How do you know when fresh Parmesan is bad?

Parmesan cheese, known for its distinct flavor and hard texture, is a staple ingredient in many recipes. However, even properly stored Parmesan has a relatively short shelf life compared to other hard cheeses. Knowing when your Parmesan has gone bad can help you avoid consuming spoiled cheese and wasting food.

Here are quick answers to common questions about determining if your Parmesan cheese is spoiled:

How can you tell by smell?

Fresh Parmesan should have a sweet, nutty aroma. If the smell is unpleasant, strong, or ammonia-like, the cheese is likely bad.

How can you tell by look?

Look for mold, sliminess, dryness, or unusual crystallization on the cheese. Signs of spoilage like these indicate it should be discarded.

How long does Parmesan last when unopened?

Properly stored, unopened Parmesan will generally last past the “best by” date, usually at least 12 months in the fridge.

How long does grated Parmesan last after opening?

An opened package of grated Parmesan will stay fresh for 1-2 months in the fridge. Smaller pieces have more surface area exposed to air, causing it to spoil faster.

Can you freeze Parmesan cheese?

Yes, Parmesan can be frozen to extend its shelf life. Make sure to wrap it properly in plastic wrap and foil. It can be kept frozen for up to 9 months.

What are the signs of spoiled Parmesan?

The most common signs that your Parmesan has gone bad are mold growth, an unpleasant or “off” smell, changes in texture, and an unnatural coloration or crystallization on the cheese.


Parmesan cheese has a relatively short shelf life compared to other hard cheeses. With proper storage in the refrigerator, Parmesan should stay fresh for 1-2 months past its printed expiration date. However, there are several clear signs that indicate your Parmesan has spoiled and should be discarded. These include mold, unpleasant odors, changes in texture, and odd colors or crystals forming on the cheese. Knowing what to look for can help you avoid consuming rancid Parmesan. If you notice any of these red flags, it’s safest to throw the cheese out.

What is Parmesan Cheese?

Parmesan cheese is a hard Italian cheese made from cow’s milk. It has a granular texture and intense, nutty umami flavor. True Parmesan comes from the Parma region of Italy and is produced according to strict production guidelines. It is also known as Parmigiano-Reggiano.

Parmesan is used grated or shredded as a topping for pastas, salads, soups, and pizzas. It also works well when melted into risottos or baked dishes. Both domestic and imported Parmesan is available at most grocery stores.

Key Characteristics:

  • Hard, granular texture
  • Pale yellow color
  • Sharp, nutty, and salty flavor
  • Aged 1-2 years or more

How is Parmesan Cheese Made?

Authentic Parmesan cheese is made from raw cow’s milk according to strictly regulated procedures in the Parma region of Italy. Here is an overview of the traditional production process:

1. Curdling the Milk

Rennet is added to heat-treated milk to cause curdling. This separates the milk solids from the liquid whey.

2. Cutting the Curds

The curd is cut into small pieces to release more whey, forming semi-soft curds.

3. Heating and Pressing the Curds

The curds are heated, stirred, and pressed to extract excess moisture and form a unified mass.

4. Molding the Cheese

The cheese is molded into large wheels and the rind is stamped with the production information.

5. Aging the Cheese

Wheels are aged 1-2 years to develop the distinctive Parmesan flavor and texture.

6. Inspection and Sale

Wheels are inspected for quality and sold whole or grated.

How to Store Parmesan Cheese

Proper storage is key to maximizing the shelf life of Parmesan cheese. Here are some tips for storing Parmesan correctly:

For a wedge or block:

  • Wrap tightly in plastic wrap or parchment paper.
  • Place in a resealable plastic bag, removing excess air.
  • Store in the refrigerator for up to 2 months.

For grated Parmesan:

  • Keep in an airtight container.
  • Refrigerate for up to 1-2 months after opening.
  • For longer storage, freeze in an airtight bag for up to 9 months.

General tips:

  • Minimize exposure to air to avoid mold.
  • Keep Parmesan away from high-moisture foods that can cause sogginess.
  • Store in the coldest part of the refrigerator, not the door.

How to Tell if Parmesan Cheese Has Gone Bad

Parmesan cheese can grow harmful molds before showing obvious signs of spoilage. But there are several clear indicators that your Parmesan is past its prime and should be discarded.


