There are thousands of varieties of cheese available across the world, each with its own delicate tastes and texture profiles. They are delicious on their own or as an ingredient in countless dishes.
However, they are susceptible to mold and bacteria that can render them inedible and even potentially harmful to consume. So, can you still eat cheese if you cut off the moldy parts? What type of molds grow on cheese and how can you keep yours fresh for as long as possible?
In this article, we will be answering all these questions and more, so, for all you need to know about mold growth on cheese, keep reading.
What is mold?
Mold can be found throughout the world in thousands of varieties. They can grow anywhere there is sufficient hydration, nutrition, and oxygen, and play an important role in nature, as they assist in breaking down organic matter such as dead leaves and debris.
It spreads by producing spores via multicellular structures called hyphae, which are then released into the air. When these spores land on a surface with acceptable conditions, they will begin to breed and create a new colony.
Mold does need relatively high moisture levels in order to thrive, (usually greater than 55%), so it is frequently seen growing in high moisture rooms of the house such as the kitchen, bathroom, basements, attics, or anywhere that has suffered from water damage.
Why does cheese grow mold?
Cheese gets moldy because if improperly stored, it can provide everything that mildew and other fungi need. Let’s take a deeper look into some of those elements and how cheese may be providing them.
Most people store their cheese in a refrigerator in order to keep it fresh for as long as possible. However, the ambient humidity of most fridges lies between 30-50%. Mold only needs 55% humidity, so it only takes a few meals that have not yet fully cooled being placed in the fridge, or open pans of sauce to raise the humidity level to an acceptable degree for mold.
Wrapping the cheese in plastic is another common mistake, as cheese “ breathes”, and releases some of its moisture. If it is wrapped tightly in plastic, the moisture cannot escape, and so it pools, providing all the moisture mold and bacteria could ever need.
Nutrients are provided by the cheese itself, as it contains all the fats, proteins, carbohydrates, and minerals that fungi need to live. As it grows on the surface of the cheese, mold releases enzymes that digest and break down the elements within it, these are then absorbed.
Mold is an obligate aerobe (an organism that requires oxygen to breathe. Of course, oxygen is everywhere, and fungi only need a very small amount, but limiting this with the intention of preserving cheese, is not always a good idea. Microbes living within the cheese will also be killed if you completely restrict oxygen from it, which will dull its flavor and spoil its texture.
You are also more likely to trap moisture around the surface by doing so, encouraging any mold that has settled on it to grow.
Why does cheese mold before its expiration date?
If cheese is stored correctly, it should not become moldy before the expiration date. Food manufacturers conduct tests to see how long their product should last before going bad if stored correctly and determine this to be their “use-by” date.
Should you find that your cheese has become moldy before this date, you have likely stored the cheese at too high of a temperature, allowed moisture to form around the cheese, or left it at room temperature for too long.
Either way, the food will have been stored incorrectly for this to have occurred.
What kind is it?
The most common strains of molds found growing on various cheeses are:
- Penicillium Roqueforti
- Penicillium glaucum
- Penicillium candidum
Many of these molds are intentionally added to the cheese, or are used within the process of making them, and are generally harmless to humans and animals. However, if improperly stored, additional strains of mold that grow on food may also find their way onto your cheese. These molds can make cheese inedible, with some of the most common strains found on food being:
Without proper testing, it can be difficult to determine which types of mold are intentional and safe to eat, and which could be harmful.
As a general rule, mold that forms on the surface of the cheese after you have purchased may not be intentional and so caution should be used when handling it. Cheeses such as Brie or Camembert will already have mold on them when you purchase them, so you can be sure this is safe to eat as long as you have no allergies to them.
Is it dangerous?
Molds that are purposely added to blue cheeses such as Brie, Camembert, and Roquefort will pose no threat to healthy individuals. However, those with suppressed immune systems, allergies, or those who are pregnant should avoid these cheeses, as they could still cause health complaints and complications.
Penicillium mold is the most common strain of mold found on cheese, and this strain can potentially cause health complaints, as it can produce a toxic substance called mycotoxin as a defense mechanism against microbes.
Healthy individuals can consume or inhale small amounts of spores released from penicillium mold without issue, but larger quantities can cause symptoms similar to food poisoning, breathing difficulties, and other immune responses.
Additional strains of mold can form on cheeses such as Altenaria, Aspergillus, Botrytis, and Cladosporium that commonly form on food items within the home all have the potential to develop mycotoxins, and so unintentional growth of mold on any type of cheese should always be treated with caution.
