Cucumbers should be stored separately from bananas because bananas release ethylene gas, which accelerates the ripening and spoilage of cucumbers, causing them to become yellow, soft, and mushy.
Bananas, like many fruits, produce ethylene gas as they ripen. Ethylene is a natural plant hormone that acts as a ripening agent. While this is beneficial for some fruits, it can be detrimental to others, especially ethylene-sensitive vegetables like cucumbers. When cucumbers are exposed to ethylene gas, their ripening process is sped up significantly. This leads to a breakdown of chlorophyll, causing the cucumber's green color to fade and turn yellow. The texture also changes, becoming soft and eventually mushy as the cell walls degrade. Storing cucumbers away from ethylene-producing fruits like bananas helps to prolong their freshness and maintain their desired texture and flavor. Other fruits that produce high levels of ethylene include apples, avocados, melons, and tomatoes.
To maximize the shelf life of your cucumbers, store them in the refrigerator crisper drawer, ideally wrapped in a slightly damp paper towel inside a plastic bag. This helps maintain humidity and prevents them from drying out, further extending their freshness.