Heat generated through application of high temperatures acts by disrupting membranes and denaturing proteins and nucleic acids. Burning, however, is a bit excessive for everyday usage.
Transmissible agents (such as spores, bacteria and viruses) can be eliminated through sterilisation. This is different from disinfection, where only organisms that can cause disease are removed.
Some of the methods used to achieve sterilization are:
In a dry air oven, it takes two hours at 160°C to kill spores of the bacterium Clostridium botulinium (associated with canned food). Using saturated steam, the same spores are killed in just five minutes at 121°C, proving that moist heat is more effective than dry heat.
To be effective against spore forming bacteria and viruses, autoclaves need to:
The efficiency of the sterilization process depends on two major factors. One of them is the thermal death time, i.e. the time microbes must be exposed to at a particular temperature before they are all dead. The second factor is the thermal death point or temperature at which all microbes in a sample are killed.
The steam and pressure ensure sufficient heat is transferred into the organism to kill them. A series of negative pressure pulses are used to vacuum all possible air pockets, while steam penetration is maximized by application of a succession of positive pulses
1.Cycle for fabrics, assembled filter units and discard loads.
2.Cycle for laboratory plastic and glassware.
3.Cycle mainly used for discard loads.
Process performance can be confirmed by monitoring colour changes on indicator tape often taped onto packages or products to be autoclaved. Biological indicators such as the Attests can also be used. These contain Bacillus sterothermophilus spores, which are amongst the toughest organisms an autoclave will have to destroy. After a run in an autoclave, the internal glass in the Attest vial is shattered, allowing the spores into a differential liquid medium. If the autoclave has destroyed the spores, the medium remains a blue colour. Otherwise, the spores will metabolize, causing a yellow colour change after two days of incubation at 56°C.
A control system must therefore provide flexibility in the way in which accurate and repeatable control of the sterilisation is achieved and will include the following features:
The EyconTM Visual Supervisor is an ideal solution for this application.