Ethylene is a hormone gas that stimulates fruits to ripen. Most fruits and vegetables generate ethylene gas while they ripen. Many growers pick the fruits and veggies before they ripen so they can handle them easier without causing damage. Right before they are delivered to market they treat them with a synthetic ethylene. Have you heard the expression,"One bad apple can spoil the whole bunch?" Sometimes fruit we buy at the store isn't ripe enough yet. If you want to ripen a fruit faster (so it tastes sweeter) why is it suggested to put the fruit in a brown bag?