Both sweet and tart, pineapple's distinctive flavor lends a tropical touch to any dish. Pineapples stop ripening immediately upon removal from the tree, so technically, there's no way to change the texture or quality of the interior of the fruit once it's picked. The only thing you can do is change its color on the outside. Fruits like apples, nectarines and pears release ethylene gas, which changes the color of the pineapple's exterior from green to yellow but does not ripen the inside.
Look for pineapples with bright green leaves, yellow coloring to the rind and a sweet odor indicating ripeness. Avoid fruit with brown leaves.
Place a whole pineapple into a paper bag with a whole apple.
Fold the top of the bag over and leave at room temperature for one day.
Remove the pineapple, cut and use immediately or refrigerate for up to one week.