Why Does Milk Expire So Fast? Find Out

Milk has everything but long life. It’s a natural urge to buy more milk when you are at the grocery store. The reality that you can’t keep milk for long sets in once you’re back home. I bet you’ve wondered what makes milk expire so fast.

And to think that milk goes through pasteurization to kill bacteria. Yet, milk still goes bad despite its expiration date, especially if you did not refrigerate it. In simple words, milk expires fast when it experiences a rapid temperature drop.

Then, how long can milk last? How long can you preserve it? How can you be sure the milk has gone bad? Continue reading to see the answers to your questions.

Why does milk expire so fast?

Milk expires fast when there is a rapid and continuous drop in temperature.

The USDA advises that milk should be kept at 40°F in the refrigerator. At room temperature, milk should not go below 35°F.

When you expose milk to rapid and continuous temperature fluctuations, it becomes habitable for bacteria like lactobacilli and lactococci.

The activities of these bacteria in milk break down lactose into glucose, galactose, and lactic acid. Consequently, lactic acid makes the milk curdle and triggers mold growth.

Why does almond milk expire so fast?

Homemade almond milk expires fast; it expires faster than a store-bought variety.

Store-bought almond milk goes through pasteurization to kill bacteria and make it shelf-stable. On the other hand, a homemade version does not go through this process.

Any bacterial contamination that occurs during the making process remains in the milk, and it is transferred altogether into an airtight container and stored.

Moreover, the milk is stored with more oxygen which promotes bacterial growth and action in the milk.

Why does chocolate milk expire so fast?

Chocolate milk expires so fast because of its high sugar content.

Naturally, milk contains lactose. When it also contains sugar, lactose converts the sugar into lactic acid.

A higher sugar content equals a higher amount of lactic acid. Consequently, the faster the rate of spoilage.

What is the shelf life of milk?

The shelf life of milk is dependent on factors like the method of preparation, the type of milk, and the brand.

Generally, you can expect a carton of milk to last 5 to 10 days under proper storage conditions.

An opened carton of any type of milk lasts 5 to 7 days in the refrigerator after the printed date.

In the refrigerator, an unopened carton of reduced-fat and skim milk will last 7 days. Non-fat and lactose-free milk last 7 to 10 days, while whole milk lasts 5 to 7 days after the printed date.

How do you know milk has expired?

Carefully examine the milk for signs of spoilage. These are some of the signs to watch out for:

  • Lumps at the bottom of the milk
  • A sour or pungent smell
  • A dirty, grimy, or yellow color
  • Also, if the milk is gooey after microwaving, it has expired
  • Do the acidity test. Put a teaspoon of baking soda in a small bowl and pour milk over it. If bubbles form on the baking soda, the milk has gone sour and acidic. Baking soda does not bubble with fresh milk

Will you get sick from drinking expired milk?

On a one-time occurrence, you may not get sick after drinking expired milk.

But, you may experience signs of food poisoning when you consume expired milk in large amounts.

How to preserve milk

  • If milk is not shelf stable, do not leave it out of the refrigerator for more than 2 hours
  • Pasteurize raw milk to preserve it longer and prevent spoilage
  • You can also turn fresh milk into canned milk. While you may not like to drink this milk because of changes in its color, it’s perfect for cooking and making cheese
  • Additionally, you can dehydrate fresh milk into powder form
  • You can also condense fresh milk to preserve it
  • Keep opened cartons of milk in the refrigerator or freezer
  • Keep unopened milk frozen if you need it around for a longer period
  • Keep the temperature in the refrigerator between 38°F to 40°F
  • Also, do not keep cartons of milk on the refrigerator door. Instead, keep them on the refrigerator shelves where it’s colder
  • Do not expose milk to sunlight
  • The best way to store milk is in the containers it came in and always keep them tightly covered
  • Save yourself from contamination by not pouring milk from a used cup back into the carton or container
  • Most importantly, buy milk that has a longer shelf life from the day of purchase


Does milk expire faster when it’s opened?

Yes and no.

If you store an open carton of milk properly, it should not expire quickly except if it’s way past its printed date. In contrast, if you don’t store an open carton of milk properly, it’ll go bad faster than you expected.

Which milk lasts longer?

Milk that has gone through ultrapasteurization will last longer than regular milk. Ultrapasteurized milk lasts three times longer than regular short-time pasteurization.

Ultrapasteurization is a process of heating milk to 280°F and cooling it rapidly. But just like the High-temperature short-time (HTST) pasteurization, it also makes sure that milk is 99.9% bacteria-free.

What milk spoils the fastest?

Skim milk spoils the fastest among all the types of milk.

This is because of its very low-fat content. Milk with a higher fat content lasts longer.

Why did milk go bad so fast in the fridge?

Where you store a carton of milk in the refrigerator influences how long it lasts. Keeping milk in the refrigerator’s door can make it go bad quickly.

When you open the door, the temperature drops rapidly from 40°F to room temperature.

Temperature fluctuation fosters bacterial growth and action and triggers spoilage. Also, keeping milk longer than 7 days in the refrigerator can cause spoilage.

Can milk go bad in the freezer?


Thawing and refreezing milk will make it unappetizing with time. Moreover, thawing milk at room temperature increases the risk of bacterial growth. It is best to not refreeze thawed milk.

In addition, when you freeze milk without covering it properly, it could get contaminated and spoil eventually.


If you do not refrigerate or freeze that open carton of milk, you shouldn’t expect to keep it for long.

Factors like temperature fluctuations, bacterial growth and action, storage conditions, and expiration date impact the shelf life of milk.

If you want to enjoy milk, it starts with the day you go shopping. Buy milk that has a longer shelf life.

Also, store unopened cartons of milk properly. Keep open cartons of milk in the coldest area in the refrigerator. Most importantly, discard milk once you notice any signs of spoilage.

Thanks for reading.

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