2. Principle-Denaturation & coagulation of
proteins due to the latent heat present in
steam
Advantages of steam –Latent heat liberated
on condensing on a cooler surface increases
the temprature of that surface
What is Moist heat Sterilization?
6/11/2013
3. Types of Moist heat Sterilization
• Pasteurization
• Inspissation or Fractional Sterilization
Hot water below
boiling point
• Tyndallization or Intermittent
Sterilization
Boiling water
/steam at atm pr
• AUTOCLAVESaturated steam
6/11/2013
4. Pasteurization
6/11/2013
• 63 C for 30
minutes
Holder
Method
•72 C for 15-
20 seconds
Flash
Process
Heat labile fluids may be disinfected
5. It is the process of
thickening by dehydration
6/11/2013
Inspissation
Media such as
Lowenstein –Jensen
media and Loeffler’s
serum are rendered
sterile by heating at
80-85 C for half an
hour on three
consecutive days
6. 6/11/2013
Tyndallisation
Principle: The first exposure kills all
vegetative bacteria and the spores
since they are in a favourable
medium will germinate and be killed
on subsequent occasions
Though generally adequate this
method may fail with spores of
certain anaerobes and thermophiles
7. The Autoclave was invented by Charles
Chamberland in 1879
AUTOCLAVE
6/11/2013
8. Definition
Autoclave is a pressurized
device designed to heat
aqueous solutions above
their boiling point at
normal atmospheric
pressure to achieve
sterilization
6/11/2013
9. Reliable sterilization with moist heat requires
temperatures above that of boiling water.
These high temperatures are most commonly achieved
by steam under pressure in an autoclave. .
Need for autoclaving:
6/11/2013
Autoclaving is the preferred method of
sterilization unless the material to be
sterilized can be damaged by heat or
moisture
10. 6/11/2013
Liquid H2O cannot be
heated above 100°C in an
open vessel
At 100°C boils
H2O heated in a sealed vessel
Pressure rises
Boiling point of H2O is raised
13. Biological indicators are the only process indicators that directly monitor the lethality of a
given sterilization process. Spores used to monitor a sterilization process have
demonstrated resistance to the sterilizing agent and are more resistant than the
bioburden found on medical devices.
Bacillus stearothermophilus
Thermophilus aquaticus
Spore Test
6/11/2013
If the autoclave does not reach the
right temperature the spores
will germinate when incubated and
their metabolism will change the
color of a pH –sensitive chemical.
