Subtopic: Kinetics of microbial death – pasteurization and sterilization of milk and other liquid foods
Question Statement:
In thermal processing of food, the $z$-value is defined as the temperature increase ($^\circ\text{C}$) required to:
Options:
(A) Reduce the $D$-value by a factor of 10 (one logarithmic cycle)
(B) Inactivate $90\%$ of microbial population at constant temperature
(C) Double the sterilization rate
(D) Reduce activation energy by half
Answer Key:
A
Step-by-Step Solution & Explanation
The $z$-value is the temperature change in $^\circ\text{C}$ or $^\circ\text{F}$ required to alter the thermal death time ($D$-value) by tenfold (one log cycle) on the thermal death time curve.