Work out thermal death time instantly with clear inputs, formula shown and shareable results.
Thermal death follows first-order kinetics: each D value of holding time reduces the population tenfold. Time required is the log reduction needed times the D value at the process temperature, less any lethality already accumulated during come-up. A 6-log reduction needs 6 D values.
Thermal death time
Time = log10(N0 / N) x D value
Survivors
N = N0 x 10^(-time / D)
Thermal process design is food safety critical and must be established by a competent process authority using validated D and z values for the target organism.
From thermal resistance studies on the specific organism in the specific food matrix. D values vary greatly with pH, water activity, fat content and prior stress, so generic values are not adequate for validation.
It is the conventional performance standard for pathogen reduction in many regulations, chosen to bring realistic initial contamination to a negligible probability of a surviving cell.