I like to save my Parmigiano-Reggiano rinds for tossing in homemade soups. I always go through the cheese much faster than I can use the rinds, though, so I often have a bunch of them sitting around in my fridge for a long time.

I have two questions: How can you tell if a parmesan rind has gone bad? I'd hate to ruin a good soup that way, but I really don't know how to tell unless it smells funky or has excessive mold--and they usually have white spots anyway. Also, what about freezing them? I know it's not usually the best idea to freeze cheese, but I'm wondering if it would be okay with a hard aged cheese like this.