One of the worst cases of food poisoning I've ever had came from bad mozzarella.
As the other say, open it. Any whiff of 'off' odor, or any odor for that matter, out it goes. I generally approach expiry dates with a grain of salt, but after that bout of agony I stick with 'best by' dates with mozzarella. Or any dairy product.
Perhaps I would try it as Dodgyken says- but as I have visitors from AZ and CA arriving at the week-end- don't want to risk it- So, out it goes- I'll put it in the back field tonight for the foxes, they won't mind.
When we've had bad mozarella it makes the pack inflate.
I've had it a couple of times in an opened dish - the acid gives it a slightly "fizzy" flavour or sensation that's obvious. But with weekend constraints I wouldn't chance it either.
Well if it's a sealed pack it would still be in its brine, so no way could it have gone "off". Cheese is already milk gone "off", so unless it's exposed to the air and the mould spores therein it will be absolutely fine.
It won't taste as good, most likely, assuming you're talking about real mozzarella and not the plastic stuff you buy in blocks, but I think the risk of it being bad is about 0%.
Edit: for sealed prepacked pasteurised cheeses, I wouldn't normally start to be concerned as long as it looks and smells OK, no matter how old it is. Even if it is past its best it's more just a question of flavour than anything else.
If it looks and smells ok, eat it. You'll be fine. Might not be as tasty as it started out, especially if it's well past the expiry date, but it won't do you any harm.
If it looks mouldy and smells fine, you can cut out the mould (if the piece is big enough to warrant it). If it smells off, bin it.
If you don't trust your eyes or nose to examine it, bin it.
One farmer down the road keeps lots of buffalos and makes great mozzarella- sold under the name of Bufflone. But the one past the date is Galbani- in sealed pouch with 3 separate pouches inside.
Oh, I know the ones you mean. I found one of those in the back of my fridge once that was nearly a year out of date (don't ask). I opened it, still looked and smelled like cheese, just somehow... cheesier. So I ate it. It tasted like a nice Provolone, but with a creamier mozzarella-y texture. Very nice indeed. If we could spare the fridge space (and if Mr. MathNut weren't so horrified at the thought ) I'd be tempted to make a habit of that.
ahahah ok you've won- I'll keep it until both lots of visitors have gone (they are all lovely so won't try it on them) and then I will open the pack and have a good sniff and decide. Could do with losing a few pounds, so if it all goes wrong- it will help me on the way.
Any ideas on what to do with it more interesting than just slicing and eating with tomatoes and basil. Please?
Hope you all get to taste our local Val-de-Travers Bufflone one day- we love having the herds of buffalos round here