Holding a population of microorganisms having a z value of 1

Holding a population of microorganisms (having a z value of 18 F) at 240 F for one minute has the same lethal effect as holding the population at 250 F for the following minutes: (select the correct answer – answers may be rounded).

0.39

0.13

1.72

0.07

0.10

0.15

2.05

0.21

0.28

0.51

2.15

Solution

Ans is 0.28 minutes

This can be calculated using formula

t = F_• × 10 ^{(240 - T) / z}

t is time

F_o is time taken to kill 1 million spores = 1 min

Z = 18 ^° F

putting the values we get t = 0.28 minutes