How do you know if grated Parmesan cheese is bad?

Parmesan cheese is a hard Italian cheese that is widely used for grating and sprinkling on top of pasta dishes, salads, soups, and more. It has a distinct nutty and salty flavor that enhances many recipes. However, there are several ways you can tell if your grated Parmesan cheese has gone bad and is no longer safe to eat.

Check the expiration date

The first and easiest way to check if your grated Parmesan is still good is to look at the expiration date printed on the packaging. Parmesan is typically safe to eat 1-2 months past the printed expiration date, as long as it has been stored properly in the refrigerator. If your cheese is more than a few months past the date, it’s best to throw it out.

Look for mold

Mold growing on cheese is a sure sign it has spoiled. Carefully inspect the Parmesan wedge before grating it, looking for any fuzzy white, blue, green, or black mold. Small dots of blue or green mold can embed deep in the hard cheese and may only show up once grated. If you see any mold at all, play it safe and discard the cheese.

Smell the cheese

Fresh Parmesan should have a distinct salty, nutty, and umami aroma. A sour, unpleasant, or ammonia-like smell is a red flag that the cheese has gone bad. The odor will be more noticeable once grated. If it smells off, err on the side of caution and toss it.

Check the texture

Good Parmesan should be dry and brittle with a hard texture. Cheese that has a soft, mushy, or rubbery texture has typically gone bad. There may be some lumps in grated cheese that have absorbed moisture. Discard any pieces that are gummy or mushy.

Look for odd flavors

Taste a small amount of freshly grated Parmesan to check for any “off” flavors. Rancid, bitter, or sour notes indicate spoilage. The cheese should taste like the salty, savory Parmesan you are familiar with. If not, it is not worth taking a chance and you should throw it away.

Check for dryness

Properly stored Parmesan often becomes dry and grainy but is still safe to eat. Inspect the grated cheese and rub a pinch between your fingers. It should not feel overly dry and coarse. Intense dryness can be a warning sign it is past its prime.

Observe the color

Parmesan is typically pale yellow in color. Grayish, brown, or orange discoloration suggests the cheese has aged too long. While small brown specks are normal, excessive dark spots indicate the cheese has oxidized and should be discarded.

Consider how long it’s been open

Once opened, grated Parmesan will only stay fresh for a short time in the fridge. An opened package or container will stay good for about 1 month. Unopened, it will last 6-8 months past the printed date. If your cheese has been open for a while, it’s safest to throw it away.

Has it been improperly stored?

How you store Parmesan can directly affect its shelf life. Keeping it tightly wrapped, in an airtight container, and in the coldest part of the refrigerator preserves freshness. If it hasn’t been properly covered and refrigerated, it will go bad faster. Heat, moisture and air cause it to spoil quickly.


Here are some key signs that your grated Parmesan cheese has gone bad and needs to be discarded:

  • Mold growing on the cheese
  • Unpleasant sour or ammonia smell
  • Soft, mushy, rubbery or gummy texture
  • Odd, bitter or rancid taste
  • Excessive dryness and coarse gritty texture
  • Grayish, brown or orange discoloration
  • Past the expiration date by more than 2 months
  • Opened for more than 1 month
  • Stored improperly at room temperature

Trust your senses – if the cheese smells, tastes or looks off in any way, err on the side of caution and throw it out. With grated Parmesan, it’s better to be safe than sorry if there’s any doubt about its freshness. Following proper storage methods, checking expiration dates, and being aware of signs of spoilage will ensure your cheese stays fresh and enjoyable.

Frequently Asked Questions

How can you tell if pre-grated Parmesan cheese is bad?

Check pre-grated Parmesan for mold, clumping, odd or sour smell, bitter taste, and grayish or orange discoloration. Also note if it is past the expiration date or has been open for more than 1 month.

Can old Parmesan cheese make you sick?

