The F0 value is defined as the thermal lethality time required to eliminate all microorganisms present in a sample, by exposing them to a temperature of 121.1ÂºC and it is expressed in minutes.

To calculate the F0 value, average the temperature of each probe during the sterile hold and then average the different temperatures to get one single temperature. Use the formula shown in below to estimate the F0 value:

Where,

F0 Value = Equivalent Exposure Time

Î”t = the time interval between two temperature readings

T = the temperature at time t of the product under sterilization

z = temperature coefficient (assumed as 10°C)

Let consider sterilization hold time of 30 min. at constant 121.1°C. Put this in above equation –

Thus, F0 = 30 min. (This is an ideal condition for steam sterilization).

Now consider sterilization hold time of 30 minutes at constant 110°C instead of 121.1°C, in a similar manner as above –

Thus, F0=2.33 min.

Hence, 30 minutes of sterilization at 110°C is lethally equivalent to 2.33 min. of sterilization at 121.1°C. (Compare this sentence with the definition of F0 value for easy understanding).

#### Related FAQs

**What is D value and Z value?**

D-value is the time (t) required at a specified temperature (T) to reduce the microbial population from 100% to 10% (1 log reduction). z-value is the number of degrees the temperature required to increase, which will effect a 10-fold variation of D-value.

**What is F value in microbiology?**

The F value for a process is the number of minutes required to kill a known population of microorganisms in a given sample under specified conditions.

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**Resource Person:** Saket Yeotikar

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