62 0c for 30 minutes(Holder method) or 72 0c for 15 seconds (Flash method) followed by rapid cooling to discourage bacterial growth. Uses: . Pasteurization of milk . Preparation of bacterial vaccines. Autoclaving : Steam under pressure It is based on the principle that when water is boiled at increased pressure, hot saturated steam will be formed which penetrates and gives up its latent heat when it condenses on cooler objects. Hot saturated steam in autoclaving acts as an excellent agent for sterilization because of:
1. 2. 3. 4.
high temperature High latent heat ability to form water of condensation
Method of using an autoclave
Add the correct volume of water to the autoclave.
Place the bottles and tubes of culture media with caps loosened in the inner chamber of the autoclave.
Secure the lid i.e. Open the air-outlet and close the draw-off knob.
Adjust the safety valve to the required pressure and temperature.
When the required pressure and temperature has been reached, begin timing.