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Sanitization
Reduce number of microbes to a safe level
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Physical Methods of Control
Heat
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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
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Each microbial species has a thermal death time
for a given temperature
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Each species has a thermal death point:
the minimum temperature at which it dies in a given time period
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Incineration uses
direct flame to kill microbes
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Dry heat requires
- Long periods of exposure to high temperatures
- The heat changes microbial proteins and removes water, slowly burning the microbes
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Moist heat (like boiling water) is
- Faster and more effective at a lower temperature than dry heat
- It kills microbes by denaturing their proteins
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Boiling water may NOT
Kill all spores or inactivate all viruses
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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
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Autoclave
- Sterilization chamber
- When you increase pressure you can increase temperature
- Normal is 15 lbs/sq in = 121.5C
- Rusts sharp instruments
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What bacteria is used to check autoclave temperature?
Bacillus subtilis
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Pressurized steam is
Used in an autoclave to sterilize a variety of objects
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The prevacuum autoclave decreases:
- cycle time
- exposure of sensitive materials to steam
- Can then heat up t o134C at 28-30lbs
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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
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Pasteurization reduces
- bacterial populations in food and drink
- This reduces the chances of spoilage and disease
- Bacterial spores are not affected by pasteurization
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Pasteurization temps
- Holding method: 62.9C for 30 min
- Flash method: 71.6C for 15 sec
- Ultra: 82C for 3 sec
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Pasteurization Holding method
62.9C for 30 min
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Pasteurization Flash method
71.6C for 15 sec
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Pasteurization Ultra
82C for 3 sec
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Hot oil
- 160C for 60 min
- Doesn�t rust or dull instruments
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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
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Sand filtration is used for
Beer, water, pharmaceuticals
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Cellulose acetate and polycarbonate filters are used to
- Sterilize water
- Trap bacteria
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Air can be filtered using
A high-efficiency particulate air (HEPA) filter
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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
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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
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Drying food removes
The water necessary for microbes to live
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Salting food causes
Water to diffuse out of organisms, causing dehydration and death
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Low temperatures for food lowers
Microbial metabolic and growth rates, retarding spoilage
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Antiseptics
Are used on living tissue
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Disinfectants
Are used on non-living surfaces
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