Chapter 11

• As a basic rule of thumb, for every additional Log reduction number you add a 9 to the percentage reduction – so a log reduction of 3, as illustrated above, is a 99.9% reduction compared with a log reduction of 6 which is equivalent to a 99.9999% reduction.
• Chemical methods are best for sterilization if heat or radiation can damage the object. Chemical agents are best if need if antisepsis needs to occur.
• Physical disinfection is best if objects are not damaged by heat or radiation. 
• Filtration can be used if the bacterial components are able to be caught in a filter. Also if heat cannot be used. 
• B lactum drugs have a b lactum ring. Bacteria produce b lactamase which attacks the ring. B lactamase inhibitor inhibits b lactamase. 
• Antimicrobial agents

  Any chemical, physical or biological agent that controls microbial growth
• Types of antimicrobial agents

  • Chemical agents
  • Physical agents
  • Mechanical methods
• Chemical agents

  • Use gases and liquids for usually disinfection and antisepsis, not sterilization
• Physical agents

  • Heat, moist heat, and radiation
  • Examples: flaming, pasteurization, ionizing radiation
• Sterilization methods

  • Flaming
  • Irridation
  • Autoclaving
• Disinfection methods

  • Boiling
  • Microwaves
  • Pasteurization
• Filtration

  • Filtration of air decontaminates
  • Filtration of liquids sterilize
• Pasteurization

  A moderate amount of heat is applied to food to reduce the number of microbes, after going through the process there is still microorganisms just not vegetative ones, and endospores remain
• Sterilization

  Completely remove all viable microorganisms
• Death of a Microbe

  Where substantial damage has occurred to the microbe's metabolically and structurally, resulting in the loss of the ability to reproduce
• • cidal


  Refers to where microbes are killed under appropriate conditions
• • stasis


  Refers to where microbial growth and multiplication of microbes are inhibited under appropriate conditions
• Ionizing radiation

  • Includes gamma rays, and X-rays, and can be sterilizing
  • Causes mutations in the DNA and damages proteins that repair DNA
  • Causes chemical changes in organelles and produces toxic substances
• Non Ionizing radiation

  • Includes UV radiation, have poor penetration, and can be sterilized
  • Excites atoms which causes abnormal bonds which results in mutations
  • Works best at sterilizing clear objects and the surface of objects
• Forms of moist heat

  • Boiling
  • Autoclaving
  • Pasteurization
• Moist heat

  Can perform sterilization and disinfection
• Dry heat

  • Refers to where there is low moisture content that is applied with a flame or electric heating coil
  • Can only perform sterilization
• Environmental factors used to preserve food

  • Heat to sterilize
  • Cold to slow down microbial growth
  • Drying to prevent water from supporting microbial growth
  • Irradiation to kill microbes
  • Adding salt or sugar to decrease microbial growth
• Chemical disinfectants

  • Rapid action at low concentrations
  • Soluble in water
  • Long shelf life and stability
  • Broad spectrum antimicrobial action without toxicity
  • Noncorrosive or staining
  • Affordable and readily available
  • Deodorizing and sanitizing
• Pore size of Filters

  Larger filters can only filter out bacteria, smaller filters are able to filter out viruses and bacteria
• Chemical concentration


  Can withstand different concentrations, there is a range usually between 60-90 where no growth will occur