How to Tell If Cheese Is Bad
Hard cheese like cheddar or Parmesan is bad if it smells ammonia-like or sour, is slimy, or has pink or widespread mold. For small mold spots you can cut at least 1 inch around and below the spot, and hard cheese keeps 3 to 6 weeks after opening.
Signs Cheese has gone bad
- Ammonia or sour smell. Aged cheese smells nutty and sharp, but a harsh ammonia or sour milk odor beyond its usual smell shows it's gone over.
- Slimy surface. Hard cheese should be dry to the touch. A slick or sticky coating is bacterial growth, not normal aging.
- Widespread or pink/orange mold. A small spot can be cut away from hard cheese, but mold that has spread across the surface, or any pink, orange, or black growth, means the block should go.
- Hard, dry, cracked texture. Cheese that is dried out and cracking has lost its moisture and flavor. It's a quality issue first, but combined with off smells, discard it.
- Bitter, unpleasant taste. If a thin slice tastes soapy or harshly bitter, it's past its best. Spit it out.
Looks weird, but it's fine
- White crystals in aged cheese. Crunchy white specks in aged cheddar or Parmesan are tyrosine or calcium lactate, which are signs of aging and flavor. They're safe.
- Small surface mold on hard cheese. On hard cheese only, cut off at least 1 inch around and below the spot, keeping the knife out of the mold, then rewrap in fresh wrap.
- Sweating or oil beads. Beads of fat on the surface come from temperature changes. Blot with a paper towel; the cheese is fine.
How long does Cheese last?
| Where | How long | Note |
|---|---|---|
| Fridge (unopened, hard) | 6 months | Sealed block |
| Fridge (opened, hard) | 3 to 4 weeks | Wrap tightly after each use |
| Freezer | 6 months for best quality | Texture turns crumbly; best for cooking |
| Counter | Max 2 hours | Fine for a cheese board, then back in the fridge |
How to store it
- Wrap cheese in wax paper or cheese paper and then loosely in plastic so it can breathe without drying out.
- Use a clean knife each time, since crumbs and touches from other foods spread mold.
- Freeze hard cheese in portions if you won't finish it, and plan to use it for cooking.
Use it up before it turns
Frequently asked questions
Can you cut mold off cheese?
For hard cheeses like cheddar and Parmesan, yes. Cut at least 1 inch around and below the mold spot without touching the mold with the knife. Never do this with soft, shredded, or sliced cheese.
What are the white spots on my cheddar?
Usually tyrosine or calcium lactate crystals, which form in well-aged cheese and are harmless. If the spots are fuzzy rather than crunchy, it's likely mold.
Does hard cheese expire?
Yes, but slowly. Opened hard cheese keeps about 3 to 4 weeks in the fridge when well wrapped. Look and smell before you serve it.
More food freshness guides
General guidance based on USDA FoodKeeper. Storage times are estimates and conditions vary. When in doubt, throw it out.