Définition : Value expressed in units of time, to quantify the effect of a sterilising treatment.
NB : Thermo-biological function, expressed in minutes, quantifying the lethal effect of moist heat on viable organisms.
Fo = Δt ∑10 T-121,11 / 10
The F function quantifying the sterilising effect depends on the parameters (D, z, PNSU)
The D value, or decimal reduction time, measures the time taken, at a given temperature, to reduce the concentration of bacteria by 90%. D can vary from 0.2 to 2 minutes of micro-organisms
-90% / Min to 121.1 ° C
Z is defined as the microbial destruction temperature, ie the number of degrees that lead to a variation of D by a factor of 10.
Z values vary between 6 and 13 according to the micro-organisms, in steam sterilisation between 100 and 130 ° C.
The PNSU is the probability of a non-sterile unit
This is the set of components to deal PNSU which is the Sterility Assurance Level (SAL).
In view of the decimated microorganisms, the values of D = 1 and z = 10 are taken into account at 121.11 ° C for the computation of Fo which enables the calculation of the sterilising value
Fo = Δt ∑10 T-121,11 / 10.