As bananas ripen and develop black spots, their flavor becomes much sweeter, the peel thinner, and the pulp softer. It can take more than a week to reach this point. In a banana emergency, an alternative method of ripening is to freeze bananas in the peel overnight. They can be defrosted in less than 30 minutes in a room-temperature water bath, then slit lengthwise and the pulp removed. Ripening bananas naturally, however, produces a sweeter flavor. Any extra banana pulp can be frozen for several months.