Question: why does milk go rotten when u dont keep it in a fridge

Gonzalo Delgado-Pando answered on 7 Nov 2017:

The milk goes rotten even if you keep it inside the fridge it all depends on the time. The higher the temperature the shorter the time for the milk to go rotten. Most all the foods will get rotten if you leave them in contact with air enough time. This happens because in the air there are some realy tiny bugs that feed from the food (in this case milk) and when they grow a lot, the food gets rotten. There are also some bugs in every food that will keep growing if left for enough time, again if they grow a lot they will rot the food. Most of this little tiny bugs grow better at mild temperatures, let’s say summer temperatures and that is why the food gets rotten faster when kept outside the fridge and even faster if it is in a hot room.
But don’t worry about this little bugs, they are harmless up to certain amount. If you check the (the bottle of milk you will see a date (normally on the cap), the milk will be good for drinking up to that date if kept closed in the fridge. If it is open in the same pacakge it will say how many days you can keep it with no problem. The same with any other packaged food.