Lecture 13

Question 1

Define disinfect

Answer 1

spores are not killed, but pathogens should be eliminated

Question 2

Define sterilize

Answer 2

spores are killed along with vegitative cells, viruses, fungi, and protists

Question 3

How can drug cocktails be made more effective?

Answer 3

mix drugs with very different modes of action

Question 4

What is the method of choice in controlling microorganisms? Why?

Answer 4

heat sterilization

easy to control
leaves no residue
organisms can’t develop resistance

Question 5

What is a disadvantage to using heat sterilization?

Answer 5

heat labile compounds are destroyed

Question 6

Name the 2 types of physical methods to control microorganisms which involve heat

Answer 6

dry heat

moist heat

Question 7

Define dry heat sterilization

Answer 7

stays dry the whole time
OR
ends up dry at the end of sterilization

Question 8

Which is a faster process:

dry heat or moist heat sterilization?

Answer 8

moist heat

because proteins are more stable in dry heat

Question 9

Name 2 different types of dry heat sterilization

Answer 9

Incineration

hot air oven

Question 10

What happens during incineration?

Answer 10

very rapid oxidation of all organic material (organism burns)
heat speciment between 700-1500 degrees C
Only (inorganic) minerals left over

Question 11

What is incineration used for? Give an example

Answer 11

biological waste disposal
EX:
Mad cow disease; incineration is the only certain way to get rid of the prions

Question 12

What are prions?

Answer 12

amino acids which have folded incorrectly

Question 13

Can you autoclave to remove mad cow disease?

Answer 13

Not really
one could autoclave the animal at 132 degrees for an hour, but the size and thickness of the cow would be difficult to assure full penetration

Question 14

What is the mode of action of incineration?

Answer 14

Oxidation
Addition of oxygen = more intense oxidation
Removal of hydrogen = less intense (Protein oxidation)

Question 15

What are the guidelines for time and temp of a hot air oven as a form of sterilization?

Answer 15

160 degrees C for 2 hours

Question 16

How is the penetration of a hot air oven?

Answer 16

it has poor penetration

Question 17

What is the mode of action of a hot air oven?

Answer 17

dehydration- removal of water
protein oxidation- removal of hydrogen, mild
protein coagulation- protein falls out of solution and solidifies (the protein is destroyed) [for an example cook some eggs]

Question 18

Is moist heat sterilization slow or fast?

Answer 18

very fast

Question 19

Name 6 types of moist heat sterilization

Answer 19

boiling
free flowing steam
steam under pressure
high volume autoclave
pasteurization
milk sterilization

Question 20

How can the boiling temperature of water be increased?

Answer 20

adding salt (NaCl or sodium carbonate)

Question 21

What does scrubbing do?

Answer 21

decreases load and washes off spores

Question 22

describe some characteristics of boiling

Answer 22

disinfects after 15 minutes

will kill spores after 5-9 hours

Question 23

Does boiling sterilize or disinfect?

Answer 23

disinfect

the time it takes to kill spores is too long to be considered a viable sterilization method

Question 24

What is the advantage of using free flowing steam?

Answer 24

less water log

Question 25

Does free flowing steam sterilize or disinfect?

Answer 25

disinfect

Question 26

does steam under pressure sterilize or disinfect?

Answer 26

sterilize

Question 26

Is steam under pressure more effective at killing microorganisms than a hot air oven?

Answer 26

yes

moist air at 121.5 degrees is more sterilizing than dry air at the same temperature

Question 27

What is an example of a way to sterilize using steam under pressure?

Answer 27

an autoclave

Question 28

What does pressure do that makes steam under pressure more effective than boiling?

Answer 28

the pressure raises the water temperature

Question 29

Are prions destroyed in a high vacuum autoclave?

Answer 29

no

Question 30

What is the goal of pasteurization?

Answer 30

destroying all pathogens while maintaining the most flavor of the sample

Question 31

What is the difference between batch and flash pasteurization

Answer 31

Batch is done in large quantites. Temp is lower (62.9), time is longer (30 minutes)
Flash is done in smaller batches at a hotter temperature (71.6) for a shorter amount of time (15 seconds)

Question 32

What does the batch method of pasteurization kill?

Answer 32

Coxiella burnetti (Q-fever)
mycobacterium bovis (a form of TB)

Question 33

What is milk sterilization?

Answer 33

heat the milk to 140 degrees for less than a second

gives the milk a very long shelf life even without refrigeration

Question 34

What is the difference between milk sterilization and pasteurization?

Answer 34

Milk sterilization is done at higher temperatures (140 degrees) for less time (<1 second); does not taste good
Pasturization is done at a lower temperature for longer (time and temp vary by the method)

Question 35

What is the mode of action for moist heat?

Answer 35

protein coagulation