Mold On Mozzarella Cheese: Is It Still Safe To Eat?

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 to use in your favorite dish, only to find it has mold growing on it? Why has this happened in the first place, can you cut off the moldy parts 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.

Mold on mozzarella cheese

Why does mozzarella grow mold?

Mold will grow very easily as long as the conditions are right for it, and much as fungi can be complex organisms, their needs are fairly basic.

All mold needs 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 cheeses. The amount of moisture within mozzarella is still adequate for mold to live off happily, so its hydration requirements are easily met.

The cheese also provides the fats, minerals, proteins, and carbohydrates that mold 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 mold, 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.

Mozzarella cheese is also a type of cheese that is meant to be eaten whilst it is fresh, because of this, it lacks the 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 mold and bacteria growth.

Does mozzarella 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 mold and increase its shelf-life.

The brine or any other liquid that the mozzarella 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 mold much more quickly.

What types of mold grow on mozzarella?

There are two main varieties of mold that are commonly found growing on mozzarella cheese, one of which is penicillium, and the other is pink mold or Serratia marcescens.

Penicillium molds are one of the most common strains and are found growing within soil, rotting vegetation, fresh fruit and vegetables, and on some cereals. Its spores are airborne, so they can find their way into the milk that’s used to make mozzarella, or at any point in the production and storage stages.

Serratia marcescens (pink mold), is in fact, not a mold 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 mold look like on mozzarella cheese?

The most obvious signs of mold 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.

The cheese itself will likely already have begun to turn rancid, as this is often when mold 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 mold if any of these other symptoms are present, you may need to discard the cheese.

What color is mold on mozzarella?

Whilst penicillium strains are most commonly found growing on mozzarella cheese, others can grow. The color the mold 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 mold 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 mold can be highly toxic, it is best to avoid any contact with it and discard it safely as soon as it is seen.


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.


Should you find pink mold growing on your mozzarella, 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.

Can eating moldy mozzarella make you sick?

Yes, molds have the ability to produce mycotoxins as a defense mechanism whenever they are disturbed or feel threatened.

In most individuals, a small amount of exposure to mold or its spores will cause little harm, but in those with suppressed immune systems, or those with allergies, it can cause the following symptoms:

  • Headache
  • Nausea
  • Vomiting
  • Gastrointestinal discomfort
  • Diarrhea
  • Breathlessness
  • 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 mold 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, it should be discarded.

Is it ok to cut old off mozzarella cheese?

You may have heard that should you find a small patch of mold growing on mozzarella, it is fine to cut this part off and consume the rest.

This is not recommended, as spores from the mold can move onto other parts of the cheese whilst it is being cut and can still end up being ingested.

Mold also has 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.

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 preserve your mozzarella for longer and to slow the rate of both mold 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 mold. 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.

Store in the back of the fridge on the bottom shelf

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.

Freeze it

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 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 cheeses 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 mozzarella 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 cheeses that have 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.

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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