Mold on Butter – Is it Safe to Eat?

Sometimes butter can get moldy when you leave it out in a warm and humid environment. 

You must be wondering: Is moldy butter safe to eat? The simple answer is no. Butter is soft and becomes prone to toxins if there is mold. According to the FDA, eating moldy butter is unsafe as the toxins may hurt the immune system. So, if you notice visible mold on butter, we recommend throwing it away to avoid serious health problems.

Let’s explore the reasons for mold growth on butter and how to store butter to preserve its freshness.  

Table of Contents

Why Does Butter Go Moldy?

Butter does grow mold but not as quickly as other dairy products. The high-fat content in butter means that it is at risk of growing moldy or rancid. Other aspects such as unclean utensils, heat, light, and oxygen also add to this risk. 


Oxidation is a natural process in which food exposed to oxygen for extended periods may deteriorate. 

You cannot prevent oxidation, but you can slow down the process by selecting a proper storage method.

Exposure to Light and Air

Light and air are the major factors that add to the risk of mold growth in butter. Not storing your butter in an airtight container allows these elements to damage it.

Unsalted Butter at Room Temperature

If your recipe calls for unsalted butter, then you may leave it on the countertop for a few hours before baking. However, if you are not going to use it anytime soon, keep it in the fridge.

Unsalted butter is more prone to mold formation at room temperature. In comparison, salted butter contains salt, which protects it from any fungal growth.

Extreme Heat 

Exposure to heat promotes mold growth in soft foods like butter. Keeping your butter container near the oven or in a warm environment may also trigger mold growth.      

A temperature that surpasses 70°F in your kitchen is not suitable for butter storage. 

Contaminated Utensils

Make sure you use clean utensils to spread butter on any of your food. The contaminated utensils may contain other food particles that infect your butter with netty mold.

What Happens If You Eat Moldy Butter?

How To Know If Butter Has Gone Bad?

Now that you know why butter goes moldy, you can easily tell your butter has spoiled. 

For example, if you have kept the butter out of the fridge for two days, is it still edible?

Let’s find out by analyzing a few things mentioned below:

  • Smell: Smell is the first thing that helps you to know if your butter is spoiled or not. Rancid or moldy butter has an unbearable sour smell which you may note immediately. It is pretty similar to blue cheese
  • Mold: If you can see mold on butter’s surface, you don’t need to cut down the moldy part. Throw out the whole stick. 
  • Texture: Fresh butter has a pale yellow color. But if your butter is rancid or has gone bad, its texture or color will change to intense yellow. So, it would be best if you did not use it. 
  • Taste: Usually, sour-smelling butter will have a sour or rancid taste. You can check this out by slightly tasting your butter. And if the taste is unpleasant, throw it out. Note: Tasting won’t harm you in any way.  

Can You Use Expired Butter? 

If your butter is past its ‘best-by’ date, check for any changes in its texture, smell, and color. When butter goes bad, it smells rancid and has slight color changes. Expired or moldy butter also tastes sour. You can safely taste it to check if it has gone bad, but eating a lot of expired or moldy butter will make you sick.

That said, keep in mind that under the best storage conditions, butter may not go bad or moldy immediately on that date. It may stay safe to eat for days, even months. You need to look at the spoilage signs to check if you should throw the stick out.

Expired or Moldy Butter

Like most dairy products, butter doesn’t go bad without noticeable signs. So, if your butter looks and smells okay, it probably is.

The smell of rancid or moldy butter is its biggest giveaway. Even if you miss the smell, you will taste the difference in just one bite because of the mold.

There are some other visible signs as well. Butter can change its color when it goes past its expiration date, though it usually happens when it catches mold. It is rare, but butter can develop mold.

Mold will be quite visible on the butter and usually results from cross-contamination.  

Shelf Life of Butter

Dairy products usually have a short life – but not butter. Butter is the most resilient of all the dairy products. Even cheese becomes moldy much earlier than butter.

If you have packaged butter, the ‘best-by’ date printed on the pack is usually between 3 and 6 months after the manufacturing date.  USDA also recommends using up all the butter by that time.

However, if refrigerated properly, an unopened can only last for about a month past the expiry date. If frozen, it may last six to ten months past that printed date.

If the pack of butter is open, you can put it in an airtight container and extend its shelf life. Store it in an open container, and the butter will only last one or two weeks.

