Question

Determine the F value for a 12 D process for Clostridium botulinum at 250 ^oF, based on the following data. After heating for 3 minutes at 250 ^oF, the microbial count was reduced from 10⁵ count/mL to 10² counts/mL (3 log reduction).

Answer 1

F =12D

F value is the time required to kill a given microbial population at a specified temperature. It is a multiple of D value

D value is the decimal reduction time. It is the time required to reduce bacterial population by one log cycle.

Here the microbial population is reduced from 10⁵ count/mL to 10² counts/mL ( 3 log cycles) in 3 minutes

3 minutes $\rightarrow$ 3 log cycle

1 minute $\rightarrow$ 1 log cycle

So the D value is 1 minute at 250 ^o F.

F =12D

F =12 x 1 =12 minutes