Pork has gone bad when the color changes from pink to brown (or gray) and starts to have a sour smell. When this happens, safely discard the pork.
If pork has been in the freezer for too long, it develops freezer burn that appears as dull white patches on the outside. These white patches develop inside the meat as well. Properly storing the pork extends the expiration date. For instance, when pork is refrigerated, it has a shelf life of 1 to 2 days after the sell-by date. When it is kept in the freezer, the shelf life is extended to 6 to 8 months beyond the sell-by date. It is best to practice food safety and eat the pork in the proper time frame.