Most of you must have noticed that your butter lasts longer than that. That is because people usually have the salted butter in their homes. The salt added for taste also works as a preservative so that it lasts longer. It will stay good for around three months after the ‘best-by’ date stamped on the package.

Bear in mind that these numbers are simply an estimate of how long butter is useable past the ‘best-by’ date. If the storage conditions aren’t great, it might even go rancid and moldy before the expiry date.

What About Butter Poisoning?

There hasn’t ever been case of food poisoning from butter. It may be because most recipes call for a small proportion of it. No one eats an entire bar of butter.

Although some experts suggest that eating rancid butter can reduce your Vitamin E and B stores, this study is almost half a century old.

That said, keep in mind that butter can go rancid because of its high-fat content. And fat goes rancid as it oxides. Exposure to air, heat, and light can make fat go bad. That is why it is important to store your butter away from these elements.

Additional Tips for Storing Butter

Some types of butter should be kept in your fridge, but it’s also fine to keep salted butter on the counter.

Here are some tips you can follow to make sure your salted butter stays fresh when stored at room temperature:

  • Only keep a small amount out on your counter. Store the rest in your fridge or freezer for future use.
  • Protect butter from light by using a closed kitchen cabinet or an opaque container.
  • Store butter in an airtight container.
  • Keep butter away from direct sunlight, the stove or any other heat sources.
  • Store it out of the fridge only if the room temperature is below 70–77°F (21–25°C).

There are plenty of dishes specifically designed to meet these needs, but an opaque storage container also works well.

How To Store Butter?

Here are some of the best ways to store your butter ideally:

Refrigerate It

It isn;t necessary to store your butter in the fridge to protect it from mold growth. However, refrigeration can significantly enhance the shelf life and freshness of butter. 

If you have bought a large quantity of butter, then freezing is also a great option. Butter can stay fresh for about 6 to 10 months in the freezer. 

To freeze the butter correctly, wrap it in aluminum foil (you may cut the butter into desired pieces and then wrap it). Then place this covered butter in a plastic freezer bag. It will protect the butter from freezer burn and won’t take on the smell of other foods. 

When you want to use the butter, take it out from the freezer. And put it in the fridge or at room temperature to thaw. 

Keep It At Room Temperature

Storing your butter at room temperature is completely fine. It keeps the butter creamy and soft, and hence spreading it on foods becomes easy. 

According to the USDA, you should consume the butter left out at room temperature within one to two days. Only take out the amount of butter you need and store the rest in the fridge. The flavor will start to turn sour if you keep the butter out for many days.

Keep in mind that butter comes in two varieties, salted or unsalted. If you are using salted butter, then you can store it at room temperature for longer. 

Choosing The Right Storage Container

If you plan to keep your butter at room temperature, then choose the right container for it. A correct container protects the butter from oxidation and retains its freshness. So the butter lasts longer, even outside of the fridge.

  • Butter crock: A butter crock (French butter keeper or butter bell) contains an inner pot that holds the butter. The pot is submerged in the water, and hence this technique ensures an air-tight seal. 
  • Butter dish: It perfectly stores the butter for a short time and protects it against light and air. These dishes come in various designs and sizes.  
  • Plastic food container: It is a budget-friendly option to preserve the butter. However, it would be best if you keep it air-tight.

The Bottom Line

Keeping butter in your fridge can maximize freshness while leaving it on your counter keeps it soft for immediate use. It’s fine to keep salted butter out of the fridge, as long as it’s kept away from heat, light, and air. These methods can help your butter stay fresh longer. But, if you notice mold on your butter, you should throw it out to avoid getting sick.


Can mold on butter make you sick?

No, it will not make you sick. The worst-case would vomit or an awful smell. However, it is typically rare. A little mold does not affect a healthy person.

What makes some butter harder than others?

Research shows various types of fatty acids (which make the fat in butter) are present in different kinds of butter. Therefore, the hardness of butter varies.

Can you bake with rancid butter?

Although it has a shallow safety risk, you can use rancid butter in your recipes. But it will affect the taste and quality of your food. So, buy fresh butter. 

How long does it take butter to go rancid?

It takes almost two weeks for the butter to go rancid. If you store butter at room temperature, make sure you use an accurate container. 

Is it OK to put softened butter back in the fridge?

Yes, it should be OK. According to USDA, you should always refrigerate the butter and only soften the required amount “10 to 15 minutes” before use. 

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