Bacterial Visualization, Growth and Control Flashcards Preview

Microbiology > Bacterial Visualization, Growth and Control > Flashcards

Flashcards in Bacterial Visualization, Growth and Control Deck (112)
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91

heat treatments

moist heat
dry heat
flame sterilization
pasteurization

92

moist heat

steam
autoclave

93

dry heat

oven
less effective than moist heat

94

flame sterilization

aseptic transfer of organisms

95

pasteurization

briefly expose perishable fluids to high heat

96

flash pasteurization

continuous, high temp, short time
milk 72C for 15 seconds- kills all pathogens

97

continuous ultra high temp pasteurization

140 C for 1 to 3 seconds
may affect taste

98

batch (vat) pasteurization

63C, 30 min

99

superheated steam

sterilization
store liquids at room temperature without spoiling
product may degrade- dairy coffee creamer

100

refrigeration

low temp does not kill but slows metabolism, reproduction

101

radiation

damages DNA and denatures proteins

102

radiation types

ionizing
non ionizing
microwaves

103

ionizing radiation

high energy, penetrating, X rays, gamma rays
penetrates covers- food, medical supplies, mail

104

non ionizing radiation

lower energy, non penetrating, uv light
does not penetrate covers- wrappers, surfaces
requires direct exposure to radiation

105

microwaves

less effective than bacteria
longer wavelength, lower energy

106

osmotic treatment

high solute concentration (salt, sugar)
create hypertonic environment to remove water from cells but do not kill cells

107

filtration

filters remove most bacteria- does not remove viruses
sterilize liquids or gases damaged by heat

108

chemical treatments

kills bacteria or reduces numbers to low levels

109

chemical treatment examples

bleach- kill bacteria on slides; pipettes
lysol- clean bench
isopropanol- kills bacteria, cleans surface, evaporates quickly
soap- emulsifies lipids, helps remove bacteria from surfaces
ethylene oxide (gas)- deeply penetrating, requires more time; used to sterilize space craft returning from moon and Mars, sterilize medical equipment

110

effectiveness of control treatments depends on

-characteristics of organism being treated
-number of cells in colony and growth stage colony is in
-organic substances in environment may interfere with treatments
-temperature and length of exposure time

111

D-value

decimal reduction time
measures rate of decline in response to heat treatment
time in minutes required to kill 90% of population at given temperature
90% die in 10 minutes- 90% of remaining 10% die in next 10 minutes

112

Microbial death graph

higher temp, shorter time