As I understand it, there are no preservatives used in bananas.
The difference is that presumably the organic ones are raised without insecticides, and allowed to ripen naturally.
Non organic bananas are put in a chamber with natural gas that provokes them to ripen.
On all the banana plantations I have seen, the bananas are placed in large plastic bags after the flowers have been plucked off the end of each banana, and the bags only come off after the harvest. In most of the US, all bananas are of the Cavendish species. Cavendish bananas ripen very slowly. All bananas you see in stores are harvested while green. Many other varieties are available in Miami, and all of them ripen much faster. If they ripen on the plant, they are sweeter. And you have dozens of them ripening all at the same time.