How do I know if blue cheese has gone bad?

October 22, 2025 •

3 min read

While blue cheese is intentionally molded with Penicillium roqueforti for its distinct flavor, not all molds are welcome. Determining if blue cheese has gone bad requires a keen eye and nose, as spoilage can occur even with this famously pungent food.

Quick Summary

This guide explains the visual, olfactory, and textural clues for determining if blue cheese is spoiled, detailing the difference between beneficial and harmful mold growth. It covers signs like excessive ammonia smell, pink or black discoloration, and slimy texture, providing clear criteria for when to discard the cheese.

Key Points

Unusual Mold: Look for fuzzy, dark, white, or pink mold, which differs from the blue-green veins of healthy blue cheese.
Excessive Ammonia Smell: A normal hint of ammonia is fine, but an overwhelmingly strong, acrid odor means the cheese has spoiled.
Slimy or Sticky Texture: A slick, slimy surface or excessively mushy consistency indicates bacterial growth and spoilage.
Discoloration of the Cheese Body: The creamy white cheese should not show brown, pink, or unusual green tints beyond the moldy veins.
Pooled Liquid: Excessive moisture or liquid at the bottom of the container signals that the cheese is breaking down.
Discard Soft Cheese: Unlike hard cheeses, you should not cut off and salvage a piece of soft blue cheese that shows signs of spoilage; throw it all away.

Visual Clues: Spotting Unwanted Mold and Discoloration

Unlike hard cheeses, where you can often trim away a small patch of unwanted mold, blue cheese is a soft cheese, and any signs of non-standard mold mean it should be discarded. The mold that creates the blue veins is deliberately introduced and controlled during aging. However, other molds and yeasts can grow and contaminate the cheese after it's opened and exposed to your home environment.

What to Look For:

Fuzzy, Dark Mold: The most obvious sign of spoilage is the presence of fuzzy, grey, white, or black mold on the cheese's surface. The desirable mold inside the cheese appears as smooth, blue or greenish-blue veins.
Pink or Yellow Spots: Pink or yellow patches on the surface are often a sign of unwanted yeast, which can indicate that the cheese is no longer safe to eat. These are a definite red flag for spoilage.
Discolored Cheese Body: The creamy white or yellowish body of the cheese should not have major discoloration. If you notice it turning brown, green, or pink beyond the intended veins, it's a sign that unwanted bacteria are taking over.
Excess Moisture: Excessive moisture or liquid pooling inside the packaging is often a sign that the cheese is degrading. This indicates that the delicate balance of the cheese's composition has been compromised.

Olfactory and Textural Indicators of Spoilage

With blue cheese, a powerful, pungent smell is normal, but a change in that smell is a key indicator of spoilage. The same goes for texture; a little softness is normal, but drastic changes point to a problem.

The Smell Test: Ammonia and Sourness

Excessive Ammonia: A slight whiff of ammonia is not uncommon in blue cheese, especially when freshly unwrapped. However, if the ammonia smell becomes overwhelmingly strong, like a household cleaner or cat urine, it’s a clear sign the cheese has gone bad.
Musty or Sour Odor: Beyond ammonia, a distinctly sour or musty smell that is different from the usual blue cheese aroma means spoilage has occurred.

The Texture Test: Slime and Grittiness

Slimy or Sticky Surface: The surface of blue cheese should be relatively firm or moist, but if it develops a slimy or sticky film, it is spoiled and should be discarded. This indicates bacterial growth on the surface.
Excessive Softness or Grittiness: While some blue cheeses are soft and crumbly, an overall breakdown into a mushy or gritty consistency is a sign of decomposition. The cheese is breaking down in an uncontrolled way.

Bad Blue Cheese vs. Good Blue Cheese


Indicator	Good Blue Cheese	Spoiled Blue Cheese
Appearance	White, creamy base with blue or green veins. Veins are integrated into the cheese.	Fuzzy, white, grey, or black surface mold. Pink or yellow spots of yeast. Discolored or off-colored cheese body.
Smell	Pungent, earthy, and sometimes slightly ammoniated when unwrapped.	Overpowering, strong ammonia smell, sour, or musty odor.
Texture	Firm, moist, and crumbles predictably.	Slimy or sticky surface. Excessively mushy, soft, or gritty.
Liquid	Minimal to no liquid in the packaging.	Noticeable pooling of brownish or clear liquid.

Proper Storage is Key

To extend the life of your blue cheese and prevent spoilage, proper storage is crucial. For the best results, use cheese paper, or if unavailable, wrap the cheese first in parchment or wax paper before placing it in a loose plastic bag or foil. This allows the cheese to breathe without drying out. Store it in the vegetable drawer of your refrigerator, which typically has more stable humidity. Avoid tightly sealing it in plastic wrap alone, as this can negatively affect the flavor. Blue cheese crumbles spoil more quickly than a solid wedge, usually within about a week after opening.

Conclusion

Understanding how to know if blue cheese has gone bad hinges on observing changes in its normal state. While it's a moldy cheese by design, key changes in appearance, texture, and smell will signal that it has crossed the line from deliciously pungent to spoiled and potentially harmful. Trust your senses: discard the cheese if you find fuzzy mold, pink or yellow discoloration, a strong ammonia odor, or a slimy texture. When in doubt, it is always safer to throw it out to avoid foodborne illness.

For more in-depth information on food safety, visit the FDA website.

Frequently Asked Questions

No, because blue cheese is a soft, high-moisture cheese, harmful bacteria and mold roots can spread easily throughout the entire piece, even if visible mold is only on the surface. For safety, you must discard the entire piece.

Good mold is the intentional blue or green veining of Penicillium, which is integrated into the cheese and not fuzzy. Bad mold is typically fuzzy, darker in color (grey, black, or white), or appears as slimy pink or yellow spots.

A mild, slightly ammoniated scent can be normal, especially when the cheese is first opened. However, an extremely strong, acrid, or pungent ammonia odor is a sign of spoilage, and the cheese should be discarded.

To prevent spoilage, wrap blue cheese in parchment or wax paper, followed by a loose layer of foil or a slightly vented plastic bag, and store it in the refrigerator's vegetable drawer. This allows it to breathe without drying out.

Yes, blue mold spores can travel through the air and contaminate other foods. Store blue cheese separately and ensure it is properly wrapped to prevent cross-contamination.

Consuming spoiled blue cheese can cause food poisoning, leading to symptoms like nausea, vomiting, and diarrhea. Harmful molds may also produce mycotoxins, which can have negative health effects.

After opening, blue cheese crumbles should be used within about a week, while a solid wedge can last for one to two weeks with proper storage. However, always check for signs of spoilage before consuming.