A plantain is ripe when the peel is completely black and wrinkly and yields easily when mild pressure is applied to it. It takes three to four weeks for a plantain to ripen completely.
Plantains can be ripened by placing them in a warm place with good ventilation. If the weather is hot or humid, they should not be stacked together because this promotes mold. Plantains have less moisture content than bananas and take longer to ripen. Bananas have an average moisture content of 83 percent, but plantains have only 65 percent. The moisture content affects the conversion of starches to sugars. The higher the moisture content, the faster the conversion.