Question

The \(D_{\text{r}}\) value of Clostridium botulinum type A and B is -

• A. 0.21
• B. 0.32
• C. 0.35
• D. 0.41

Hint:

Remember the core constants of the "Botulinum Cook":
- Reference temperature = \(121.1^\circ\text{C}\) (\(250^\circ\text{F}\))
- \(D_{\text{r}}\) = \(0.21\text{ minutes}\)
- \(z\)-value = \(10^\circ\text{C}\) (\(18^\circ\text{F}\))
- Target lethality (\(F_o\)) = \(2.52\text{ minutes}\) (often rounded to \(3.0\text{ minutes}\))

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The decimal reduction time (\(D\)-value) is the heating time required at a constant temperature to kill \(90\%\) (or 1 log cycle) of a specific microbial population.
The reference \(D\)-value at \(121.1^\circ\text{C}\) (\(250^\circ\text{F}\)) is designated as the \(D_{\text{r}}\) value.

Step 2: Detailed Explanation:
The spores of Clostridium botulinum types A and B are the most heat-resistant strains of pathogenic bacteria found in low-acid foods.
In industrial canning calculations, the internationally accepted reference value for the destruction of these highly resistant spores is:
\[ D_{\text{r}} = D_{121.1^\circ\text{C}} = 0.21\text{ minutes} \quad (\approx 12.6\text{ seconds}) \]
Using this value, the minimum time required for a \(12\text{-D}\) sterilization process (the botulinum cook) is calculated as:
\[ F_o = 12 \times D_{\text{r}} = 12 \times 0.21\text{ minutes} = 2.52\text{ minutes} \]

Step 3: Final Answer:
The \(D_{\text{r}}\) value is 0.21 minutes, which corresponds to option (A).