Blue Cheese Mold: Safe To Eat Moldy Blue Cheese Or Throw It Out?

Blue cheeses are famous for their rich, tangy tastes and smooth creamy textures. They are also famous for being moldly, but which are safe to eat and which should you avoid? How can you tell if your cheese has gone bad, and how can you stop your blue cheese from going moldyOpens in a new tab. prematurely?

In this article, we will be answering all these questions and more, so for all you need to know about blue cheese mold, keep reading.

blue cheese mold

Is blue cheese a type of mold?

Blue cheese is not mold in itself, however, a strain is introduced to the cheese in order to create the dark blue “veining” that the cheeses are famous for.

Blue cheeses are most commonly made from cow, sheep, or goat’s milk. After the whey and curd are separated, Penicillium Roqeforti is introduced directly into the curd, which is formed into wheels and left to age.

In order for the deep blue “veining” throughout the cheese to occur, rods or spikes are inserted into the center of the cheese which gives the fungi the oxygen it requires to grow.

So, an aged blue is not completely made of fungi, but it certainly has it within it and on some cheeses (such as Brie), a strain is applied to the outer layers to create its characteristic rind.

Why does blue cheese get moldy?

Aside from the fungi that are purposely added, other strains of fungi can grow on blue cheese that is potentially harmful to humans and animals.

As long as fungi have a source of nutrients, an adequate level of moisture, and their preferred temperature range, they will be able to flourish. Let’s take a closer look into some of the reasons it forms on blue cheese.


Many blue cheeses are semi-soft, such as Brie and Roquefort. This means their water content is higher than hard cheeses such as cheddar, so they will often grow molds more quickly.

As cheese “breathes”, they release some of its moisture, and if stored incorrectly, this can condensate and become an excellent source of hydration for fungi. High refrigerator humidity levels will also increase the likelihood of condensation and pooling of liquids around the surface of the cheese.


The nutrients of course come from within the cheese itself, as it contains all the fats, carbohydrates, proteins, and minerals that it needs for sustenance. It can access these nutrients by releasing enzymes that break down the cheese, which can then be absorbed.


The ideal temperature range for many fungi to grow at their fastest rate is between 60-80 degrees Fahrenheit, however, the strains that are likely to grow on cheeses often grow relatively well even at refrigerated temperatures. This means that even slight increases can rapidly speed up the rate of growth.

What kinds of mold grows on blue cheese?

The strain that is purposely introduced to blue cheese is penicillium roqueforti. This is generally harmless to humans and creates the characteristic taste and texture of many blue cheeses.

However, other strains can grow if the conditions the cheese is stored in are incorrect, many of which can be harmful to both humans and animals.

Other potential strains can include:

  • Aspergillus Niger
  • Cladosporium
  • Monilla
  • Mucor
  • Fusarium

Is the mold dangerous?

As a general rule, the fungi that give the cheeses their characteristic blue color is penicillium roqueforti, and is not hazardous to humans or animals if ingested or its spores inhaled. However, for people with suppressed immune systems or those with allergies, blue cheeses may need to be avoided, as they could suffer from potentially serious symptoms caused by a reaction to the fungi.

The most common symptoms associated with fungi spore inhalation or ingestion include:

  • Nausea
  • Skin irritation
  • Breathlessness
  • Coughing
  • Gastrointestinal discomfort
  • Vomiting

It is important to note that if you are pregnant, blue cheeses are also suggested to be avoided.

Is it safe to cut mold off the cheese and eat the rest?

Removing mold from the surface of blue cheese in order to consume what’s left is not advised, as when it forms, it grows roots (called threads), which burrow down into the deeper parts of the cheese.

These threads can spread mycotoxins through the rest of the cheese, causing a breakdown in its taste and texture, as well as being a toxic substance that can cause many symptoms, even occasionally in healthy individuals.

The only intentional mold that should be forming within blue cheese is the penicillium strain that is used to create the blue “veining” throughout the cheese. This particular strain does not produce the aforementioned mycotoxins, and should not cause any harm if eaten, however, any found forming on the exterior of the cheese indicates that the cheese was not stored properly, and could be potentially harmful.

The other factor to consider is that it most often grows under the same circumstances as bacteria, and so the growth of fungi could also indicate the presence of these harmful bacteria such as E. coli, which can cause food poisoning if consumed.

What does the mold that grows on an aged blue taste like?

As blue cheese types have distinctive tastes and textures, it can be difficult to pinpoint the exact taste that penicillium roqueforti imparts. However, it is often described most accurately as being slightly sour, almost spicy, or tangy in taste and responsible for creating a crumbly or creamy texture.

What is the orange mold on the cheese?

Commonly spotted as furry patches of orange on an aged blue, Sporendonema casei is a harmless strain of fungi that can enhance both its flavor and texture profiles. This strain can form on any blue cheese and is not known to cause any ill health in humans or animals, in fact, it is often considered to be a sign of a well-aged and high-quality cheese.

Why are types of cheese like Stilton ok to eat?

Blue mold on and in cheeses such as Stilton, Brie, and Gorgonzola are safe to eat, as it comes from the Penicillium Roqueforti strain that is introduced, which does not produce mycotoxins.

