Question

Decimal reduction time is the time required at a given condition to

• A. Change the temperature of a process by \(10^\circ\text{C}\)
• B. Achieve one log reduction in relevant microorganism
• C. Change microbial inactivation rate by 90%
• D. Change microbial inactivation rate by 10%

Hint:

Remember the terms:
- D-value: Time needed for a 90% (1-log) reduction in the microbial population.
- z-value: Temperature change needed for a 90% (1-log) change in the D-value.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Decimal reduction time, also known as the D-value, is a key parameter used in food sterilization and thermal processing.
It measures the heat resistance of a specific microorganism at a constant temperature.

Step 2: Detailed Explanation:
Let us analyze the definition and meaning of the D-value:
- During thermal processing, the destruction of microorganisms follows first-order kinetics, meaning the rate of death is proportional to the concentration of living cells.
- The D-value is defined as the heating time (in minutes) required at a specific temperature to reduce the microbial population by 90%.
- For example, if a population of \(10^6\) cells is heated for one D-value duration, the surviving population will be \(10^5\) cells.
- A 90% reduction in population corresponds to a one-log reduction (since \(\log_{10}(10^6) - \log_{10}(10^5) = 6 - 5 = 1\)).
Let us review the options:
- Option (A) describes the \(z\)-value, which is the temperature change required to alter the D-value by a factor of 10.
- Option (B) correctly describes the D-value (Decimal reduction time).
- Options (C) and (D) are incorrect because the D-value relates to the reduction of the actual microbial population, not the inactivation rate itself.

Step 3: Final Answer:
The correct option is (B).