Perhaps the most obvious sign of spoiled Parmesan is mold. Cheese kept past its prime can develop fuzzy whitish or greenish mold. If you see mold growing on hard Parmesan cheese, do not try to cut it off – the spores penetrate the cheese. Any Parmesan with mold present should be discarded.


Fresh Parmesan has a sweet, nutty aroma. An unpleasant, strong, or ammonia-like smell indicates spoilage. Trust your nose – if your Parmesan smells “off,” it is likely bad.


Parmesan is hard with a granular texture when fresh. Soft spots, sliminess, or a gooey texture means the cheese is past its prime.


Discoloration, dryness, or odd crystallization on the cheese can be a sign of spoilage. Normal Parmesan has an ivory to pale yellow hue.

Expiration Date

The “best by” date is a helpful guide, though Parmesan can often last 1-2 months past that date when stored properly. But if your cheese is past its date by over 3-4 months, it’s best to be cautious and toss it out.

How Long Does Parmesan Cheese Last?

When stored properly, Parmesan cheese typically lasts:

Parmesan type Unopened After opening
Wedge, block 12 months 2-4 weeks
Pre-grated 8-10 months 1-2 months
Frozen 12 months 1-2 months

However, signs of spoilage are a better indicator of freshness than the “best by” date. Inspector your Parmesan and rely on your senses – if it looks or smells off, err on the side of caution and throw it out regardless of the date.

What Happens If You Eat Spoiled Parmesan?

Eating small amounts of spoiled Parmesan is unlikely to cause serious illness in healthy adults. However, consumption of large quantities can cause food poisoning symptoms like:

  • Nausea
  • Vomiting
  • Diarrhea
  • Stomach cramps
  • Headache

The harmful bacteria and molds found in spoiled dairy products can be especially dangerous for those with weakened immune systems, the very young, and the elderly.

If Parmesan has been left unrefrigerated for over 2 hours, it is safest to discard it even if no signs of spoilage are visible. Bacteria like staphylococcus aureus can begin growing at room temperature and produce toxins that are not destroyed by cooking. When in doubt, throw it out.

How to Use Up Parmesan Before It Spoils

To avoid wasting Parmesan that is close to expiring, here are some delicious ways to use it up:


  • Grate over pasta, risottos, and pizzas
  • Add to casseroles, gratins, and baked pastas
  • Mix into meatballs or breadcrumb coatings
  • Stir into vegetable dips and spreads


  • Fold into biscuit or scone dough
  • Sprinkle over breads before baking
  • Mix into cheese crackers or straws
  • Blend into cheese crisps or cheese balls


  • Pair with wine, fruits, and nuts
  • Drizzle with honey for an appetizer
  • Stack in sandwiches or paninis
  • Top salads, bruschetta, and crostini

Getting creative with recipes can help use up Parmesan before it goes bad. Even if slightly dried out, it adds excellent flavor to many dishes.

How to Freeze Parmesan Cheese

Freezing is an effective way to extend the shelf life of Parmesan cheese for later use. Here is a simple process for freezing Parmesan correctly:

  1. Start with fresh, packaged cheese within 2 months of purchase.
  2. Cut into usable portions if freezing a block.
  3. Wrap tightly in plastic wrap, squeezing out air.
  4. Place in a freezer bag or airtight container.
  5. Label bag with name and freeze-by date (up to 9 months).
  6. Freeze at 0°F or below.
  7. Thaw refrigerated overnight before use.

Grate or shred Parmesan before freezing for easier use after thawing. Frozen Parmesan may become crumbly or dry once thawed but is still good for cooking. It can be frozen longer than refrigerated, for up to 9 months, without compromising quality or safety.

Tips for Freezing Parmesan

  • Avoid repeated freeze-thaw cycles by only thawing what you’ll immediately use.
  • Pre-freeze on a baking sheet before bagging for individual portions.
  • Add a piece of parchment to absorb moisture.
  • Store frozen cheese towards the back of the freezer.
  • Use within 1-2 months after thawing for best flavor.


Checking for signs of spoilage is the best way to determine if your Parmesan cheese is still fresh and safe to eat. With proper refrigeration, an unopened block of Parmesan will stay good for at least 8-10 months past the printed “best by” date. Once opened, tight wrapping and minimal exposure to air help prevent drying out or mold growth. Discard Parmesan at the first signs of mold, unpleasant odors, changes in texture, or odd colors. Freezing can also prolong the shelf life of Parmesan. Knowing what to look for and how to store Parmesan correctly helps prevent wasting this delicious cheese.

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