Microbial growth

• Sterilization


  Killing or removing all forms of microbial life (including endospores) in a material or an object
• Commercial Sterilization


  Heat treatment that kills endospores of Clostridium botulinum the causative agent of botulism, in canned food
• Disinfection


  Reducing the number of pathogenic microorganisms to the point where they no longer cause diseases. Usually involves the removal of vegetative and non- endospore forming pathogens.
• Disinfectant


  Applied to inanimate objects
• Antiseptic


  Applied to living tissue (antisepsis)
• Degerming


  Mechanical removal of most microbes in a limited area
• Sanitization


  Use of chemical agent on food-handling equipment to meet public health standards and minimize chances of disease transmission
• Sepsis


  Bacterial contamination
• Asepsis


  Absence of significant contamination
• Aseptic techniques


  Used to prevent contamination of surgical instruments, medical personnel, and the patient during surgery, and to prevent bacterial contamination in food industry
• Bacteriostatic Agent


  An agent that inhibits the growth of bacteria, but does not necessarily kill them
• Germicide


  An agent that kills certain microorganisms
• Bactericide


  An agent that kills bacteria
• Viricide


  An agent that inactivates viruses
• Fungicide


  An agent that kills fungi
• Sporocide


  An agent that kills bacterial endospores of fungal spores
• Factors influencing effectiveness of antimicrobial treatment

  • Number of Microbes
  • Type of Microbes
  • Environmental influences
  • Time of Exposure
• Thermal Death Point (TDP)


  Lowest temperature at which all of the microbes in a liquid suspension will be killed in ten minutes
• Thermal Death Time (TDT)


  Minimal length of time in which all bacteria will be killed at a given temperature
• Decimal Reduction Time (DRT)


  Time in minutes at which 90% of bacteria at a given temperature will be killed
• Moist Heat


  • Kills microorganisms by coagulating their proteins
  • Much more effective than dry heat
• Autoclave


  Chamber which is filled with hot steam under pressure, preferred method of sterilization
• Pasteurization


  Developed by Louis Pasteur to prevent the spoilage of beverages, used to reduce microbes responsible for spoilage
• High Temperature Short Time Pasteurization (HTST)


  Milk is exposed to 72°C for 15 seconds
• Ultra High Temperature Pasteurization (UHT)


  Milk is treated at 140°C for 3 seconds and then cooled very quickly in a vacuum chamber
• Filtration


  Removal of microbes by passage of a liquid or gas through a screen like material with small pores
• High Efficiency Particulate Air Filters (HEPA)


  Used in operating rooms and burn units to remove bacteria from air
• Membrane Filters


  Uniform pore size, used in industry and research
• Refrigeration


  Temperatures from 0 to 7°C, bacteriostatic effect
• Freezing


  Temperatures below 0°C.
• Dessication


  In the absence of water, microbes cannot grow or reproduce, but some may remain viable for years
• Osmotic Pressure


  The use of high concentrations of salts and sugars in foods is used to increase the osmotic pressure and create a hypertonic environment
• Plasmolysis


  As water leaves the cell, plasma membrane shrinks away from cell wall, cell may not die but usually stops growing
• Ionizing Radiation


  Gamma rays, X rays, electron beams, or higher energy rays, dislodge electrons from atoms and form ions, cause mutations in DNA and produce peroxides
• Ultraviolet light (Nonionizing Radiation)


  Wavelength is longer than that of ionizing radiation
• Yeasts and molds


  • More resistant to high osmotic pressures
• Staphylococci spp

  • That lives on the skin and fairly resistant to high osmotic pressure
• Ionizing Radiation


  1. Dislodge electrons from atoms and form ions

  2. Cause mutations in DNA and produce peroxides
• Ionizing Radiation


  Have short wavelengths (less than 1 nanometer)
• Ionizing Radiation


  • Used to sterilize pharmaceuticals and disposable medical supplies
  • Food industry is interested in using ionizing radiation