How To: The Best Way To Tell If Buttermilk Is Bad

Buttermilk is such a versatile ingredient. It is used frequently in baking, but it can also be used to cook savory meals too.

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Given that it is not an ingredient that you will use every day, you may notice that you end up throwing away the leftover buttermilk.

If you have had buttermilk for a long period, you may be unsure whether it is still safe to use. This is completely normal and as it is a dairy product, you do not want to end up using bad buttermilk.

Not only will it taste foul, but it could also make you ill too.

The question you may be asking, is how to tell if buttermilk has gone bad? Does buttermilk go bad? And how long does buttermilk last?

How To Tell If Buttermilk Is Bad The Best Way

Knowing this is so useful and will help you to learn when the buttermilk is still safe to consume. It may also help to stop you from unnecessarily throwing out buttermilk that is still safe to use too!

In this article, we will be churning over some methods of how you can tell if buttermilk is bad. We will be discussing how successful each way is and letting you know the best, foolproof method of finding out. 

In addition to this, we will also be providing you with some tips on how to extend the life of buttermilk too. We hope that you will find this article helpful!

What Is Buttermilk?

You may be surprised by how many people do not know what buttermilk is. It is something that many of us will use for cooking quite often, but have never actually considered what it is, and how it is made. 

Traditional buttermilk can be created in two different ways. The original, homemade way to create buttermilk is through using the liquid leftover once the homemade butter has been churned.

This liquid is watery and not fatty. The cultures that are in this liquid increase after a few hours when left at room temperature. It is these cultures that improve the taste of the buttermilk overall. 

When it comes to creating mass amounts of buttermilk a different method is used. More commonly, buttermilk is created by using cultured milk that has a similar consistency to thick yogurt

The biggest difference from homemade buttermilk is that the buttermilk is no longer a by-product of milk. Instead, the cultures are placed into the milk and this creates the buttermilk you are likely familiar with. The cultures used are lactic acid bacteria, which are completely harmless. 

Unlike the original way to create buttermilk where it contained virtually no fat, buttermilk today does. You have likely noticed that buttermilk can be purchased with a range of different fat contents from full fat to skimmed. This is great because it will suit a wide variety of tastes and recipes. 

The majority of recipes that contain buttermilk will be referring to store-bought buttermilk instead of homemade buttermilk. Store-bought buttermilk tends to be higher in its acidity and thicker than homemade buttermilk. This is why it is the preferred buttermilk to use in recipes. It is also known for its slightly tangy taste. 

How To Tell If Buttermilk Is Bad

With buttermilk being a dairy product, there are a few telltale signs of it being bad.

Sometimes with dairy products, you can just tell when they are not safe to use. Here are some foolproof ways to tell if your buttermilk has gone bad.


Often with buttermilk as with other dairy products, you can tell that it has gone bad just by looking at it.

When buttermilk has turned bad it will look slightly different from how it was when you first purchased it. Usually, it will be a slightly different color. 

If the buttermilk has been sitting in your fridge for a long time, then it may begin to grow mold. If there is mold in or on the top of the buttermilk this is a clear sign that it is not safe for consumption. 

If any mold is visible, regardless of if the buttermilk is still in date you will need to throw it away as soon as possible. Using moldy buttermilk will severely increase your chances of catching foodborne illnesses.


One of the easiest ways to tell if buttermilk has gone bad is by its smell. In comparison to milk, buttermilk does have a distinct smell, this does not necessarily mean that it is bad, however.

It is normal for buttermilk to have a tangy and stronger smell than milk.

You will know if buttermilk has gone bad if it smells sour. If the buttermilk has been bad for a few days, then it is likely that the sour smell will be pungent and will make you want to pour the buttermilk away instantly. 

However, buttermilk that has just turned bad can be challenging to detect with smell straight away. While this is a good method, it is not always successful. 


Buttermilk that is safe to consume does have a tangy taste. It is not entirely smooth like milk and does have a stronger taste. This is perfectly normal and nothing to worry about. Buttermilk has a distinctive creamy, buttery taste.

If the buttermilk does not have this creamy, buttery taste it is likely bad. In addition to this, it can be accompanied by a sour taste. Buttermilk should not taste sour in any way, if it does, it should not be used. 


The texture of buttermilk is usually a big giveaway if it has gone bad.

Rancid buttermilk acts in a similar way to milk. Instead of being its normal consistency, it will develop a thick and often chunky texture. It will not pour easily and will have a cottage cheese type consistency.

Once buttermilk has developed this thick and chunky texture it is no longer safe to use and will need to be thrown away.

Buttermilk does tend to have small lumps so do not panic if you find them in your newly opened carton. These will naturally separate when you use the buttermilk. The large lumps found in bad buttermilk will not. 

Expiry Date

Before you use buttermilk it is always important to check the expiry date. As buttermilk is a dairy product, it is usually bought fresh.

Given this, it will not last as long as canned or dried food. Given this, you should plan when you are going to use the buttermilk accordingly. 

