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How Long Can Milk Sit Out?

Posted in Food Safety on May 30, 2022

Updated April 9, 2024

Many wonder, how long can milk withstand being left out before it spoils? Whether due to absentmindedness or simply a curiosity about the science behind it, many wonder about the factors influencing milk’s shelf life outside the refrigerator.

How Long Can You Leave Milk Out of the Fridge?

Milk can be left out for approximately two hours, however, if the temperature in the room reaches 90° F, then milk can only sit out for one hour. Various factors can influence how long your milk stays fresh. Our food hosts a multitude of microbes. Some are helpful, aiding in digestion, while others pose risks, causing foodborne illnesses. Dairy products are particularly prone to contamination as harmful bacteria thrive in them. Among the most concerning are E. coli, Salmonella, Campylobacter, and Listeria, all capable of inducing severe food poisoning symptoms, sometimes necessitating hospitalization.

What Happens to Milk When It Is Left Out?

When milk is left unrefrigerated for an extended period, bacteria will begin to grow. The lactose in the milk becomes fermented by bacteria at room temperature and turns into lactic acid. A high amount of lactic acid in milk means a high amount of hydrogen ions, which causes a sour taste with a low pH value. When there is low pH, the structure of proteins in the milk, such as casein, will change, causing the milk to curdle. After the bacterial reaction occurs, there will be a yellowish liquid left behind called whey.

How Milk Should be Stored

Here are some tips for storing milk to keep it from spoiling quickly:

  • Place milk in the fridge as soon as possible after purchase unless it is shelf-stable.
  • Make sure the temperature of your refrigerator stays between 38°F (3°C) and 40°F (4°C).
  • Store milk on an interior shelf in your fridge rather than on a shelf in the door
  • Always tightly seal after each use and quickly return it to the refrigerator.

Milk can stay good for several days after the sell-by or best-by date when properly stored.

How Do You Tell if Milk is Spoiled?

There are several ways to tell if milk has spoiled:

Change in Smell
One of the first signs that milk has expired is a change in smell. The lactic acid build-up from bacteria will create a distinct sour odor.

Change in Taste
If you drink milk and it has a sour taste, it is safer to discard it. Fresh milk should have a creamy and sweet taste.

Change in Texture
As the milk begins to curdle, it will look thicker and possibly lumpy.

Change in Color
With enough time, spoiled milk will also change color from pearly white. If you notice anything different about the color, it is a sign it is no longer good.

Sell-By Date has Passed
The sell-by date is not necessarily the expiration date but can be used as a barometer for how long the milk may possibly be good for.

  • Lactose-free milk should be good for 7-10 days past the printed date.
  • Non-fat milk should be good 7-10 days past the printed date.
  • Reduced-fat milk should be good 7 days past the printed date.
  • Whole milk should be good 5-7 days past the printed date.

What Happens if You Drink Spoiled Milk?

A small sip of spoiled milk likely is not a cause for concern. However, if you ingest a moderate or large quantity of spoiled milk, it can take a toll on your gastrointestinal tract. The overgrowth of bacteria may cause a mild case of food poisoning which can present with symptoms of abdominal pain, nausea, vomiting, and diarrhea. If you or a loved one became sick from drinking contaminated milk that was not properly handled by a restaurant or by the manufacturer, you may be able to file a product liability claim. To learn more, speak with an experienced food safety lawyer.