Some of the common symptoms of allergies to mold include:
- Gastrointestinal discomfort
What about green moldy cheese?
Green mold is common on cheese, and it is most likely a result of the penicillium strain, as this can start life as a white powdery substance that can change its color to blue or green.
There are also slightly different strains of penicillium that may be more prone to growing with a green color, so the suggestion to treat this mold with caution still remains.
How long does it take for mold to grow on cheese?
Under the right circumstances, mold can grow on cheese exceptionally quickly. For example, if a piece of cheese is left out of the refrigerator and allowed to come to room temperature, within only 2 hours mold spores (as well as bacteria) will have had time to settle on the cheese and begin to breed.
The mold will be microscopic at this point, and so will not be visible to the naked eye, but if left under the same circumstances, within a day, large, circular patches of mold growth would become visible. At this point, it’s also possible that a strong musty scent would start to emanate from the mold.
Which cheeses are made with fungi?
There are several varieties of cheese that without the use of mold, would not exist. Mold is added to the curd of some cheeses in order to alter their taste and texture profiles, and other varieties have mold added to the exterior of the cheese to develop their characteristic rinds.
Examples of cheeses made with mold added to curds include:
And examples of cheese with mold added to their exteriors (called bloomy rinds) include:
- Buche de Chèvre
What does moldy cheese look like?
How mold appears on cheese depends entirely on which strain of mold is growing, and how long it has been growing for.
However, many fungi (especially those that grow on cheese), will start life as small, white patches of circular growth with a fuzzy texture. Over time, the color may change to green, blue, blue-green, olive, or even yellow or pink.
Other strains can appear in similar coloration but may have a different texture, for example, aspergillus will form in blue-green patches with a suede-like surface.
Intentional molds (such as those added to the exteriors of cheese to create their rind, will often be white and will have a “fluffy” texture.
What does mold on shredded cheese look like?
Shredded cheese makes mold far more difficult to spot, especially in the early stages. This is because wood pulp that is white in color is used to keep the shreds separated, and so disguises any early formation.
What you may see, is clumping together of the shreds, and some small patches of white, blue, or green growth. Still, this can be difficult to see within a full bag of cheese, so it may be more efficient to use your sense of smell.
Once you open a bag of shredded cheese that has begun to turn moldy, you will be able to smell one of two distinctive smells. You will either smell a strong musty odor, which indicates the growth of mold, or, you will smell a strong sour taste, which indicates the cheese has begun to turn rancid.
Once cheese has turned rancid, not only is it very unpleasant to eat, but the likelihood of mold growth becomes far higher.
What is the white stuff on cheeses?
The good news is that in many cases, the white formation you see growing on many cheeses and especially aged cheeses is in fact not mold. It is more often the formation of calcium lactate crystals.
These crystals are the calcium salt of lactate acid, naturally occurring within all cheeses. Bacteria and microbes break down the lactose (milk sugars) within the cheese and create lactate acid, as this acid binds with calcium ions, small crystals appear on its surface.
These crystals are not only perfectly edible but are a sign of a well-aged, mature cheese with an intense flavor profile.
One way to test if the white substance on your cheese is mold or calcium crystals is to look at its texture. Calcium crystals will be gritty to the touch, whereas mold will often be fluffy or powdery. Remember, if you have any allergies, do not attempt to touch what you think may be mold, or you could inhale its spores.
Is moldy cheese safe to eat?
Cheeses that have mold deliberately added to them will be safe to eat for most healthy individuals, with the exception of people with suppressed immune systems, allergies, and those who are pregnant.
The unintentional mold that has grown on cheese should not be consumed, as there is a possibility that whichever strain has grown could be capable of producing mycotoxins that can cause food poisoning-like symptoms, as well as breathlessness and other allergic reactions, even in otherwise healthy people.
Can you cut off the spoiled parts and eat the rest?
You will often read that it is perfectly fine to cut 1 inch away from the moldy parts of hard cheeses and eat the rest. And whilst this may be fine for many people, there is still the possibility of allergic reactions to mold spores that were present on the cheese.
The reason for this is that many molds can release their spores very easily, and even the act of cutting and removing the moldy parts may have caused a release of its spores, which may have then settled on the rest of the cheese, resulting in you still consuming the spores.
If you have no allergies and a fully functioning immune system, this is probably fine advice, but if you have any allergies, it is advisable to discard the cheese entirely, rather than run the risk.
