Ch 7: Control of Microbial Growth Flashcards
What is the difference between disinfection and antisepsis?
Disinfection: treatment used to kill or inhibit microorganisms on inanimate objections
Antisepsis: treatment used to kill or inhibit organisms on living tissue
What is degerming?
Removing microbes from a limited area
What is sanitization?
Lower microbial counts on eating utensils
What is sepsis?
Presence of a toxin or pathogenic organism in blood and tissue
What is Asepsis?
Absence of contamination by unwanted bacteria
What factors influence the effectiveness of antimicrobial treatments?
- Number of microbes
- environmental influences
- time of exposure
- Microbial characterists
What type of environmental influences can influence the effectiveness of antimicrobial treatments?
- Presence of organic matter that protects from antimicrobials (i.e. biofilm)
- Suspensions rich in fats and proteins that protect from heat
- Temperature
What is the thermal death point (TDP) of a microbe?
THe lowest temperature at which all the microbes in a liquid culture will be killed in 10 minutes
What is the thermal death time (TDT) of a microbe?
The length of time required to kill all microbes in a liquid culture at a given temperature
What is the decimal reduction time (DRT or D value) of a microbe?
The length of time required to kill 90% of a bacterial population at a given temperature
How effective is boiling at killing microbes?
100 ℃ kills all vegetative bacterial pathogens, fungi and their spores, and most viruses within 10 minutes
EXCEPT ENDOSPORES
How does autoclaving work?
Sterilization by steam under pressure of about 15 psi (121 ℃)
Kill all organisms and endospores in about 15 minutes
What is pasteurization?
Eliminates pathogens and reduces food spoilage organisms without alter flavor of food
What is Vat pasteurization?
Pasteur’s original method
Heat 63 ℃ for 30 minutes
How is milk most commonly pasteurized today?
High-temperature short-time (HTST)
72 ℃ for 15 seconds
Why do pasteurization times and temperatures vary for different food products?
- Heat is less efficient in viscous foods
- Fats in foods are protective against heat
How does the dairy industry routinely measure the effectiveness of pasteurization?
Phosphatase assay (normal milk enzyme denatured in pasteurization)
How is milk sterilized?
Ultra-high-temperature: 140 ℃ for 2-5 seconds
What are some dry heat sterilization methods?
- Hot-air sterilization
- Direct flaming to a red glow
- Incineration
How does membrane filtration work?
Liquid is passed through a membrane (cellulose acetate, nitrocellulose, etc.) to remove microbes >0.22 μm (some can filter 0.01 μm)
High-efficiency particulate air (HEPA) filter remove microbes _____
>0.3 μm
In what situation is filtration the only practical way to eliminate undesirable microbes?
If you have something you don’t want destroyed by the heat of an autoclave
Refrigeration (0-7 ℃) is _____ for most microbes aside from psychotrophs.
Bacteriostatic
Deep-freezing renders microorganisms _____
Dormant
Does not necessarily kill them
