food microbiology: spoilage, preservation, pathogens, fermentation, etc Flashcards
(89 cards)
1
Q
what is spoiled food
A
food that supports the growth of microorganisms
2
Q
T or F: spoiled food is unsafe
A
false; not necessarily. It is undesirable however
3
Q
define perishable foods
A
foods that spoil quickly
4
Q
what characteristics do perishable foods often have
A
nutrient rich + moist
5
Q
define semi-perishable foods
A
not likely to spoil quickly
6
Q
define non-perishable foods
A
can be stored indefinitely without spoiling
7
Q
list some characteristics of non-perishable foods
A
nutritionally poor, dry, fermented or preserved
8
Q
list the 2 types of factors that control whether or not microbes will grow in food
A
intrinsic and extrinsic factors
9
Q
define intrinsic factors
A
relate to the characteristics of the food itself
10
Q
define extrinsic factors
A
relate to how the food is handled, processed, or stored
11
Q
list 5 intrinsic factors of food
A
food composition, water availability, pH, physical structure, presence of naturally occurring antimicrobial substances
12
Q
describe food composition as an intrinsic factor in regards to food spoilage
A
nutritionally rich vs poor foods will determine spoilage
13
Q
what organism will carbs be spoiled by
A
fungi
14
Q
what organism with meats/butter be spoiled by
A
bacteria
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
16
Q
most spoilage bact3ria require an Aw (water activity) of ____
A
0.91
17
Q
describe pH as an intrinsic factor in regards to food spoilage
A
microbes have preferred pH growth ranges
18
Q
what is the preferred pH range of an acidophile
A
0.0-5.5
19
Q
what is the preferred pH range of an neutrophile
A
5.5-8.0
20
Q
are fungi acidophiles or neutrophiles
A
acidophiles
21
Q
are bacteria acidophiles or neutrophiles
A
neutrophiles
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
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)
24
Q
what are two of the most antimicrobial spices
A
sage and rosemary
25
list 4 extrinsic factors that are involved in food spoilage
temperature, storage packing, processing, amount of preservatives
26
describe temperature as an extrinsic factor in regards to food spoilage
storage temp influences microbial growth. Temps of 4C or less inhibits the growth of most bacteria
27
describe storage packing as an extrinsic factor in regards to food spoilage
are foods exposed or wrapped?
28
describe processing of food as an extrinsic factor in regards to food spoilage
foods that are less processed have a greater risk of spoilage
29
describe amount of preservatives as an extrinsic factor in regards to food spoilage
presence of added preservatives will decrease the risk of spoilage
30
what is the goal of food preservation
to remove or reduce the population of spoilage and disease causing microbes while maintaining food quality
31
list the phases on the bacterial growth curve
lag, log/exponential, stationary, death, long-term stationary
32
during which phase on the bacterial growth curve is food spoilage typically observed? why?
the end of the exponential phase bc they're the most metabolically active here
33
list 4 different types of spoilage
souring, bittering, rancidity, putrefaction
34
what is souring
acid fermentation
35
what is bittering
alkaline fermentation
36
what is randicity
the oxidation of fats
37
what is putrefaction
breakdown of proteins into amino acids
38
how many microbes per ml or g of product are required for food spoilage to be evident
above 10^6
39
which phase of the growth curve is most critical when it comes to food preservation? why?
the lag phase + log phase; we want a method that extends the lag phase and delays entry into the log phase
40
food processing: describe filtration + it's uses
filters out bacteria/microbes. Used for water, wine, beer juices, soft drinks
41
food processing: describe low temp + it's uses
slows the growth of existing microbes but doesn't decrease the population
42
T or F: low temps kill microbes
false; it only slows the growth but doesn't decrease the population
43
T or F: low temps can slow the growth of all microbes
false; psychrotrophs can withstand low temps
44
food processing: describe freezing temp + it's uses
decreases water activity, inhibits bacterial growth
45
disadvantages of freezing temp in food processing?
