I have an unopened vacuum packed ball of Mozzarella. How long can I keep it refrigerated before it goes bad? I'm getting mixed answers.
My best advice would be to adhere to the manufacturer's guidelines, and push them at your own risk. Cheese doesn't usually go bad "all at once" but you can definitely get sick from eating spoiled or moldy cheeses.
The most common notice I have been able to find for various brands available for ordering online reads something like this:
Freshness is assured in unopened package until the date stamped on the front of the package. Use within 3-5 days after opening or freeze up to 2 months.
Though, I have a bag of mozzarella in my freezer right now, which I purchased at the local supermarket, for which the manufacturer's note states it can be frozen up to 6 months.
Generally, the expected shelf-life of Mozzarella cheese depends on many factors, including:
How the cheese was produced. Some methods spoil faster than others. Typically low-mosture cheeses last much longer (some claiming 6 months or more).
The packaging. Some mozzarella (like other cheeses) comes in specially designed packaging that claims to prolong the life of the cheese.
The temperature of storage. Frozen cheese lasts significantly longer, around 6 times as long.
If you plan to store it a long time, refrigerate it more strongly - that is, freeze it. Not so good for the texture of fresh cheese, but does not affect the texture of melted cheese a bit.
Otherwise, there really is no hard and fast guideline - "vacuum packed cheese" is relatively well sanitized, but it's not sterile. Storage and handling conditions and the precise temperature of your fridge, and every storage condition back to the factory will have some impact.
Being cheese, if it looks good, it probably is good. If it looks bad, throw it out.
Based on various times when "string cheese" has been inexplicably less expensive than a pound package of mozzarella (despite much greater packaging expense) I'd give it a month or two easy if the fridge is cold and the package unopened.
Generally, it is safer to freeze cheeses for a long storage. However, anything two weeks or less is generally an okay period of time to keep cheese refrigerated, as long as it isn't exposed to air. This is how long it takes for a noticeable amount of bacteria/fungi to grow on moist foodstuffs.
Refrigeration and vacuum sealing allow a cheese to be not spoiled for a very long time. Add to that the fact that most cheese are very low in carbs.
The only thing I'd worry about is the degradation of the product -- it doesn't matter how long there is no bacteria if the product starts becoming chewy or brittle or separated. I don't think this will apply too much to mozzarella.
So with respect to your example, I'd go with several years as my answer (unless you see air being generated in the package..). But make sure to check on the texture during your experiment to determine if the proteins are starting to break down. This can be a simple as a taste test, since again, I'm not worried about the bacterial part.
I'm not a chef, and I'm not a food scientist. Since the interweb answers are vague and generic, I get the impression that general rules apply, and that the consequences are not that bad.