Green bananas can be eaten, although they are harder to peel, have a bitter, starchy flavor and the texture is firmer than a yellow banana. A green banana is simply an unripe banana that turns yellow and then brown as the fruit matures.
As the fruit ripens, the banana becomes sweeter and softer as the cells break down, and the sugars concentrate within the fruit's flesh. Different consistencies of banana are used for different recipes. While the softer yellow or brown bananas are frequently used for banana bread and pudding, green bananas are often fried or processed and turned into a gluten-free flour. Bananas are a naturally radioactive fruit, containing the isotope potassium, though in small enough amounts as to be harmless.