Question

Thermal death time (TDT) curve is between .......

• A. Time v/s temperature
• B. Temperature v/s log (time)
• C. Time v/s log (number of survivors)
• D. Temperature v/s Time

Hint:

To keep these curves distinct:
- Survivor Curve (D-value): Log (Survivors) v/s Time (at a constant temperature).
- TDT Curve (z-value): Log (Time) v/s Temperature (varying temperatures).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Thermal death time (TDT) is the time required to completely destroy a specific microbial population at a constant temperature under defined conditions.
It is used to calculate the thermal processing times required for canning and commercial sterilization.

Step 2: Detailed Explation:
Thermal microbial destruction follows first-order reaction kinetics.
A semi-logarithmic plot of the time required for complete microbial ictivation at different processing temperatures is called the Thermal Death Time (TDT) curve.
In a TDT curve:
- The linear horizontal axis (x-axis) represents the processing temperature in degrees Celsius (\( ^\circ\text{C} \)) or Fahrenheit (\( ^\circ\text{F} \)).
- The logarithmic vertical axis (y-axis) represents the heating time (TDT) in minutes on a logarithmic scale.
This plot yields a straight line with a negative slope.
The slope of this line is used to calculate the \( z \)-value, which is defined as the temperature increase required to cause a tenfold change in the thermal death time.
For comparison, a plot of the log of the number of survivors versus heating time at a constant temperature is called the Survivor Curve (used to determine the \( D \)-value).

Step 3: Fil Answer
Therefore, the thermal death time (TDT) curve represents the relationship between Temperature and the logarithm of heating Time.