What is Cheese Mold?

Mold is a type of fungus that grows on various foods, including cheese. While mold on most foods signals spoilage, certain types of mold are essential for making some cheese varieties.

What is Cheese Mold

When you think of mold, you probably picture the fuzzy green or white growth that appears on old bread, fruit or leftovers. This kind of mold is a sign of spoilage and means the food should be discarded.

However, for some types of cheese, mold is an intentional ingredient that helps create unique flavors, aromas, and textures.

What is Cheese Mold?

Cheese is made by curdling milk with enzymes to separate the curds from the liquid whey. The curds are then pressed, salted, and aged.

Mold refers to certain fungi that are intentionally introduced during cheese production to promote characteristic textures, appearances, and flavors.

The most common cheese molds are species of Penicillium, including:

  • Penicillium roqueforti - Used in blue cheeses
  • Penicillium candidum - Creates the white rind on Brie and Camembert
  • Penicillium camemberti - Also used in soft-ripened cheeses like Camembert

As these molds grow, they produce enzymes that break down proteins and fats in the cheese into smaller molecules. This helps develop the unique taste and aroma of mold-ripened varieties.

The key difference between intentional cheese molds versus unintentional molds is that the former are added deliberately under controlled conditions. Undesirable molds show up due to improper food handling and storage.

Which Cheeses Are Made with Mold?

There are two main types of mold-ripened cheese: internally ripened and externally ripened.

Internally ripened cheeses have spores mixed directly into the cheese curds before pressing. As they mature, these spores germinate to create mold growth inside the cheese.

Blue cheeses are the prime example, including Roquefort, Gorgonzola, Stilton, and Danish Blue. They’re inoculated with Penicillium roqueforti, which grows to form the characteristic blue-green veining throughout the interior.

During aging, long stainless steel needles are used to pierce blocks of the cheese in various places. This allows air to penetrate and feed the mold growth.

On externally ripened cheeses, mold spores are only on the rind or outer layer. These fungi break down proteins and fats close to the cheese's surface, resulting in gooey textures and richer flavors in the underlying paste.

Classic examples are the white-crusted soft cheeses like Brie and Camembert. These are inoculated with mold powders containing Penicillium camemberti and Penicillium candidum.

As the fungi consume lactose and proteins near the rind, the cheese interior becomes creamier and takes on earthy, mushroom notes. The mold growth on these cheeses is managed by washing or brushing to prevent overgrowth.

There are also semi-soft washed rind cheeses ripened by “smear cultures” from older cheeses. And naturally moldy hard cheeses like Lincolnshire Poacher maintain their firm texture thanks to low-moisture content.

Here is a quick overview of common mold-ripened cheese categories:

Cheese TypeCommon Molds UsedExamples
Blue cheesePenicillium roquefortiGorgonzola, Stilton
Soft-ripenedPenicillium candidumPenicillium camembertiBrie, Camembert
Washed rindSmear culturesTaleggio, Époisses
Natural rindMixture of ambient moldsLincolnshire Poacher

Intentional cheese molds produce enzymes that break down fats and proteins. This helps create the distinct aromas, flavors and textures in mold-ripened varieties.

Is Moldy Cheese Safe to Eat?

Now that you know why molds are used in some types of cheese production, you may be wondering if all moldy cheese is safe.

Mold on external surfaces of properly made blue cheese and bloomy rinds is edible. These fungi are carefully regulated during aging to achieve ideal ripeness.

However, if unfamiliar colors, fuzziness or spots appear in these cheeses, it warrants caution - especially for individuals with weakened immune function or mold allergies. Never eat cheese with black, pink or bright neon mold as toxins may be present.

For solid cheeses like cheddar, Swiss or gouda, white and blue-green molds are fairly common. If these growths are limited to the outer layer, simply trim off at least 1 inch around and below the mold. The dense, low-moisture interior prevents deep penetration in harder styles.

The big exception here is soft mouldable cheeses including cottage cheese, cream cheese, fresh goat cheese, ricotta and shredded mozzarella. These have higher moisture content and looser textures that allow molds to rapidly spread. Any sign of mold in soft or crumbled cheese means you should discard the entire batch.

Likewise, cheeses made from unpasteurized (raw) milk also tend to have high moisture. Take extra care inspecting these for even small mold spots.

Hard cheeses can be salvaged by cutting out moldy parts, but soft varieties should go straight in the trash!

Key Takeaway: Soft moldable cheeses with any mold present should be fully discarded. Hard cheeses can have moldy sections removed.

