HEATING : Most effective and widely used method
a) moist heat b ) dry heat
MOIST HEAT :
All moist heat sterilization processes consist
of four phases in their cycles:
Heating phase
Sterilization phase
Evacuation and cooling phase
Drying phase
can be used in sterilization at different temperatures
at temperatures below 100 C : pasteurization
at temperatureof 100 C : tyndallization
at temperatures above 100C : autoclave
autocleaving : saturated steam under pressure is widely used inexpensive and nontoxic: the most commonly used sterilization cycle is use of saturated steam heated at 121°C for 15 min .
If no moisture is present, then the temperature
must reach 160°C. dry heat sterilization requires prolonged exposure times and damages many instruments
pasteurization : Pasteurization is not a sterilization process; its
purpose is to destroy all pathogenic microorganisms. However, pasteurization does not destroy bacterial spores
pasteurization is generally ~70°C (158°F) for
30 minutes
Tyndallization: is a process for decontamination that
can be used to kill spores and decontaminate something that will not withstand the higher temperature and pressure or unpressurized heating for a prolonged period at a temperature of up to 100°C. It essentially consists of heating the substance to boiling point (or just a little below boiling point) and holding it there for 15 minutes, three days in succession. After each heating, the resting period willallow spores that have survived to germinate into bacterial cells; these cells will be killed by the next day's heating
DRY HEAT : It is used for materials that cannot be sterilized
by steam because of the possibility of moisture damage or because the material is impermeable to steam (oils, powders, sharp instruments, and glassware). Temperature range is 150-180°C and time range is
1-2h - hot air oven