For soft cheeses, any sign of mold growth requires the cheese to be discarded. This is because mold grows roots (called threads), that burrow down into the deeper parts of the cheese and can spread mycotoxins throughout. Even if you were to scoop away a large chunk of cream cheese with mold on it, the remainder of the tub could still be filled with toxins.
The other factor to consider here, is that mold and bacteria grow rapidly under similar circumstances. So, that is to say that should you find mold growing on a piece of cheddar for example, there is a good chance that a high level of bacteria is also present. Some of these bacteria such as E. coli can be very harmful, and so removing the mold from the cheese and eating what appears to be otherwise perfectly good cheese could result in a case of food poisoning.
What if you accidentally ate moldy cheese, or will you get food poisoning?
If you accidentally ate cheese with mold on it, in the majority of cases you would not need to do anything about it. It’s highly likely that the amount you consumed will cause little to no symptoms unless you were very unlucky.
Of course, it goes without saying that should you start to suffer from symptoms directly after consuming moldy cheese, you certainly should seek medical advice.
How to prevent cheese from going moldy
As previously discussed, the number one cause of cheese going moldy in the first place is poor storage, so making sure you are keeping your cheese in the correct conditions will be the best way to prevent fungi and bacteria growth from spoiling it.
The bottom of a fridge not only has the most consistent temperatures but also the lowest humidity levels, making it an excellent place to store cheese.
If possible, keep it towards the back of the refrigerator, as this area is somewhat protected from temperature fluctuations when the door is opened and closed.
Wrap it in parchment paper
As stated, cheese needs to breathe, and so wrapping it tightly in plastic not only imparts a “plasticky” taste but can starve the microbes within the cheese of the oxygen they require, which can have a negative effect on its taste and flavor profile.
Instead, wrap the cheese in parchment (wax) paper, as this will allow circulation whilst protecting the cheese from cross-contamination with other food items and stops moisture from building up on its surface, preventing mold.
Use a salad crisper
If you have one, store your cheese in a salad crisper drawer. This area of the fridge not only prevents temperature fluctuations but maintains a constant and regulated humidity level. The drawer itself protects well against cross-contamination and some even have the ability to control the humidity levels, allowing you to be in complete control of the environment your store your cheese in.
Many kinds of cheese have different recommended humidity levels, so you should check these before setting the humidity level in your crisper.
Store it at 40 degrees Fahrenheit or below
Cheese should be stored at 40 degrees Fahrenheit in order to keep it as fresh as possible for the longest time. Keeping it below this temperature will also help to slow the rate at which mold and bacteria can spread.
Some strains of fungi can still grow at 40 degrees Fahrenheit and lower, but the rate at which they will grow will be much slower.
Check your thermostat
Further to the previous point, it’s important to check that not only your thermostat is set to the correct temperature, but that it is functioning correctly.
In order to make sure your cheese is being stored at a consistent temperature, place a thermometer on the lowest shelf where it is being stored. Check it several times throughout the day to make sure it is staying at the right temperature.
Keep it in an airtight container
Keep your cheese in an airtight container to prevent cross-contamination and to prevent mold and bacteria growth.
Cheese does need airflow, but a plastic or glass container with a lid will provide plenty of oxygen without allowing mold spores to find their way onto the cheese and maintain a consistent moisture level, preventing the cheese from drying out.
Check its use-by date
Cheese is given a use-by date so you can determine approximately how long it should last before it should begin to turn rancid.
Whilst you are purchasing your cheese, check the use-by date to make sure you are only buying what you will be able to consume before this date.
If for whatever reason you have purchased more cheese than you can consume before its use-by date, you have the option of freezing it.
Hard and semi-hard cheeses can be wrapped in parchment paper and placed into a ziplock bag with all the air pushed out and then frozen.
Once frozen, many kinds of cheese will last at least 6 months before their flavor begins to become more bland and their textures compromised.
Soft cheeses such as cream and cottage cheese can also be frozen, but their high water content will not react well to being frozen and their texture may become spoiled.
Cheese of any type can be affected by mold growth if not stored correctly. Penicillium is the most likely strain to grow and many others are deliberately added to specific cheeses to alter their flavor and texture profiles. To prevent mold and bacteria growth on cheese, store it in the bottom of a fridge, towards the back whilst being wrapped in parchment paper and in an airtight plastic or glass container at 40 degrees Fahrenheit.