Microbiology Chatper 24 Microbial Control.txt

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Microbiology Chatper 24 Microbial Control.txt
2010-07-29 14:19:45
Microbiology Microbial Control

Microbiology Chatper 24
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  1. Sterilization
    No life
  2. Sanitization
    Reduce number of microbes to a safe level
  3. Physical Methods of Control
  4. Heat Is One of the Most Common Physical Control Methods
    • Sterilizes
    • At heats above the growth range:
    • proteins and nucleic acids are destroyed
    • water is removed
  5. Each microbial species has a thermal death time
    for a given temperature
  6. Each species has a thermal death point:
    the minimum temperature at which it dies in a given time period
  7. Incineration uses
    direct flame to kill microbes
  8. Dry heat requires
    • Long periods of exposure to high temperatures
    • The heat changes microbial proteins and removes water, slowly burning the microbes
  9. Moist heat (like boiling water) is
    • Faster and more effective at a lower temperature than dry heat
    • It kills microbes by denaturing their proteins
  10. Boiling water may NOT
    Kill all spores or inactivate all viruses
  11. Boiling water
    • Denatures proteins
    • 10 min for most bacteria
    • 30 min for some fungal and protozoan spores
    • 2 hours for bacterial spores
    • 30 min is the minimum for safety
  12. Autoclave
    • Sterilization chamber
    • When you increase pressure you can increase temperature
    • Normal is 15 lbs/sq in = 121.5C
    • Rusts sharp instruments
  13. What bacteria is used to check autoclave temperature?
    Bacillus subtilis
  14. Pressurized steam is
    Used in an autoclave to sterilize a variety of objects
  15. The prevacuum autoclave decreases:
    • cycle time
    • exposure of sensitive materials to steam
    • Can then heat up t o134C at 28-30lbs
  16. Fractional sterilization is used for
    • Sterilization if materials are not suited to the autoclave
    • Heat to 100C for 30 min
    • Steam
    • AKA Tyndalization
    • Repeat at least 2 more times
    • Kills newly hatched spores on repeated reheating
  17. Pasteurization reduces
    • bacterial populations in food and drink
    • This reduces the chances of spoilage and disease
    • Bacterial spores are not affected by pasteurization
  18. Pasteurization temps
    • Holding method: 62.9C for 30 min
    • Flash method: 71.6C for 15 sec
    • Ultra: 82C for 3 sec
  19. Pasteurization Holding method
    62.9C for 30 min
  20. Pasteurization Flash method
    71.6C for 15 sec
  21. Pasteurization Ultra
    82C for 3 sec
  22. Hot oil
    • 160C for 60 min
    • Doesn�t rust or dull instruments
  23. Filtration
    • Traps Microorganisms
    • Uses porcelain, cellulose or ceramic
    • As fluid passes through a filter, organisms above a certain size threshold are trapped in the pores
  24. Sand filtration is used for
    Beer, water, pharmaceuticals
  25. Cellulose acetate and polycarbonate filters are used to
    • Sterilize water
    • Trap bacteria
  26. Air can be filtered using
    A high-efficiency particulate air (HEPA) filter
  27. Ultraviolet Light
    • 265 wavelength is best to destroy DNA
    • Causes thymine molecules to link together
    • Errors in protein synthesis and impairment of chromosome replication occur
    • Doesn�t bend or go around corners
  28. X rays and gamma rays (ionizing radiations)
    • Force electrons out of microbial molecules
    • Hard to control
    • More effective on G+
    • This affects cell metabolism and physiology
    • Used to control microbes in food
  29. Drying food removes
    The water necessary for microbes to live
  30. Salting food causes
    Water to diffuse out of organisms, causing dehydration and death
  31. Low temperatures for food lowers
    Microbial metabolic and growth rates, retarding spoilage
  32. Antiseptics
    Are used on living tissue
  33. Disinfectants
    Are used on non-living surfaces