Mozzarella cheese is a widely available, popular cheese used on pizzas, salads, and in several other pasta dishes.
So, what happens when you go to your fridge to pick out your mozzarella cheese to use in your favorite dish, only to find the cheese has mold growing on it? Why has this happened in the first place, can you cut off the moldy cheese and eat the rest and how can you stop this from happening again?
In this article, we answer all these questions and more, so, for all you need to know about mold on mozzarella, keep reading.
Why does mozzarella grow moldy?
Fungi will grow very easily on cheese as long as the conditions are right for it, and much as fungi can be complex organisms, their needs are fairly basic.
All fungi need to grow, is a source of moisture for hydration, nutrients for sustenance, and the correct temperature range for it to grow.
Mozzarella cheese is a semi-soft cheese, which means its water content is higher than hard cheeses such as cheddar but lower than cream and cottage-style cheese. The amount of moisture within mozzarella is still adequate for fungi to live off happily, so its hydration requirements are easily met. Mozzarella can develop fungal growth faster than other types of cheese, and this is likely due to its moisture content.
Mozzarella cheese also provides the fats, minerals, proteins, and carbohydrates that fungi can use as a source of nourishment, so these needs are also met.
The temperature that the cheese is kept at plays a big part in how quickly it will begin to mold, as keeping it refrigerated will certainly slow the rate at which the cheese becomes rancid and grows fungi, but even slight fluctuations in temperature, or being left outside of the fridge for too long can rapidly increase the rate at which both molds and bacteria can begin to spread across both the surface and interior of the cheese.
Mozzarella cheese is also a type of cheese that is meant to be eaten whilst it is fresh because it is a soft cheese and has no preservatives (such as salt) that many other cheeses contain. Mozzarella is packaged in brine, water, or whey which helps to keep the cheese fresh for longer, but if removed from the liquid, it had very little defense against fungal growth and bacteria.
Does mozzarella cheese mold easily?
As molds requirements are easily met by mozzarella cheese, it can, indeed grow easily, and whilst there is nothing you can do about the level of moisture or nutrients within the cheese (without spoiling its delicate taste), the way the cheese is stored is the biggest factor you can influence to slow the growth of fungi and increase its shelf-life.
The brine or any other liquid that the mozzarella cheese comes in acts as a defensive barrier, so keeping it in this fluid will help to preserve it, whilst draining it will certainly cause it to grow mould much more quickly.
What strains grow on mozzarella?
There are two main varieties of fungi that are commonly found growing on mozzarella cheese, one of which is penicillium, and the other is pink mold or Serratia marcescens.
These strains are found growing within soil, rotting vegetation, fresh fruit, and vegetables, and on some cereals, as well as being the most commonly seen growing on and within the cheese. Its spores are airborne, so they can find their way into the milk that’s used to make mozzarella cheese, or at any point in the production and storage stages.
Serratia marcescens (pink mold), is in fact, not a fungi at all, but is instead a strain of bacteria commonly found growing in bathrooms and other high moisture areas, it can also very easily live on food items.
What does moldy mozzarella cheese look like?
The most obvious signs of fungal growth on mozzarella cheese are white, blue, and blue-green to olive green-colored circular patches of growth with a texture that can appear powdery, velvet, or cotton-like.
By this point, the cheese itself will likely already have begun to turn rancid, as this is often when fungi will begin to develop, some signs to look out for rancidity include: discoloration, dryness, hardening of the edges, and formation of surface cracks. The smell of the cheese will also become slightly sour, so even if you cannot see any surface mildew if any of these other symptoms are present, you may need to discard the cheese.
What color is fungal growth on mozzarella cheese?
Whilst penicillium strains are most commonly found growing on mozzarella cheese, others can grow and are found growing on many other types of cheese. The color the fungus grows can be a good indication of which particular strain you are dealing with, so the following breakdown may help to assist you in determining the next steps you should take.
Many strains of fungi can form with black coloration (such as Aspergillus), with some more toxic than others. It is very difficult to know without testing which strain you would be dealing with, but as some strains of black fungi can be highly toxic, it is best to avoid any contact with it and discard it safely as soon as it is seen. Black mold grows fairly rarely on cheese, but under the correct circumstances, it certainly can happen.
Green mold found growing on mozzarella can either be from penicillium strains as these sometimes present with an olive green coloration, or aspergillus, which more often has darker tones, but can also be green. Both these strains have the ability to produce mycotoxins, so should be handled with care and contact avoided if possible.
Penicillium expansum is the strain that would cause blue velvet or powdery textured growth on mozzarella cheese, it is the same strain that gives blue cheese its color, and it again can produce mycotoxins which can cause health complaints in some individuals. Harmless varieties of penicilium are commonly added to blue cheese and other types in order to produce their characteristic blue veining and flavor profiles.
Should you find pink fungal growths growing on your mozzarella or any other kind of cheese, rest assured that it is more likely to be the bacteria Serratia marcescens. This bacteria grows on food items and has a pink hue, it is not often as hazardous to human health as molds, however, it can cause intestinal problems and in rare cases, pneumonia, so it is best avoided if you spot it growing on any type of cheese.
What if you accidentally ate moldy mozzarella, or were to eat expired cheese, could you get food poisoning?
Yes, molds have the ability to produce mycotoxins as a defense mechanism whenever they are disturbed or feel threatened. It is also highly likely the cheese may have become rancid, and so could have a large amount of bacteria present that could lead to food poisoning symptoms.