Mycotoxins are released by fungi as a defensive mechanism against microbes, and so their ingestion or inhalation can cause a lot of health complaints, especially in those with suppressed immune systems or allergies.

Without mycotoxins, Penicillium roqueforti is not only perfectly safe to eat, but can, in fact, have numerous health benefits, including slowing aging, anti-inflammatory properties, and lowering both cholesterol and blood pressure.

Should it have a fuzz on it?

No, blue cheeses should not be fuzzy on their surface or rind. Finding this growing on the cheese indicates that it has begun to spoil and is growing unintended and could potentially be harmful.

By this point, the cheese will have almost certainly begun to turn rancid. You can tell if this is the case by using your nose, as rancid cheese will produce an ammonia-like smell. We’re you to taste the cheese at this point, you would notice it had a strong, sour, and very unpleasant taste and would have a gritty texture.

What about black mold on an aged blue?

Black mold on any cheese, (in this case blue cheese in particular), nearly always indicates that the cheese is bad and should be discarded.

The strain that grows in black patches on cheese is called Aspergillus Niger, and though it is not as harmful as Stachybotrys chartarum, it can still pose a number of potential health threats, so the cheese should be discarded immediately if it is discovered.

The exception to the rule is if the black spots are within the blue veining of the cheese. If this is the case, then it is most likely part of the harmless penicillium fungi, as this can sometimes present as small black dots mixed in with the blue-colored growth.

How quickly do they go moldy?

If left under the correct circumstances, blue-veined cheese can begin to grow moldy exceptionally quickly. For example, if you were to leave a block of open blue cheese out on a kitchen counter, within only a few hours, fungi spores could settle and begin to develop into a colony.

Should the cheese be left at room temperature for longer, in only a matter of a day or two, large patches of fungi will cover its surface and a fuzzy texture will be present.

How to prevent bad mold

Poor storage methods are the number one cause of blue cheese going bad, so making sure it is stored properly in the first place is the best way to prevent fungi growth and extend the cheese’s shelf life.

Use the following tips to stop your blue cheese from growing mold:

Store in the bottom of the fridge, towards the back

The lowest parts of a refrigerator not only keep the most consistent temperatures but also have the lowest humidity levels. This helps to create a hostile environment for both fungi and bacteria, prolonging their shelf-life.

If possible, try to store the cheese towards the back of the fridge as well as on the bottom, as this helps to shield it against temperature fluctuations whenever the door is opened or closed.

Use a salad crisper

If you own one, a salad crisper drawer is perfect for storing your blue cheese, because as it is in a separate drawer, the cheese will be completely guarded against sudden temperature fluctuations.

In some crispers you can also set the humidity levels, giving you complete control over the environment your cheese is kept in.

Wrap it in parchment paper

Cheeses need to breathe, and wrapping them in plastic impacts their ability to do so, which will harm the microbes within that provide its characteristic taste and textures, resulting in a bland-tasting cheese. It can also impart a “plasticky” taste to the cheese, spoiling it.

However, leaving the cheese unwrapped is also unwise, as the cheese can suffer from cross-contamination with other flavors from the fridge as well as drying out.

To prevent this, wrap the cheese in parchment (wax) paper. This will allow the cheese to breathe whilst preventing it from becoming dry. It also stops moisture buildup on the surface of the cheese.

Keep it in an airtight plastic or glass container

Whilst cheese does need to breathe, keeping it in an airtight container will still allow enough air for it to do so, whilst preventing any cross-contamination from other food items.

It also stops fungi and bacteria from finding their way onto the cheese from other food items or airborne spores within the refrigerator.

Store it at 40 degrees Fahrenheit or below

Blue cheese should be stored at 40 degrees Fahrenheit or below in order to keep it fresh for as long as possible.

Cooling cheese does not always prevent fungi growth entirely, but it greatly slows down the rate at which it can spread. Bacteria can also breed at rapid rates once the temperature rises above 40 Fahrenheit, so keeping it below this level will help to maintain its freshness.

Freeze it

Should you find yourself with more blue cheese than you can consume before its best-before date, you have the option of freezing it.

In order to freeze the cheese correctly, wrap it in parchment paper, then place it in a zip lock freezer bag. Press out as much of the air as possible within the bag and then place it in the freezer.

Frozen blue cheese can stay fresh for months or even years, however after 6 months its taste may become more bland and its texture can become slightly gritty.


Blue cheese is as susceptible to mold growth as other semi-soft cheeses, so proper storage is incredibly important to ensure it does not spoil faster than needs to be. This can be achieved by keeping it in a refrigerator at 40 degrees Fahrenheit, wrapped in parchment paper, and in an airtight container.

Penicillium roqueforti is deliberately added to impart its characteristic taste, texture, and blue “veining”, is harmless to consume for most people, although people with allergies, suppressed immune systems and those who are pregnant should still avoid consuming it.

Chris Walker

Chris Walker has struggled for several years with mold after buying his own property. After finding the solutions to several issues around his home, he decided to create this site in order to answer as many questions about mold and mildew as possible to help others dealing with the same problems.

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