; CHEMICAL _ PHYSICAL METHODS FOR KILLING MICROBES
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CHEMICAL _ PHYSICAL METHODS FOR KILLING MICROBES

VIEWS: 6 PAGES: 21

  • pg 1
									  PHYSICAL METHODS FOR
    KILLING MICROBES
• Sterilization methods
  –   Incineration
  –   Autoclave
  –   Dry heat oven
  –   Filter sterilization
  –   Ultra violet light
  –   Gamma radiation
The direct flame represents a
 rapid sterilization method

         Incineration
 The autoclave uses
moist heat and pressure
        Boiling water involves
              moist heat


• This is not a reliable method for sterilization
  unless tyndallization is used.

• Why not?
 Pasteurization does not sterilize

• It is used to kill unwanted or harmful
            microbes
• Why doesn’t it sterilize?
       Hot-air (dry-heat) oven

Time and Temperature: 338F for 11/2 hours
Filter Sterilization
Filtration traps microorganisms
  Ultraviolet light can be used to
     control microbial growth

    UV light attacks the cell’s DNA
What are some disadvantages in the use of
 UV for sterilization?
The Ionizing and Electromagnetic
      Spectrum of Energies
Thymine Dimers of DNA form
  when exposed to UV light
Thymine Dimers
CHECK MOLES FOR THESE CHANGES
 GAMMA RADIATION

 A widely used method for sterilizing
   materials that would be adversely
altered by heat (plastics, lensed equip.
       heart-lung machines etc).
Logo for gamma radiation
Look for this logo on those foods that have been treated with gamma
             radiation, such as meats, and produce.
PRESERVATION METHODS

            Drying (dehydration)
               Method
            Salting Method
            Low pH Method
  Do these methods sterilize the
           food? Explain.
General Principles of
 Chemical Control
Resistance of microbes to chemical
              agents
Disinfectants
Killing Action of certain metals
Killing Action of Some Antiseptics

								
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