Q

list 3 major fermentations

A

lactic acid, propionic acid, alcoholic fermentation

86
Q

describe sauerkraut production

A

shredded cabbage into an airtight container. Add salt to inhibit the growth of microbes on the leaf surfaces. Promotes growth of leuconostoc spp and lactobacillus spp. pH drops and lactobacillus dominates over the other

87
Q

describe yogurt production

A

whole milk is centrifuged to get rid of some fat. Milk is pasteurized, add mixed starter culture, ferment, may add probiotics or fruits/flavouring

88
Q

describe chocolate production

A

seeds and pulp of cacao pod are removed. Pod is covered with banana leaves. fermentation occurs for 5-7 days and yeasts/bacteria will aid in this. yeasts grow first and they ferment the sugars and produce alcohol. Temp/alcohol will increase so bacteria now dominate. After fermentation the beans are air dried

89
Q

define probiotic

A

live organism which when administered in adequate amounts confer a health benefit on the host

BIOL 3330 - microbio 2 (8 decks)

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