How Long is Grated Parmesan Cheese Good For After Opening?(Answered!)

For health and safety reasons, you really need to know how long is grated parmesan cheese good for after opening.

After all, you don’t want any unpleasant side effects from eating parmesan that has gone off.

And, of course, the taste may be affected too.

Does parmesan last longer if it’s not grated?

How can you tell if the parmesan has gone bad?

Does it last longer because it’s hard cheese?

Let’s find out, shall we? 

Once opened, parmesan has a limited life span before it becomes unfit for consumption. A typical period would be approximately one week, assuming it is refrigerated in an airtight container. If the block of parmesan is kept whole once opened, not grated, it could last as long as two months. As the parmesan goes off, it will change color and develop mold. As parmesan is a hard cheese, it will last longer than softer cheeses. This is because it lacks moisture. And it is the moisture that attracts bacteria, causing the cheese to go bad. 

Once Opened, How Long is Shredded Parmesan Cheese Good For?

Like most of us, I bet you buy larger packs of shredded parmesan, more than enough for one meal.

So, once you have opened it, how long is the parmesan good for?

Well, first of all, it does need to be refrigerated and preferably stored in an airtight container.

If that’s the case, you are looking at a period of about a week.

However, if you buy the parmesan as a whole block and only grate what you need, it will last much longer. 

In fact, it could still be edible for up to two months.

This could be a more cost-effective way to buy your parmesan.

When the cheese is grated, it exposes more of its surface area.

So, as you can imagine, that gives more opportunities to attract bacteria.

Parmesan actually lasts a lot longer than other cheeses.

This is because it is classed as hard cheese; it has a low moisture content.

Moisture is known to be a breeding ground for bacteria, causing food to go moldy.

So, a softer cheese that contains more moisture is likely to go off quicker than parmesan.

How Do You Know if Grated Parmesan Has Gone Off?

Thankfully, there are several visual clues to indicate that your parmesan has gone bad.

The most obvious will be patches of blue or green mold.

But the overall color of the parmesan may also change. 

Fresh parmesan is very pale in color, almost white or a very light yellow. 

Once the cheese starts to deteriorate, it will become darker and more orange-colored.

The smell of parmesan is quite distinctive, and some find it unpleasant, as though it has already gone off!

So, relying on the odor of the cheese to indicate if it is still fit to eat may not be reliable.

You can also check the texture of the parmesan; it should flow freely and feel dry to the touch.

If it’s at all wet or feels spongy, it should not be eaten.

One thing to remember is that you shouldn’t just try and pick out any pieces that are moldy.

The mold spores are likely to have spread through the whole packet, even if you can’t see them.

So, unfortunately, you need to throw it all away to be on the safe side. 

The exception to this is if it’s a whole block of parmesan.

In that case, you can just cut the moldy section off.

Does Parmesan Go Bad?

Final Thoughts

Once grated parmesan is opened, it is unlikely to last more than a week. 

This is because there is more surface area exposed that could attract bacteria.

It should always be refrigerated in an airtight container.

However, a whole block of parmesan could last for two months.

You can recognize when parmesan has gone bad as it will either change color or have visible patches of blue or green mold.

Please don’t take any risks with your health.

If you have any doubts about your parmesan cheese, you need to throw it away.

If you are concerned about other cheeses, read my article on how to know if halloumi is safe to eat.

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