Subtopic: Kinetics of microbial death – pasteurization and sterilization of milk and other liquid foods
Question Statement:
A bacterial spore suspension has an initial population of $10^6\text{ spores/mL}$. The decimal reduction time ($D$-value) of the spores at $121.1^\circ\text{C}$ is $1.5\text{ minutes}$. Calculate the heating time in $\text{minutes}$ at $121.1^\circ\text{C}$ required to reduce the spore population to $1\text{ spore/mL}$.
Answer Key:
9
Step-by-Step Solution & Explanation
Number of decimal log reductions:
$n = \log_{10}\left(\frac{N_0}{N}\right) = \log_{10}\left(\frac{10^6}{1}\right) = 6$
Required process time:
$F = n \times D = 6 \times 1.5 = 9.0\text{ minutes}$