Can you leave grated Parmesan cheese out of fridge?

Quick Answer

Grated Parmesan cheese can be safely left out of the refrigerator for a short period of time. However, for best quality and food safety, it is recommended to refrigerate grated Parmesan after opening. An unopened wedge or block of Parmesan can be kept at room temperature for up to 2 months.

Can Grated Parmesan Cheese Be Left Out at Room Temperature?

Yes, grated Parmesan can be left out at room temperature for a short period of time without spoiling. According to the University of Wisconsin-Madison Food Safety and Health Department, grated Parmesan will stay fresh for about 2 hours if left out on the counter.[1]

However, it is best to refrigerate grated Parmesan cheese after opening to maximize freshness and prevent potential bacteria growth. The low moisture content and granular texture of grated Parmesan make it less perishable than many other dairy products. But leaving it out too long can still allow mold or harmful bacteria to grow.

How Long Does Grated Parmesan Last at Room Temperature?

Here are some general guidelines for how long grated Parmesan will last unrefrigerated:

– 2 hours: Safe to eat but will start to lose quality[1]
– 4-6 hours: Increased risk of spoilage
– 8+ hours: Discard for food safety

On a very hot day (over 90°F), grated Parmesan should not sit out for more than 1 hour.[2] The warmer temperature speeds up bacterial growth.

Does Refrigeration Prolong Shelf Life?

Yes, refrigerating grated Parmesan cheese helps extend its shelf life significantly by slowing bacteria growth. According to Eat By Date, grated Parmesan will last about:[3]

– Refrigerator: 2-3 months
– Freezer: 6-8 months

Properly stored in the fridge, grated Parmesan can maintain good quality and safety for months after opening. Make sure to keep it in an airtight container.

Can You Leave Parmesan Cheese Wedge Out?

An unopened wedge or block of Parmesan cheese does not need to be refrigerated. It is very shelf stable and can be kept at room temperature for extended periods.

According to the Australia New Zealand Food Standards Code, Parmesan cheese can be stored unrefrigerated for up to 2 months.[4] After opening, it is best kept in the fridge but can stay out 1-2 weeks before quality loss occurs.

The typical shelf life for Parmesan chunks or wedges is:

– Unopened at room temperature: 2 months
– Opened, refrigerated: 3-4 months
– Opened, room temperature: 1-2 weeks

Why Can Parmesan Wedges Stay Unrefrigerated?

Parmesan wheels and wedges are very low moisture cheeses, typically containing 32% water or less.[5] Low moisture environments make it difficult for bacteria to grow.

The aged, granular texture also contributes to Parmesan’s shelf stability. Aged hard cheeses like Parmesan have lower pH levels and active cultures that further prevent spoilage.[6]

Finally, the large size and shape of Parmesan wedges means there is less surface area exposed to air. This slows down oxidation reactions that can cause rancidity.

Does Lightly Grated Parmesan Stay Good at Room Temp?

Lightly grated Parmesan that still maintains a good amount of chunky pieces can have slightly better room temperature stability than finely grated cheese.

The University of Wisconsin states that lightly grated Parmesan will last 3-4 hours at room temperature, compared to 2 hours for finely grated.[1]

Larger grated pieces have less surface area exposed. This helps retain moisture and slows down microbial growth and enzymatic breakdown of fats.

However, it is still advisable to refrigerate any grated Parmesan within 4 hours of opening. Leaving large gratings out longer than 4-6 hours can pose food safety risks.

Tips for Storing Grated Parmesan Cheese

Here are some tips for maximizing the shelf life and safety of your grated Parmesan cheese:

– Refrigerate grated Parmesan in an airtight container after opening. Use within 2-3 months for best flavor.

– If leaving grated cheese out for a recipe, discard leftovers after 2 hours at room temperature.

– For longer storage, freeze grated Parmesan in a freezer bag or airtight container up to 8 months.

– When taking Parmesan out of the fridge, allow it to come to room temperature before serving for better flavor.

– Keep Parmesan wedges wrapped in parchment paper or cheese paper until ready to use. After opening, wrap tightly in plastic wrap before refrigerating.

– Look for mold growth or strange odors before eating grated Parmesan. Discard if anything looks or smells off.

– Avoid introducing extra moisture into the Parmesan container, as this creates an environment for bacteria to grow.

The Bottom Line

Grated Parmesan cheese is best stored in the refrigerator after opening, where it will keep for 2-3 months. At room temperature, finely grated Parmesan will stay fresh for about 2 hours before quality loss occurs. Lightly grated cheese may last 3-4 hours.

Hard Parmesan wedges and blocks keep much longer than grated cheese. An unopened wedge can be kept at room temperature for up to 2 months. Once cut into, Parmesan chunks should be refrigerated but can sit out about 1-2 weeks before spoiling.

Storing grated or shredded Parmesan cheese in the refrigerator will maximize its shelf life and freshness. But even when kept at room temperature, the low moisture and granular texture allow it to keep longer than many dairy products.

Frequently Asked Questions

Can you get sick from Parmesan cheese left out overnight?

Most likely you will not get sick from Parmesan left out overnight, as the risk of harmful bacteria growth is low. However, for best safety and quality, do not leave grated Parmesan out more than 8 hours. Discard any cheese that smells odd or has mold.

How long can shredded Parmesan be left out?

Finely shredded Parmesan should not be left out more than 2 hours at room temperature. Coarsely shredded cheese may last 3-4 hours. For optimal freshness and food safety, refrigerate shredded Parmesan in an airtight container.

Why does my Parmesan cheese get moldy so fast?

Grated Parmesan left out too long can develop mold. To prevent mold, make sure to refrigerate grated Parmesan in an airtight container after opening. Wipe down the container to remove moisture before storing. Use shredded Parmesan within 2-3 months for best quality.

Can you put Parmesan cheese back in the fridge after leaving out?

It is best to avoid refrigerating Parmesan cheese after it has been left out at room temperature for more than 2 hours. The temperature fluctuation can increase moisture and risk of bacterial growth. Parmesan left out more than 4 hours should be discarded.

Does Parmesan cheese need to be refrigerated once opened?

Yes, it is recommended to refrigerate Parmesan once opened, whether grated or in wedges. Tightly wrap or store cheeses in an airtight container. Properly stored, grated Parmesan will last 2-3 months in the fridge, and Parmesan wedges will last 3-4 months refrigerated.


Grated Parmesan cheese can be left out at room temperature for a short period before quality loss occurs. But refrigeration is the best way to maximize shelf life after opening. Parmesan wedges and blocks are quite shelf stable, lasting months unrefrigerated when still sealed in the original packaging. Once opened, Parmesan chunks can still keep 1-2 weeks at room temperature. Following proper storage methods allows you to keep this flavorful and versatile cheese fresh for months.

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