Why milk turn sour?

Milk turns sour because of the lactic acid bacteria present in it. These bacteria convert the lactose (sugar) present in milk into lactic acid, which gives milk its sour taste and smell. Lactic acid bacteria are commonly found in the environment, and they can easily contaminate milk if it is not handled properly.

The growth of lactic acid bacteria is promoted by warm temperatures, so it is important to keep milk refrigerated to slow down the process of spoilage. Milk can also be pasteurized to kill off harmful bacteria, including lactic acid bacteria. Pasteurized milk has a longer shelf life than unpasteurized milk, but it can still eventually turn sour if it is not stored properly.

Here are some tips to help prevent milk from turning sour:

* Keep milk refrigerated at a temperature of 40 degrees Fahrenheit or below.

* Purchase milk that is fresh and has a sell-by date that is several days in the future.

* Avoid leaving milk out at room temperature for longer than two hours.

* Do not open the milk carton until you are ready to use it.

* Wipe the rim of the milk carton clean before replacing the cap.

* Store milk in the coldest part of the refrigerator, which is usually the back.

By following these tips, you can help keep milk fresh and prevent it from turning sour.