Bananas do not bruise as they age, unless they are mishandled.
Liken the black spots on bananas to the liver spots on mature adults…they appear with age, even if they go untouched. The hormone ethylene, a ripening agent found in the skin of the banana, transforms a green banana into the appealing yellow fruit we purchase at the market.
The ripening agent in the skin of the banana makes a green banana into the yummy yellow fruit we get at the store and it continues to ripen which gives the banana a "bruised" appearance, and eventually turns the banana black! :DD
They get old. It's like how apples get soggy when they are old.
that happens to them when you freeze them
They get old