Export bananas are picked green, and ripen in special rooms upon arrival in the destination country. These rooms are air-tight and filled with ethylene gas to induce ripening. The vivid yellow color normally associated with supermarket bananas is in fact a side effect of the artificial ripening process. Flavor and texture are also affected by ripening temperature. Bananas are refrigerated to between 13.5 and 15 °C (56 and 59 °F) during transport. At lower temperatures, ripening permanently stalls, and turns the bananas gray as cell walls break down. The skin of ripe bananas quickly blackens in the 4 °C (39 °F) environment of a domestic refrigerator, although the fruit inside remains unaffected.
"Tree-ripened" Cavendish bananas have a greenish-yellow appearance which changes to a brownish-yellow as they ripen further. Although both flavor and texture of tree-ripened bananas is generally regarded as superior to any type of green-picked fruit, this reduces shelf life to only 7–10 days.
Bananas can be ordered by the retailer "ungassed", and may show up at the supermarket fully green. "Guineo Verde", or green bananas that have not been gassed will never fully ripen before becoming rotten. Instead of fresh eating, these bananas are best suited to cooking, as seen in Mexican culinary dishes.
A 2008 study reported that ripe bananas fluoresce when exposed to ultraviolet light. This property is attributed to the degradation of chlorophyll leading to the accumulation of a fluorescent product in the skin of the fruit. The chlorophyll breakdown product is stabilized by a propionate ester group. Banana-plant leaves also fluoresce in the same way. Green bananas do not fluoresce. The study suggested that this allows animals which can see light in the ultraviolet spectrum (tetrachromats and pentachromats) to more easily detect ripened bananas.