Our long yellow friends are full of surprises … It takes a couple of weeks for a banana in a fruit bowl to turn black. But if you put one in the fridge overnight, it’ll be black by the morning. So why does doing something that normally preserves food speed up the decay of this kind of fruit? Bananas are a tropical fruit and they can’t cope with the cold temperature of the fridge. The cold damages the cells in the same way that age does as the fruit ripens. Both cold and age encourage an enzyme called polyphenyl oxidase to ‘polymerise’ (in other words, link together) compounds called phenols in the banana skin. When they’ve linked together, they become ‘polyphenols’ . And these are similar to melanin, the pigment responsible for the colour in our skin. So polyphenols make humans get a suntan – and bananas get a ‘coldtan’! Top Tip: Ethylene gas is released as the banana’s cells are damaged – either by ripening or by cruelly placing it in the fridge. This ethylene not only causes the banana to ripen, but also affects any other fruit nearby. So if your peaches, nectarines or any other soft fruit are just that bit too hard, pop a banana in the fruit bowl with them to hurry their ripening along. Go back