It’s not always obvious when food has gone bad, but blue mold and a funky smell are usually clear signs that something belongs in the trash. That is, unless you’re dealing with blue cheese, a product that by design includes blue-green speckles of mold. So how are you to tell the difference between the tasty kind of old, moldy cheese and the kind that will make you sick?

Before cleaning out your cheese drawer, you should first familiarize with what a desirable hunk of blue cheese looks and smells like. Carie Wagner, one of Wisconsin’s elite master cheesemakers, told The Takeout that good blue cheese should have greenish-blue veins and a body that’s cream to white in color. Blue cheese is also supposed to be pungent—if the smell that first hits you when you peel back the plastic is comparable to ammonia, that’s not a bad thing.

But there are some living things you never want to see growing on your cheese, even if mold is the main selling point. Fuzzy gray or black patches of mold or shiny pink or yellow spots of yeast are indications that your blue cheese is past the point of no return. Cheese that is slimy or feels tough and dry has also likely spoiled.

As with most foods, the easiest way to tell if blue cheese is safe to eat is to use your senses and basic judgment. Does that last piece in the back of fridge look a little discolored? Does it smell funky in a way that tickles your gag reflex, not your taste buds? You probably shouldn’t eat it.

And if all blue cheese smells equally rotten to you, perhaps you should stick to snacks that don’t resemble science experiments quite so closely. If you do decide to pair some blue cheese with a glass of wine, make sure the vino you intend to sip also hasn’t spoiled.

[h/t The Takeout]

A version of this story originally ran in 2018; it has been updated for 2023.

This article was originally published on www.mentalfloss.com as How to Tell If Your Blue Cheese Has Gone Bad.