When properly stored, opened pineapple juice can last for one week. It's important to look for signs of spoilage prior to drinking it or using it in a recipe, however, or a seemingly healthy product can be anything but good for you. While pineapple juice is acidic, that doesn't afford protection from harmful bacteria.
Opened pineapple juice needs some simple checks: Is today's date prior to the expiration date? Has it been opened less than one week? Has it been continuously refrigerated and covered? Does it lack mold? Does it smell fresh? Positive answers to these questions keep you safe and give you juice with optimal nutrition and taste.
Canned pineapple juice must be checked for dents or bulges prior to opening because a pinhole opening in the crease of a dent can allow harmful bacteria to enter, and a bulge can mean bacteria has produced gas byproducts inside the can. Once opened, pineapple juice should be promptly removed from a metal can and stored in a covered glass or food-safe plastic container in a refrigerator 40 degrees Fahrenheit or lower. Juice packaged by a grocery store, juice bar or restaurant could be unpasteurized and should be refrigerated within an hour and consumed within a day. Unpasteurized juice is labeled as such. It can contain harmful bacteria hazardous to those with weakened or insufficient immune systems, including children and the elderly. Those at risk should only consume pineapple juice that states "pasteurized" on the label.