Subtopic: Kinetics of microbial death – pasteurization and sterilization of milk and other liquid foods
Question Statement:
A bacterial spore suspension has a decimal reduction time ($D_{121}$ value) of $1.5\text{ minutes}$ at $121^\circ\text{C}$. The thermal holding time in minutes required at $121^\circ\text{C}$ to achieve a $12\text{-D}$ reduction of this bacterial population is ________ (answer in integer).
Answer Key:
18
Step-by-Step Solution & Explanation
The thermal death time $F$ for an $n$-decimal reduction is:
$F = n \times D$
Given:
• Decimal reduction time $D = 1.5\text{ minutes}$
• Number of log reductions $n = 12$
$F = 12 \times 1.5\text{ min} = 18\text{ minutes}$