There are a few easy ways to tell if your Brie is bad. It should not be ammonia-smelling or have an off smell. A white powdery exterior indicates that your cheese is not bad. If it has a mouldy or funky smell, it should be discarded. You should also taste it to determine whether it is still edible.
If it has a strong, sour or metallic flavour, discard it. If you’re unsure of how to tell if Brie is going bad, try a slice to see how long it has been in the refrigerator. It should still be edible.