can't do on all food types, freezer burn may occur, doesn't kill bacteria
46
food processing: describe high temp+ it's uses
cooking food will kill most/all microbes that may be present
47
describe why high temps as food processing don't always work
exotoxins are heat stable, so the method doesn't always inhibit everything
48
food processing: describe canning + it's uses
another high temp method. Food is heated + high pressure
49
describe what conditions are used in canning
100C for 20-100 min at 10-15 psi
50
advantage of canning
everything is killed
51
disadvantage of canning
there is loss of some food value: some vitamins are heat sensitive. Also food texture changes may occur
52
food processing: describe pasteurization + it's uses
another high temp method. Food is heated to a temp that eliminated disease causing microbes and reduces the number of spoilage microbes
53
T or F: pasteurization significantly changes the nutritional quality of milk
false; it is not a significant change
54
food processing: how would someone reduce the water activity of food
by drying, adding solutes, or increasing sugar
55
food processing: describe freeze drying/lyophilization + it's uses
product is frozen and then dried under vacuum, then stored in an airtight package
56
describe how changing the acidity of food helps to preserve it
most spoilage occurs at pH of 6-8
57
changing acidity of food to preserve it: what pH is achieved during pickling
4.6
58
changing acidity of food to preserve it: how do we change the pH of meat
meat carcasses are sprayed with an organic acid solution
59
list some chemical preservatives that can be added to food
benzoic acid, parabens, sulfites, ethylene
60
food processing: describe irradiation
uses gamma (ionizing) radiation. It has great penetrating power and gets rid of all microves
61
what are bacteriocins
small proteins naturally produced by some bacteria that can exert a negative effect on a closely related bacteria
62
food processing: what are bacteriocins often added to
ready to eat meats, liquid whole eggs, concentrated fruit juice
63
food processing: describe the use of a controlled atmosphere+ it's uses
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
food processing: describe the use of modified atmosphere packaging + it's uses
use of shrink-wrap vacuum technology to remove the oxygen, or use impermeable plastic pouches which are evacuated and sealed
65
T or F: lots of spices have antimicrobial compounds
true
66
list the two types of food-related diseases
food infection and food intoxication
67
how are food-borne infections caused
by ingesting the microbe, and then it grows within the host and causes disease through invasion and/or toxin release (exotoxins)
68
how is food intoxication caused
the illness is caused by ingestion of exotoxins that are present in the food
69
which has faster presentation of symptoms: food infection or toxication? why
intoxication has quicker symptoms because the toxin is ingested, not the microbe. Growth of the microbe is not required
70
list some symptoms of food poisoning
nausea, diarrhea, vomiting, fever, fatigue, muscle cramps
71
when do food poisoning symptoms occur
2-48 hours after ingestion
72
list 5 foodborne pathogens
bacteria, fungi, viruses, algae, protozoa
73
give an example of a fungal derived toxin
aflatoxin
74
what is aflatoxin caused by
growth in moist grains and nuts
75
list 2 algae that produce toxins
dinoflagellates and diatoms
76
describe a dinoflagellate's toxin effects/how it's produced
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
describe a diatom's toxin effect/how it works
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
give an example of a protozoa that produces toxins + what it causes
toxoplasma gondii causes toxoplasmosis
79
cause of toxoplasmosis?
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
symptoms of toxoplasmosis
swollen lymph nodes in neck, aches and pains, headache, fever
81
list 2 ways to control food-borne pathogens
biocontrol agents or predatory bacteria
82
describe how biocontrol agents can be used to control food-borne pathogens
its the process of using "living" organisms to combat the growth of pathogens in food (ie bacteriophages)
83
describe how predatory bacteria can be used to control food-borne pathogens
ie B bacteriovorus preys on other gram neg bacteria. they're multi-drug resistant, prey on biofilms
84
how does food fermentation work
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
list 3 major fermentations
lactic acid, propionic acid, alcoholic fermentation
86
describe sauerkraut production
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
describe yogurt production
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
describe chocolate production
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
define probiotic
live organism which when administered in adequate amounts confer a health benefit on the host
