Gruyere cheese is a hard Swiss cheese with a salty, creamy, and nutty flavor. It is commonly used as a table cheese as well as being an excellent melter, so is also used in gratins, quiches, and fondues.
So, what are you to do when you go to your fridge to pick out your Gruyere cheese to use in your next meal, only to find it has mold growing on it?
Can you still eat the moldy cheese? Can you cut off the moldy parts and eat the rest? Is the mold dangerous, and how can you prevent this from happening again?
In this article, we will be answering all these questions and more, so, for all you need to know about mold growth on Gruyere cheese, keep reading.
What causes mold on Gruyère cheese?
Despite Gruyere being a hard cheese, it is still susceptible to mold growth. It can form as long as the conditions are correct to support it, which include: having a source of moisture, access to nutrients and oxygen as well as being within the correct temperature range to facilitate rapid growth.
Poor storage conditions are the most common cause of the cheese becoming moldy, and these can be easily rectified to preserve the life of the cheese and prevent future growth.
Let’s take a look at each element to see how you may be inadvertently providing mold with just the environment it needs.
Most US refrigerators have an ambient humidity of between 30-50%, and as mold only needs the humidity to reach 55%, all it would take is a few uncovered saucepans with leftover food in them, or warm foods to be placed in the fridge before they have cooled properly to raise that level past 55%. Once this level has been reached, mold will be able to grow happily on many items within a refrigerator, including your expensive cheese.
Hard cheeses also “sweat”, and so wrapping them directly on plastic wrap can not only impart a “plasticy”, taste on the cheese but can also trap a layer of moisture around its surface, this is perfect for mold to use for hydration.
All the nutrients mold needs are within the cheese itself. The carbohydrates, proteins, fats, and minerals can all be used as food for mold, it simply settles on the cheese, releases enzymes that break the cheese down, and absorbs the nutrients within it.
As we will later see, the type of mold that is most likely developing on your Gruyere cheese can grow relatively well even at refrigerated temperatures, however, even slight increases can rapidly increase the rate at which it can do so.
Poor storage practices, such as storing the cheese on the top shelf of the fridge, broken gaskets (seals), and faulty thermostats are major causes of temperature fluctuations in fridges that can increase the likelihood of mold growth.
What type of mold grows on Gruyère?
The Penicillium strain of mold grows on hard cheeses such as Gruyere. It begins life as white patches of woolly or velvet-like patches of circular growth.
Over time, the growth can change from white to blue, blue-green to olive green in coloration. This strain is often found growing on decaying vegetation, within soil, and on dried foodstuffs such as cereals and grains.
Is the mold on Gruyère cheese dangerous?
Yes, penicillium mold has the ability to produce mycotoxins as a defense mechanism whenever it is disturbed or feels threatened.
These mycotoxins can cause unpleasant symptoms in healthy individuals, such as nausea, gastrointestinal discomfort if ingested, skin irritation and breathlessness, and coughing if inhaled.
For individuals with suppressed immune systems or allergic asthma, serious symptoms such as organ damage and some cancers have been reported.
What is the white stuff on Gruyère cheese?
The good news is, the most likely cause of white patches on your Gruyere cheese is not mold growth, although at first glance you may think this to be the case.
Calcium lactate crystals form on the surface of cheese as it ages and appear as a white powdery substance with a grainy texture. This is not only nothing to worry about, as it is entirely edible, but is in fact a sign of a well-aged, mature cheese.
To tell if what you are seeing is mold rather than calcium lactate crystals, look at its texture. Calcium lactate crystals will have a grainy “sand-like” texture, whereas mold will be soft and cotton-like.
Can you cut mold off Gruyère?
No, despite what you may have heard or read about being able to cut the moldy parts of a hard cheese off and eat the rest, this is certainly not advised, as during the removal process, you may disturb the mold, causing it to release spores that will settle on other parts of the cheese.
Another consideration is that mold often grows on cheese when it is beginning to turn rancid, meaning the cheese that is left without mold would be unpleasant to eat anyway.
The final (and potentially most important) consideration, is that mold and bacteria often grow under very similar circumstances. So whilst you may remove mold from the cheese, leaving it looking like the rest is perfectly fine to eat, it could be harboring dangerous bacteria, such as E. coli.
How to prevent mold on Gruyere cheese
Much more effective than trying to deal with mold that has formed a colony on your Gruyere or any cheese for that matter, is to prevent it from occurring in the first place.
With that, the following steps will help you prevent mold growth on Gruyere cheese and increase its shelf-life considerably.
The lowest points of a refrigerator have not only the lowest and most consistent temperatures but also the lowest humidity, so placing your Gruyere cheese here in its packaging protects it from the higher temperatures that can be found nearer the top of the fridge.
Placing the cheese towards the back also helps shield it from temperature fluctuations whenever the fridge door is opened and closed.
Wrap it in parchment paper and plastic wrap
Cheese needs to breathe, but you still want to control the level of moisture and prevent any cross-contamination of your Gruyere whilst it is on the refrigerator. So, wrap the cheese in parchment paper, doing so will absorb any excess moisture, creating a less hospitable environment for mold and bacteria.
You can further protect the cheese by wrapping it in an additional layer of plastic wrap. This will retain enough moisture to stop the cheese from drying, but keep out any spores or bacteria.
Use a salad crisper
If your fridge has a salad crisper drawer, this is an ideal place to put your Gruyere cheese. Salad crispers have lower humidity levels, and more consistent temperatures, and the drawer itself will help protect against temperature fluctuations.
Check your thermostat
In order to stay fresh for the longest possible time, and to slow the rate of mold and bacteria growth, Gruyere cheese should be stored at 40 degrees Fahrenheit or slightly lower.
Check your fridge’s thermostat to make sure it is set within this temperature range, and to test if it is working correctly, place a thermometer on one of the shelves and check it each time you open the door.
If you have purchased more Gruyere than you will be able to use before its best-before date, you have the option to freeze it until you need it next.
Frozen in a block, Gruyere cheese will last for at least six months in a freezer before it begins to lose some of its taste, and its texture may start to deteriorate slightly. However, freezing the cheese will keep it protected against me and bacteria growth indefinitely. The cheese will retain its excellent melting characteristics even after being frozen.
Gruyere cheese can become moldy despite its low water content. The most common strain of mold to form on the cheese is Penicillium, which can cause serious health complaints in some people.
The most effective way to prevent mold from growing on the cheese is to wrap it in parchment paper, followed by a layer of plastic wrap, then store it in the bottom of the refrigerator, as close to the back as possible.