Lethality value

The lethality value (L), also called lethality rate or partial F value (F derived from Fahrenheit ), indicates how effectively microorganisms with a defined heat resistance are killed if they are exposed to a certain temperature for one minute. The standard is a temperature of 121.1 ° C (= 250 ° F), which has a lethality value of one (L = 1). All other lethality values ​​are fractions of this value.

The decimal reduction time and the Z value play a role in calculating the specific lethality value when examining a sample .

The L-value can be calculated as follows:

${\displaystyle L={\frac {F(0)}{F(t)}}={\frac {D(121,1)}{D(t)}}=10^{\frac {T-121,1}{z}}}$

Assuming a Z value of 10, then an L value of 0.1 corresponds to

• heating to 101.1 ° C for 10 minutes
• heating to 111.1 ° C for 1 minute
• heating to 121.1 ° C for 0.1 minutes = 6 seconds

With the help of the temperature curve during a heating process, with a known Z-value, one can calculate the killing effect that would have been had with a sudden heating to 121.1 ° C (followed by a sudden cooling).

source

Dr. Nagel on the preservation of food (PDF; 207 kB)

Bayer CropScience on the characteristic parameters of sterilization (PDF; 426 kB)