In most individuals, eating mold from cheese or from any other type of moldy food, and being exposed to a small amount of mold spores will cause little harm, but in those with suppressed immune systems, or those with allergies, it can cause the following symptoms:
- Gastrointestinal discomfort
- Skin irritation
Even in otherwise healthy individuals, these symptoms can present if the amount of mold ingested or inhaled was significant enough.
The other factor to consider is that often fungi and bacteria grow under the same circumstances, so there is a very real danger that a large buildup of bacteria could also have formed on the mozzarella at the same time as mold.
E. coli bacteria can cause food poisoning, and even small amounts can cause unpleasant symptoms, so if you notice any signs of mold on mozzarella or any other moldy cheese, they should be discarded. Food poisoning has the potential to become a medical emergency for some people if not treated, so this is something to be taken seriously.
However, if you accidentally ate a small amount of shredded cheese (mozzarella or not), that had mold on it, you would not need to seek medical advice unless you began to suffer from symptoms.
Is it ok to cut the moldy parts off the mozzarella cheese?
You may have heard that should you find a small patch of mold growing on mozzarella or many other types of hard-to-semi-hard cheese, it is fine to cut this part off and consume the rest.
This is not recommended, as spores can move onto other parts of the cheese whilst it is being cut and can still end up being ingested.
Fungi also have threads (similar to roots), that can burrow deeper into the cheese, so cutting away the moldy part may not remove all traces and may still be consumed. The mold may also have released mycotoxins into the cheese without any obvious visible sign, and again, removing the top layer would not remove these from the deeper parts of the cheese.
If you see mold growing on mozzarella cheese, it is not worth the risk to try to save it by cutting away the growth. It could still be dangerous to eat and would not taste or smell particularly nice. This is the case if you were to eat expired cheese of any type.
How to keep mozzarella cheese from molding
Prevention is always the best cure, and we have already discussed that once mozzarella has become moldy, no part of it should not be eaten. So, the following are some tips you can use to prevent mozzarella from going bad and to slow the rate of both fungus and bacteria growth.
Keep it in its liquid
Keeping mozzarella cheese in the liquid it came in is one of the best ways to preserve the cheese and prevent mold growth directly on the cheese itself.
If you have thrown away the liquid, you can replace it by reading the packet it came in. If it came in water, simply cover it with water again and place it in an airtight container in your fridge.
If it came in brine, add one teaspoon of salt for each cup of water and again place it in an airtight container in your fridge. Make sure all of the cheese is submerged in the liquid.
Check your refrigerator thermostat
Keeping the mozzarella at a consistent temperature of 40 degrees or lower will help extend the shelf life of the cheese and prevent fungal growth. Check the thermostat on your fridge to ensure it is working correctly and set to the right temperature.
If you are uncertain about the exact temperature within your fridge, consider purchasing a thermostat and placing this on one of the shelves.
Don’t leave it out
Leaving mozzarella out of the fridge for any longer than necessary is a surefire way for it to spoil faster and for mold and bacteria to start to spread.
Place unused mozzarella back in the fridge as quickly as possible, and consume any cheese shortly after being removed to ensure it does not dry out and grow bacteria and mold.
Any cheese that is accidentally left on the counter should be thrown away if left longer than two hours, as by this point it will have begun to spoil.
Store in an airtight container
Keep unused mozzarella cheese in an airtight container in the fridge. Mold needs oxygen, so denying it this important resource makes it a more inhospitable environment for mold to grow in.
The container will also protect the cheese from cross-contamination of other food items within the fridge, and help to maintain a more consistent temperature by protecting it from fluctuations when the door is opened and closed.
The bottom of the fridge has the most consistent temperatures, as warmer air will rise to the top shelves. If warm items are stored in the fridge, the cheese will also be protected from the warm air rising from these items.
Storing toward the back of the fridge is also beneficial, as this area is furthest from the door and will be less impacted by fluctuations in temperature when the door is opened.
If you find yourself with an abundance of mozzarella cheese that you will not be able to use before its expiration date, you can increase its shelf life and decrease mold and bacteria growth by freezing it.
The act of freezing cheese may impact the flavor and texture, but it can still be used within pasta dishes and will maintain its melting ability.
Check its use-by date
Soft types of cheese such as mozzarella have shorter expiration dates than hard cheeses due to their high water content. It is best therefore to check the expiration date on the cheese you plan to buy to make sure you will be able to consume it before this date.
You may be able to eat the cheese an extra day or two past its expiration date, but the likelihood of the cheese becoming rancid and bacteria or mold growth occurring greatly increases after this date has passed.
What does moldy mozzarella taste like?
The most commonly reported taste of moldy cheese is that of sourness that comes with an unpleasant odor. It may also have an uncharacteristic soft texture, instead of the stringy, moist mouth feel you would expect.
Can you still use mozzarella with mold?
It is not advisable to use mozzarella cheese that has mold growing on it, without testing, it would be very difficult to determine which strain you were dealing with, so there is a chance that it could be toxic. Even if you have no allergies, ingesting mold can cause illness, and generally, mold grows on cheese that has begun to turn rancid, which would have already spoiled its taste and texture.
What does moldy mozzarella smell like?
The smell of moldy mozzarella is likely to be a combination of both a mustiness and sourness. As mold tends to grow on cheese that has begun to become rancid, the sour smell of milk that has turned would be present.
Be careful when smelling the mozzarella, as if there is indeed mold growth, you could accidentally inhale its spores, which can cause unpleasant
symptoms in some people.
Mozzarella is a soft cheese that has a relatively short shelf life due to its high water content. Penicillium is the most commonly found strain of mold to grow on it, and this can cause health complaints if consumed. Ensuring proper storage techniques are utilized is the best way to prevent mold growth on the cheese and if any signs of mold growth are noticed, it should be discarded.