The Sensory Inspection: What to Look, Smell, and Feel For
Determining if cheese is contaminated is primarily a sensory task, but it requires practice and a discerning eye. Not all cheese is created equal, and what signals spoilage in one might be a hallmark of quality in another. The key is to know what is normal for your specific type of cheese and to react appropriately to anomalies.
Look for Visual Cues
- Unexpected Mold: While blue cheeses and bloomy-rind varieties like Brie or Camembert feature intentional, safe mold, any new, fuzzy growth is a major red flag. Mold on soft, fresh, or shredded cheese is a sign to discard the entire product. For hard cheeses, you may be able to trim the mold away safely. Be especially wary of black, pink, or orange mold, which can produce harmful toxins and should lead to immediate disposal of the entire cheese.
- Discoloration: The color of cheese should be consistent. Significant darkening, yellowing, or browning can indicate spoilage. A pink or orange slime on the rind of semi-hard cheeses suggests bacterial or yeast spoilage.
- Other Surface Changes: Look for excessive moisture, like a pool of milky liquid around soft cheese, or a slimy film on the surface of any type of cheese.
Perform the Smell Test
- Off-Putting Odors: A characteristic aroma is normal for many cheeses, but you should be cautious of a smell that is excessively sour, rancid, or ammonia-like. A mild cheese that suddenly smells strong and pungent is likely spoiled. For naturally smelly cheeses, a bad sign is an unusually concentrated or overpowering aroma, sometimes described as similar to cat urine.
Check the Texture
- Slimy or Sticky: A tacky or slimy film on the surface indicates bacterial spoilage and should be discarded.
- Overly Dry or Crumbly: If a creamy or semi-soft cheese becomes hard, dry, or unusually crumbly, it has likely gone past its prime.
- Grainy: A grainy texture on a cheese that is normally smooth can indicate spoilage or that it has been frozen and thawed incorrectly.
Hard vs. Soft Cheese: Rules for Handling Spoilage
Different cheese types respond differently to contamination, largely due to their moisture content. Soft cheeses, with their higher moisture, are more hospitable to harmful bacteria, which can spread quickly and invisibly throughout the product. Hard cheeses, being drier and denser, are more resistant to deep penetration by mold spores.
| Feature | Hard Cheese (e.g., Cheddar, Parmesan) | Soft Cheese (e.g., Brie, Ricotta) |
|---|---|---|
| Visible Mold | Visible mold on the surface can be cut off. | Discard the entire product immediately. |
| Cutting | Trim at least 1 inch (2.5 cm) around and below the moldy spot, keeping the knife clean. | The high moisture allows mold roots and harmful bacteria to spread throughout. |
| Slime or Stickiness | A slimy rind is a sign of spoilage. Discard. | Slimy texture indicates contamination. Discard immediately. |
| Bacterial Risk | Lower risk of deep bacterial penetration. | Higher risk of harmful bacteria like Listeria propagating throughout the product. |
| Shelf Life | Months (unopened), weeks (opened). | Weeks (unopened), 5-7 days (opened). |
Preventing Contamination Through Proper Storage
To maximize the life of your cheese and minimize contamination risk, follow these storage best practices:
- Refrigerate Properly: Store all natural cheeses in the refrigerator, ideally between 34–38°F (1–3°C). Use a dedicated deli drawer or a separate, sealed container to prevent odor absorption and cross-contamination.
- Use Breathable Wraps: Avoid tightly sealing aging cheeses in plastic wrap. Plastic traps moisture, creating a perfect environment for mold. Instead, use cheese paper, parchment paper, or wax paper, and then place the wrapped cheese in a partially sealed plastic bag or container to maintain a balance of humidity.
- Avoid Cross-Contamination: Always use clean utensils and cutting boards when handling cheese. If cutting a moldy section from a hard cheese, use a different knife for the clean portion. Never use the same knife for raw meat or produce.
- Beware of Raw Milk Cheeses: Cheeses made from unpasteurized milk can pose a higher risk of bacterial contamination from pathogens like Listeria, E. coli, and Salmonella. High-risk groups, including pregnant women, the elderly, and immunocompromised individuals, should generally avoid these cheeses.
Conclusion: When in Doubt, Throw It Out
In the end, recognizing contaminated cheese is a multi-faceted process that relies on a combination of visual, olfactory, and tactile cues. By understanding the key differences between hard and soft cheeses and practicing safe storage, you can protect yourself from foodborne illnesses. Remember the golden rule of food safety: if any aspect of the cheese—its appearance, smell, or texture—seems unusual or questionable, it's safest to discard it immediately rather than risk getting sick. An authoritative resource on general food safety can be found at the USDA Food Safety and Inspection Service.
