Correct Answer - Option 2 : D-value
The D value is a measure of the heat resistance of a microorganism. It is the time in minutes at a given temperature required to destroy 1 log cycle (90%) of the target microorganism.
D-Value (Decimal Reduction Value):
It is the time required at temperature T to reduce a Specific microbial population by 90% or by a factor of 10.
Z-Value:
It is the number of degrees of temperature change necessary to change the D-Value by a Factor of 10.
F-Value:
1. The F value for a process is the number of minutes required to kill a known population of microorganisms in a given food under specified conditions.
2. This F value is usually set at 12 D values to give a theoretical 12 log cycle reduction of the most heat-resistant species of mesophilic spores in a can of food.
Difference between D-Value and Z-Value
| BASIS |
D Value |
Z Value |
| Definition |
It is the time required to reduce 90% of a specific bacterial population in a given medium at a given temperature. |
It is the temperature change that is required to achieve a tenfold reduction in the D-value. |
| Unit |
Minutes |
Celsius |
| Measurement |
Time taken |
Temperature change |
Thermal Death Time (TDT)
- TDT is the amount of time that is necessary to kill a specific number of microbes at a specific temperature.
- This value is obtained by keeping temperature constant and measuring the time necessary to kill the number of cells specified.
