Pasteurized milk is tested by
**Core Concept**
Pasteurization is a process that kills harmful bacteria in milk by heating it to a specific temperature for a certain period. This method is widely used to prevent the spread of diseases caused by bacterial contamination in milk and dairy products.
**Why the Correct Answer is Right**
The correct method for testing pasteurized milk involves checking for the presence of living bacteria. Pasteurization is effective in killing most bacteria, but some bacteria like Bacillus stearothermophilus are more resistant to heat. To ensure that milk has been properly pasteurized, it is tested for the absence of these heat-resistant bacteria. This is typically done by incubating a sample of milk at a suitable temperature and observing for the growth of bacteria.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the type of bacteria being tested for. Pasteurization is effective in killing most bacteria, but some bacteria like Bacillus stearothermophilus are more resistant to heat.
* **Option B:** This option is incorrect because it does not provide a specific method for testing the pasteurization of milk.
* **Option C:** This option is incorrect because it does not specify the type of test being used to determine the pasteurization status of milk.
**Clinical Pearl / High-Yield Fact**
To ensure the quality and safety of pasteurized milk, it is essential to test for the presence of heat-resistant bacteria like Bacillus stearothermophilus. This can be done using a standard plate count method or by using a pasteurization test kit.
**Correct Answer:** D