What causes brown spots on bananas?

The answer

They develop as the peel ages and enzymes and oxygen act on compounds in it. Spotty bananas are usually very ripe, soft and sweet, and they are ideal for banana bread, pancakes and smoothies because the starch has turned to sugar. Judge a banana by smell, texture and any sign of mold rather than by spots alone. A large bruised patch or mushy dark area across the whole peel deserves a closer look for spoilage.