Is it safe to eat expired grated Parmesan cheese?

Parmesan cheese is a hard Italian cheese made from cow’s milk that is a staple ingredient in many dishes. It has a rich, nutty flavor and distinctive granular texture that makes it perfect for grating and sprinkling. Pre-grated Parmesan cheese is very convenient and commonly found in the refrigerated section of grocery stores. However, Parmesan cheese, especially pre-grated varieties, have a relatively short shelf life compared to hard cheeses sold in blocks. So what happens if you discover an expired jar of grated Parmesan in the back of your fridge? Is it still safe to eat? Let’s take a closer look at how to know if your grated Parmesan cheese is still good after the expiration date.

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What is the shelf life of grated Parmesan cheese?

The shelf life of pre-grated Parmesan depends on how it is packaged and stored. Here are some general guidelines for Parmesan shelf life:

Unopened, shelf-stable grated Parmesan in a can or plastic container can last 10 months to 1 year past the “best by” date on the package.

Once opened, an airtight container of shelf-stable grated Parmesan will last 3 to 4 weeks in the refrigerator.
Vacuum-sealed grated Parmesan, either refrigerated or not, will last about 6 to 8 months.
Tightly wrapped Parmesan wedges or blocks can keep for over 1 year in the fridge.

Grated Parmesan in the dairy/deli section lasts about 2 weeks after opening when properly stored.
Homemade grated Parmesan stored in an airtight container will last around 4 months in the fridge or freezer.

As you can see, there is quite a bit of variability. Properly stored, unopened grated Parmesan has the longest shelf life, while freshly grated Parmesan from the deli section has the shortest.

How to tell if grated Parmesan cheese is spoiled

Grated Parmesan can grow mold or bacteria over time, making it unsafe to eat. Here are some signs that your Parmesan cheese is expired and should be discarded:

There is visible mold on the cheese.
The cheese has an off smell, like sour milk or ammonia.

The texture has become grainy or feels slimy.
The cheese has noticeable discoloration or green/black spots.
The cheese crumbles instead of grating.

You see signs of moisture or liquid in the packaging.

If your grated Parmesan exhibits any of these characteristics, it’s best to throw it out. Don’t simply scrape off mold and continue eating the cheese. Mold can penetrate deep into the product even if you can’t see it.

What causes grated Parmesan cheese to go bad?

There are a few reasons why grated Parmesan doesn’t stay fresh indefinitely:

Microbial growth: Like any dairy product, Parmesan can grow spoilage microorganisms like molds, yeasts, and bacteria over time. This is accelerated by oxygen, light, and warmth. Mold in particular can dig deep into hard cheeses.
Fat oxidation: Exposure to oxygen causes the fats in the cheese to oxidize and become rancid. This changes the flavor.
Moisture loss: As it dries out, grated Parmesan can become crumbly and discolored. Hard cheeses need moisture to maintain their trademark texture.

Enzyme activity: Residual enzymes like lipases in the cheese continue to break down fats and proteins during storage. This alters the quality and flavor.
Contamination: Bits of old, spoiled cheese clinging to graters or containers can cross-contaminate fresh product.

Proper storage helps slow these processes, but they will eventually cause the cheese to deteriorate.

Is it dangerous to eat expired Parmesan cheese?

Eating small amounts of expired grated Parmesan that has been stored properly is unlikely to make you sick. Hard cheeses like Parmesan are less perishable than soft cheeses due to their lower moisture content and acidity.

That said, there are some food safety risks to be aware of:

If mold is visible, eating the cheese could result in gastrointestinal distress or allergic reactions.

Listeria or pathogenic bacteria like staphylococci, salmonella, and E. coli can grow on spoiled cheeses and cause severe illness.
Cheeses made from unpasteurized milk are more prone to bacteria especially when aged over 60 days.
Storage conditions like humidity can increase the risks even in harder cheeses like Parmesan.

So while a freshly expired Parmesan probably won’t make you sick after the sell-by date, you shouldn’t take risks with cheese that is growing mold or has an unpleasant odor. When in doubt, remember the old adage “When in doubt, throw it out.”

Tips for storing Parmesan cheese

To get the longest possible shelf life out of your grated Parmesan, store it properly:

Keep Parmesan tightly sealed in its original packaging or an airtight container.

Once opened, rewrap the Parmesan tightly in plastic wrap or place in a resealable plastic bag.
Make sure the cheese doesn’t have much air exposure.
Store grated Parmesan away from light sources, like sunlight or refrigerator bulbs.

Keep Parmesan in the refrigerator drawer, not in the door where temperature fluctuates.
Place the Parmesan in the back of the fridge where temperature is most stable.
Avoid introducing moisture into the product. Use clean, dry utensils.

Don’t mix old and new product in the same container.

