B.1 General
There are several, well-established, time–temperature relationships for moist heat disinfection which are
regarded as equally acceptable. Clearly temperatures other than those chosen, when maintained for an
appropriate time, will also be capable of producing a disinfected product.
For a moist heat disinfection process, a particular time at a particular temperature can be expected to have a
predictable lethal effect against a standardized population of organisms. If particularly resistant organisms are
chosen and it is assumed that they are present in numbers in excess of that likely to be encountered in real
product, then it is possible to define standard exposure conditions which will always yield a disinfected product
in a correctly operated WD. Actual exposures can then be related to these standard exposure conditions.
Levels of disinfection can be specified by regional or national authorities.
Definition of moist heat disinfection processes may be achieved by means of the A0 method which uses a
knowledge of the lethality of the particular process at different temperatures to assess the overall lethality of
the cycle and express this as the equivalent exposure time at a specified temperature.
"A” is defined as the equivalent time in seconds at 80 °C to produce a given disinfection effect.
When the z value is 10 °C, the term A0 is used.
The A0 value of a moist heat disinfection process is the equivalent time in seconds at a temperature of 80 °C
delivered by that process to the product with reference to microorganisms possessing a z value of 10 °C.