At a fixed temperature, a thermal treatment gives a 2-log₁₀ reduction of non-thermotolerant pathogenic microorganisms in 20 minutes. Under the same conditions, find the time for 99.999% removal, in integer minutes.
A two-log reduction leaves $10^{-2}$ of the initial population in 20 min, so the decimal reduction time is $D=20/2=10$ min per log. Removal of 99.999% leaves .001%,$10^{-5}$ of the original, requiring five logs. With the same log-linear kinetics,$t=5D=\mathbf{50}$ min.
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