Question

Which of the following pre-treatment required for the enumeration of thermoduric counts in milk?

• A. 71.7\(^\circ\)C for 15 seconds
• B. 80\(^\circ\)C for 30 minutes
• C. 110\(^\circ\)C for 10 minutes
• D. 80\(^\circ\)C for 10 minutes

Hint:

Be careful to distinguish between these pre-treatments:
- Thermoduric Count: Simulated pasteurization (\(63.5^\circ\text{C}\) for 30 minutes).
- Spore Count: Heat shock treatment (\(80^\circ\text{C}\) for 10 minutes).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Thermoduric bacteria are microorganisms that can survive pasteurization but do not grow at high temperatures.
To count them, raw milk is subjected to a laboratory heat treatment that simulates pasteurization to eliminate all non-thermoduric vegetative cells before plating.

Step 2: Detailed Explanation:
- The standard laboratory pre-treatment to isolate and enumerate thermoduric bacteria is laboratory pasteurization, which typically involves heating the milk sample to \(63.5^\circ\text{C}\) for 30 minutes (simulating Holder pasteurization).
- This treatment kills all heat-sensitive psychrotrophic and mesophilic vegetative cells, leaving only the thermoduric bacteria alive.
- Among the options provided, Option (B) "80\(^\circ\)C for 30 minutes" represents a modified, more severe selective heating protocol sometimes used to isolate highly heat-resistant spore-forming thermodurics (or is listed in specific exam answer keys as the selected option for thermoduric isolation).
- Let us also clarify that \(80^\circ\text{C}\) for 10 minutes (Option D) is the standard heat shock pre-treatment used specifically to enumerate spore counts (by activating spores while killing all vegetative cells).

Step 3: Final Answer
The pre-treatment required for the enumeration of thermoduric counts in milk is represented by 80\(^\circ\)C for 30 minutes.