Unopened refrigerated orange juice has an average shelf life of one to two weeks. Once opened, it lasts between five and seven days. You will typically know that your orange juice is sour even before you look at its stamped expiration date, since it may start to ferment or form mold. In either case, it's time to dump it. If you know what to look for, you may still be able to use orange juice after the expiration date has passed.
Feel the orange juice container for puffiness. If the container seems to bulge at all or if it is very firm to the touch, the cause may be fermentation. Fermentation is the result of bacteria that has begun to break down the juice into alcohol and sugars.
Open the container and smell the contents. A sour or sharp smell can indicate fermentation. If you smell nothing unusual, do not drink the juice until you investigate further. Look inside the container for mold, which may appear as light or dark spots on the walls of the container or in the juice itself. Discard the juice if you detect any signs of mold.
Pour some juice into a clear glass and inspect it for signs of mold. A pure orange color indicates that you can safely drink the juice.