Air is the enemy for bananas to turn dark. Also, exposure to metals (like your knife to cut them) can accelerate the darkening process. The best tips to minimize the bananas from turning dark are: - Don't slice bananas until you are ready to use them. - Use ripe (not over-ripe) bananas. - Slice bananas with a plastic knife. - Keep plastic wrap or banana peel over bananas until they are used. - Store banana pudding in an airtight container. The pudding and meringue seal air away from the bananas, so be sure your topping covers the whole pudding to keep air out and bananas fresh!