Unit 2: 13.2 Using Physical Methods To Control Microorganisms Flashcards
How does heat kill microbes
Heat alters membrane and denatures proteins
Thermal death point (TDP)
The lowest temperature at which all microbes are killed in a 10 min exposure
Which endospores forming bacteria is heat resistant
Clostridium botulinum
Thermal death time (TDT)
Time needed to kill all microorganisms in a sample at a given temperature
Is boiling an effective way to kill endospores
No some endospores can live up to 20 hours of boiling
Dry heat sterilization
Involves application of high heat
Which is better dry heat sterilization or moist heat sterilization
Moist heat because it penetrates cells better than heat does
Autoclaves
Raise temps above the boiling point of water to sterilize items. Can kill endospores
-type it moist heat sterilization
Which spores are used to see the effectiveness or how sterile protocols are?
- Geobacillus stearothermophilius
- Bacillus subtilis
- Bacillus pumilus spores
Pasteurization
Kills pathogens and reduces the number of spoilage causing microbes while maintains food quality
-developed by Louis Pasteur
Desiccation/dehydration
Drying can control microbial growth, not kill, because microbes require water to live
Lyophilization
An item is rapidly frozen and placed under vacuum so that water is lost
-combines cold demo and desiccation so it is effective in microbial growth control
What is better for microbial growth control, hypertonic or hypotonic environments?
Hypertonic, because it draws water out of microbes
Ionizing radiation
Strong enough to pass through cell and alter/damage cell and cause mutations that lead to cell death
- effective way to sterilize heat sensitive/packaged materials
- X-rays
- gamma rays
Non-ionizing
Commonly used for disinfection and uses less energy than ionizing
- controls microbial growth not kill
- UV rays
