(4) Ripening is a process in fruits that causes them to become more palatable. In general, a fruit becomes sweeter, less green, and softer as it ripens. Even though the acidity of fruit increases as it ripens, the higher acidity level does not make the fruit seem tarter. Ethylene, It is also the gas that is released by ripening fruit (this is why you can ripen unripe fruits by putting them in a paper bag along with one piece of ripe fruit). The chemical formula for Ethylene is: C2H4 . Like any hydrocarbon, it is a flammable gas.