Yes, eating cheese with mold or that has spoiled can make you sick. Consuming bad Parmesan can cause food poisoning symptoms like nausea, vomiting, stomach cramps, and diarrhea. In severe cases, it can even cause a life-threatening infection.

What happens if you eat Parmesan cheese with mold?

Eating Parmesan with mold can cause food poisoning. Mold can contain mycotoxins that cause illness. Symptoms include nausea, vomiting, abdominal cramps, diarrhea, and fever. Those with compromised immune systems are at higher risk of severe infection.

Can you get food poisoning from Parmesan cheese?

Yes, Parmesan can cause food poisoning if it is contaminated with dangerous bacteria like Salmonella, Listeria, Staphylococcus aureus, or E. coli. Symptoms include nausea, vomiting, diarrhea, fever, chills, and body aches. Seek medical treatment if symptoms are severe.

How long is grated Parmesan cheese good for after opening?

In the refrigerator, an opened package of grated Parmesan will stay fresh for about 1 month past its printed expiration date. Tightly rewrap or transfer to an airtight container to help extend its shelf life after opening.

Can you eat Parmesan cheese that is hard?

Hard texture alone doesn’t necessarily mean Parmesan has gone bad. Properly stored, it often becomes dry and grainy but is still safe to eat. However, if it is overly hard and dry or has other signs of spoilage like mold, odor, or funny taste, it should be discarded.

Why did my Parmesan cheese turn yellow?

A yellow discoloration in Parmesan is typically a sign of oxidation. This happens from exposure to air and light. While small yellow spots are harmless, excessive yellowing means the cheese has aged too long and should be thrown out.

Is it OK to eat Parmesan cheese with spots?

Small brown or white spots in Parmesan are fine to eat and are caused by the presence of calcium lactate crystals. However, blue, green, black, or fuzzy mold spots indicate spoilage and the cheese should be discarded. When in doubt, play it safe and toss it.

Can Parmesan cheese be frozen to extend shelf life?

Parmesan can be frozen in an airtight container or bag for up to 6 months. This stops mold growth and bacterial activity that causes spoilage. Thaw in the refrigerator before using and use within a week for best flavor.

Tips for Storing Parmesan Cheese

Here are some tips to help keep your Parmesan cheese fresh for longer:

  • Keep Parmesan tightly wrapped in plastic wrap or in an airtight container.
  • Store in coldest part of the refrigerator, not the door.
  • If grated, use within 1 month of opening.
  • Wipe exterior of cheese to remove moisture and crumbs.
  • Separate a wedge from the rind to prevent mold.
  • Stack cheese on a clean plate vs. directly on refrigerator shelf.
  • Freeze for longer storage up to 6 months.

Signs of Spoilage in Other Cheeses

Here are signs of spoilage to look for in other popular cheese varieties:

Cheese Type Signs of Spoilage
Blue cheese Brown, yellow, or pink mold (safe mold is blue or green), ammonia smell, slimy texture
Brie Mold other than white, ammonia odor, signs of bubbles or fuzz
Cheddar Mold, bitter flavor, soft or crumbly texture, gas pockets, dry and flaky
Cottage Cheese Sour smell, excess whey, lumpy curds, pink, yellow or blue discoloration
Cream cheese Mold, sour taste, runny texture, gray or orange discoloration
Feta Dry, crumbly, chalky texture, rancid smell, brown liquid in package
Goat cheese Ammonia smell, excessive mold, dried out and overly hard
Gruyère Mold, cracks or crystals in texture, vinegar smell or taste
Mozzarella Sour smell, orange oil on surface, excessive mold or dry spots
Ricotta Whey separation, yellow or pink tinge, sticky texture, putrid smell

The key for any variety is to watch for mold, foul odors, changes in color or texture, and to discard if you have any doubts about safety or freshness. With soft cheeses, it’s best to stick to the expiration date and use within a week of opening. With hard cheeses, you may have a little longer but it’s always better to be safe than sorry when determining if your cheese is over the hill.

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