Like many other fruits, bananas give off ethylene gas, which speeds up ripening. Keep bananas away from other fruits and ensure that they have good air flow by breaking up the bunch. If the stems came covered in plastic wrap, do not remove the plastic until ready to eat as this will slow the release of ethylene gas.
To keep bananas from browning quickly, break up the bunch and separate. Don’t store bananas with apples, which speed up ripening.