If the buttermilk has passed its expiration date, it should be thrown away. While it may look and smell okay, fresh food has an expiry date for a reason. If you consume food past its expiration date it is more likely that you will develop a foodborne illness. 

In most cases, if you are using the buttermilk before the expiry date then it will be absolutely fine to use. However, on some occasions, especially if your buttermilk has not been stored correctly, it can go off quicker.

Given this, we would always recommend carrying out the other checks instead of relying on the expiry date alone. 

How Long Should Buttermilk Last?

How long the buttermilk will last will depend on the buttermilk you have purchased. Every carton of buttermilk will have its expiration date.

Although the expiration date may be quite a while away, the date you will need to use it does change slightly once the buttermilk has been opened.

This is because the buttermilk is sealed from air and bacteria when it has not been opened. As soon as you open it, the product will begin to slowly deteriorate.

It is worth noting that there will be two different dates on the majority of buttermilk cartons. These two dates are the sell-by date and the expiry date.

The sell-by date is when the store will need to sell it by. This date is typically shorter than the expiry date. The expiry date is when you will need to use the product by.

The product is still safe to consume after the sell-by date if it has not gone bad. It is not safe to use after the expiry date, however. 

Buttermilk should always be kept in your refrigerator. If you store it in your cupboard it will go bad quickly. This is because it needs to be kept cold.

In addition to this, if you mix any other food or liquid with the buttermilk, this can affect how long it will last. 

Why Does Buttermilk Go Bad?

As with any type of food, buttermilk has an expiration date. No food can last forever and as a result, the buttermilk will eventually go bad.

The good thing about buttermilk is that it contains a lot of lactic acids. This lactic acid helps to preserve other buttermilk for a period. 

However, after around two weeks, bacteria will start to grow and multiply in the buttermilk. It is this bacteria that causes it to go bad. The bacteria causes the acid levels in the buttermilk to rise which then ferments it. 

How To Keep Buttermilk Fresh For As Long As Possible

Keeping all of this in mind, there are a few different ways that you can help to prolong the shelf life of your buttermilk.

Storing The Buttermilk correctly while spoiling is eventually inevitable, correctly storing your buttermilk helps to prolong its shelf life. 

As mentioned above, buttermilk should always be stored in the refrigerator. If you leave it out of the refrigerator for too long the bacteria will quickly multiply and cause it to go bad quicker. 

Expiration Date

If you are not planning to use the buttermilk straight away, we would recommend purchasing a carton with the longest expiration date.

In addition to this, you could purchase the buttermilk on the day you are planning to use it, instead of with your weekly grocery shop.

Keeping The Buttermilk Clean

We would recommend that you do not mix anything with your buttermilk as this can affect its shelf life.

Always ensure you have clean hands while pouring your buttermilk to avoid adding any bacteria into it.

Can You Freeze Buttermilk?

One way that you can make your buttermilk last longer is by freezing it. Buttermilk can be safely frozen and defrosted. This is great if you only usually use part of the carton. It extends its shelf life and stops it from going to waste.

To freeze your buttermilk you will want to empty it out of the carton that you purchased it in and pour it into an airtight container.

Place the airtight container into the freezer. Make a note of the day it was frozen, this will help you to remember when it needs to be used.

Buttermilk can be stored in the freezer for 1-2 months. It is worth noting that freezing the buttermilk will change its consistency. After it has been defrosted it will likely separate and contain larger lumps.

Given this, you should avoid drinking it. Thawed buttermilk should only be used for recipes and meals that will be thoroughly cooked. 

Powdered Buttermilk

If you find that your buttermilk is always going to waste, it is worth looking into powdered buttermilk. This is a great solution to your problem.

As it is in powdered form it has a much longer shelf life. In addition to this, it can be stored in your cupboard instead of the refrigerator.

Powdered buttermilk is a great option for use in baking, but it cannot be drunk. As with any powdered food, it will not have the same consistency or quality as fresh buttermilk, but it is a good solution if you want it to last for a longer period. 


We hope that this article helped you with any questions that you may have had about buttermilk.

As you can see, there are many ways in which you can tell if buttermilk is bad. By using all of these techniques together you will gain a good idea of if it is safe to use. 

Always remember that if you keep your buttermilk in the refrigerator and at the correct temperature it should stay good for a long time.

If you find yourself still throwing away a lot of buttermilk after trying our suggestions, it is always worth giving powdered buttermilk a try instead! I tend to stay away from sour milk myself, but I do find powdered milk helpful in the kitchen as well as cultured buttermilk and almond milk.

Though I tend to throw away opened buttermilk quickly. I'm always worried it will turn into spoiled buttermilk. Buttermilk pancakes are my favorite recipe, though who can say no to buttermilk biscuits.

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Cassie brings decades of experience to the Kitchen Community. She is a noted chef and avid gardener. Her new book "Healthy Eating Through the Garden" will be released shortly. When not writing or speaking about food and gardens Cassie can be found puttering around farmer's markets and greenhouses looking for the next great idea.
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