Bananas that require further ripening should be left at room temperature, but away from heat or direct sun. To speed ripening, place them in a loosely closed paper bag. Putting an apple in the bag will further speed the process. Once ripened to your liking, bananas can be held at room temperature for a day or two. Then, you can store them in the refrigerator to slow down ripening; although the skins will turn dark, the fruits will remain perfectly edible. Never refrigerate unripe bananas: The exposure to cold interrupts their ripening cycle, and it will not resume even if the fruits are returned to room temperature.