How long will opened tomato juice stay safe to eat stored in fridge?

This food will keep for about 3 to 4 days in the refrigerator. Place the food in an air tight container or plastic pitcher for the best results. Never store vegetable juices in the can in the refrigerator.

I store my juice in the fridge in a plastic bottle and I have noticed after a few days pressure starts to develop in the bottle. I can't find anything about this, but I would say it happens when the juice is starting to go bad.