With proper storage and handling, you can enjoy grated Parmesan for many months past the printed expiration date on the package. But when in doubt, remember it’s better to be safe than sorry.

How to store Parmesan wedges and blocks

Storing Parmesan in wedge or block form can extend its shelf life. Here are some tips:

Leave Parmesan in its original packaging until you are ready to use it. The cryovac plastic protects the cheese.
Once opened, tightly rewrap the cheese in plastic wrap, wax paper, or parchment. Make sure the cheese is completely sealed with no air gaps.
You can also use an open plastic bag pressed around the cheese to keep air out.

Store in the refrigerator cheese drawer for up to 4 months.
For longer storage, you can double wrap the cheese in plastic and then foil and freeze it for 6-8 months.
Avoid freezing and thawing repeatedly as this causes texture changes.

Keep the surface of the cheese as dry as possible to prevent mold growth.
Cut off at least 1 inch around and below any moldy areas on hard cheese before eating.

With airtight packaging, Parmesan wedges and blocks can keep well in the fridge or freezer. However, watch for signs of spoilage like mold especially along the rind. When stored properly, Parmesan cheese can retain its delicious flavor long past the use-by date.

Can you freeze grated Parmesan cheese?

Yes, it’s perfectly safe to freeze grated Parmesan cheese for extended storage. Here are some freezing tips:

Make sure any cheese you freeze is fresh and hasn’t expired.
Freeze grated cheese in an airtight container or heavy-duty freezer bag. Squeeze out excess air.

Place wax paper between layers of grated cheese in a container to prevent it from freezing into a solid block.
Add a bit of cornstarch, about 1 teaspoon per cup of cheese, to help prevent clumping and keep it free-flowing when thawed.
Lay bags flat in the freezer to keep the cheese spread out in a thin layer.

Label bags with the date so you know how long it’s been frozen.
Use frozen grated Parmesan within 6 to 8 months for the best quality.

Thawed grated Parmesan may be slightly drier in texture but will be safe to consume. Let the cheese defrost fully in the refrigerator before using. Frozen Parmesan is great to have on hand for recipes, pizza, pasta, or garnishes.

What happens if you eat moldy Parmesan cheese?

It’s generally not recommended to eat moldy Parmesan cheese. Here’s why:

Hard cheeses like Parmesan are more prone to developing hidden mold inside although not visible on the surface.
Inhaling mold spores from contaminated cheese can trigger respiratory allergic reactions or asthma attacks in sensitive individuals.

Eating moldy cheese may cause symptoms like nausea, vomiting, diarrhea, and other gastrointestinal issues.
Certain molds like penicillium roqueforti used in blue cheeses produce toxic byproducts that can cause illness if contamination spreads.
Cheese molds and mycotoxins can be very hardy and may not be destroyed by cooking. Freezing also may not deactivate mold.

While a small amount of mold isn’t likely dangerous for most healthy adults, it’s better to be cautious. Cut off at least 1 inch around and below the moldy spot and discard the rest. With an expensive, aged cheese like Parmesan, it’s not worth taking risks. When in doubt, play it safe and throw it out.

Can you eat Parmesan cheese rind?

The outer rind that forms on wedges or blocks of Parmesan is completely edible and safe to eat. Here are some facts about eating Parmesan rind:

The natural rind is a combination of hardened cheese and yeast mold that develops as it ages.

It contains high concentrations of flavorful amino acids like glutamate and adds a unique tang and texture.
The rind is very low in fat and carbohydrates compared to the interior cheese.
It provides a good source of calcium and other nutrients found in the actual cheese.

The rind can be eaten as-is but is often simmered in sauces, soups or rice dishes to add cheesy umami flavor.
Don’t eat rind that is growing blue, green or black mold. Cut off any discolored areas.

In general, the Parmesan rind offers a unique way to add nutritious flavor. Just be sure to remove any molded portions before eating it. With good storage, the natural rind can be safely consumed even after the inner cheese has expired.

Conclusion

So back to our original question – can you safely eat expired grated Parmesan cheese? The answer is that it depends. Properly stored, unopened Parmesan can often last for months or even years past its printed date. But once opened, grated Parmesan has a shorter shelf life of only a few weeks to months.

Check the cheese for signs of spoilage like mold, off-colors, bad odors, or texture changes. Make sure it was stored in airtight packaging in the fridge. Then do a small taste and smell test. While not extremely hazardous, there is some risk of foodborne illness from microorganisms in spoiled, aged cheeses. This is especially true for people with compromised immunity.

Your best bet is to buy grated Parmesan in smaller quantities that can be used up quicker. And store any leftover product in an airtight container in the back of the refrigerator to extend its shelf life as long as possible. But when in doubt, remember it’s better to err on the side of caution and discard any expired cheese with odd smells or appearance. The possible stomach upset and lost dollars are not worth risking your health.