Below are some other good guidelines for identifying bad moldy cheese:


  • Black, pink, neon or brightly colored mold (may contain mycotoxins)
  • Thick mold growth covering large areas
  • Cheese liquefying or with an unusual color


  • Strong unpleasant, sour or rotting odor
  • Ammonia smell


  • Cheese feels slimy
  • Presence of hollow air pockets or soft spots

Trust your senses! If cheese exhibits multiple red flags or just seems off despite no visible mold - when in doubt, throw it out.

Dangers of Eating Moldy Cheese

You might be wondering...what exactly is the harm in eating cheese contaminated with unregulated mold growth?

Firstly, harmful bacteria like listeria, salmonella and E. coli often accompany unwanted mold infestations. These can lead to severe gastrointestinal illness.

Additionally, dangerous molds can produce toxic chemicals known as mycotoxins. Roquefortine C is one commonly associated with cheeses but various mycotoxins exist.

Consuming high levels of mycotoxins may cause acute toxicity and death. Long-term, low-level exposure has been potentially tied to cancer, organ damage, hormone disruption, and immunosuppression

Vulnerable populations including children, pregnant women, elderly and immunocompromised individuals face the highest risks from ingesting mycotoxins. But even healthy adults can experience adverse reactions.

The good news is you aren’t likely to keel over after nibbling a tiny moldy spot on cheddar! However, severe toxicity has occurred in developing countries after consuming heavily molded grain products.

Cheese has far lower risks given higher food standards. But why chance it when moldy sections can easily be cut away?

In general, healthy adults cutting out visible mold growth on hard cheeses have minimal cause for concern. For vulnerable groups, avoiding moldy cheeses altogether is the best approach.

How to Prevent Moldy Cheese

Preventing mold on cheese comes down to two key factors: proper storage and avoiding cross-contamination.

Here are some cheese storage tips to inhibit mold growth:

  • Wrap tightly in plastic wrap or wax/parchment paper to limit oxygen. Many experts recommend doubled up layers.
  • Use breathable containers like cheese paper or specialized box with ventilation.
  • Monitor humidity - the vegetable crisper drawer in fridges often works well.
  • Maintain cooler temperatures between 35° to 40°F. Avoid temperature fluctuations.

In addition:

  • Designate one cutting board only for cheese. Never cut other foods on the same surface raw meat touched.
  • Wash hands and utensils thoroughly before and after handling cheese to prevent transferring molds.
  • Use clean cheese plane or knife when portioning. Don’t dig around inside cheese with contaminated fingers.
  • Keep refrigeration organized so moldy produce doesn’t cross-contaminate.

Key Takeaway: Proper storage and avoiding cross-contamination is crucial to prevent unwanted mold growth on cheese.


Is it safe to eat blue cheese with white mold on it?

White mold growth is normal on the natural rinds of some blue cheeses. As long as the cheese still tastes, smells and feels firm underneath, it is generally safe to eat. Simply use a clean knife to slice below this rind mold. However, thick widespread growth or unfamiliar colors warrant discarding it.

Can you freeze cheese with mold on it to kill mold?

Freezing may stop mold from spreading further. However, toxins from molds can withstand freezing temperatures. Any soft or crumbly cheese showing mold should be discarded rather than frozen. Hard cheeses may be salvaged by cutting away all moldy areas then freezing. But freezing can negatively impact texture.

If I’m pregnant, is it OK to eat blue cheese?

According to the CDC, pregnant women should completely avoid soft mold-ripened cheeses like Brie. Hard cheeses like cheddar and semi-soft blue cheese you cook are safer. However, uncooked blue cheese still poses a small listeria infection risk. Exercise caution and check if your doctor has guidance on consumption.

Can I get sick hours after eating moldy cheese?

Yes, it’s possible to experience delayed symptoms. Mild to moderate symptoms normally occur within hours up to 2-3 days after ingesting mycotoxins or harmful mold-related bacteria. But onset timing depends on the type of infection/toxin and individual sensitivity. Monitor closely for fever, nausea and diarrhea in the days following consumption of questionable cheese.

Is mold ever beneficial in cheesemaking?

Yes! As outlined earlier, certain Penicillium molds are intentionally used to produce signature flavors and appearances in blue cheeses, Brie, Camembert and other varieties. These highly regulated fungi generate enzymes causing controlled breakdown of proteins and fats over time. Without mold growth, we’d lack some of the cheese world’s greatest hits!


While mold might seem like the last thing you want near food, it’s essential for making certain cheese specialties like Roquefort and Brie.

Controlled mold growth helps form the signature flavors, textures and colors in blue-veined, bloomy and washed rind cheeses. These fungi produce metabolic enzymes and acids that break down cheese components over time through a process called ripening.

AGAH Productions
AGAH Productions