Question

Explain what decimal reduction time (DRT) is. For an organism with DRT of 10 minutes at 100°C, how long does one need to treat it at 100°C to kill 99.9% of viable cells? [SHORT ANSWER]

Answer 1

The D value (Decimal reduction value) is the time interval required to kill 90% of the cell population in given conditions.

Given that the D value for this organism is 10 minutes at 100⁰C. It means that the organism will be killed up to 90% in 10 minutes heat exposure and the 10% will remain viable.

SO for killing 99.9% of viable population

In the first 10 minutes the remaining viable population = 10%

So if it will be given exposure of another 10 minutes then, 90% of 10% = 9

So another 9% will be killed and 1% will be retained

Total killing after

Minutes = 90+9 = 99%.

SO more killing required. Now another 10 minutes exposure will lead to killing of 90% of remaining 1% viable cells = 0.9%

So nw the total killing % = 99+0.9 =99.9%.

SO it will require 30minutes to kill 99.9% of the viable cells.