Freezing sweet potatoes can greatly extend their shelf life, and the key to maintaining their vibrant orange color lies in adding lemon juice. The ascorbic acid in lemon juice inhibits a chemical reaction known as enzymatic browning, which causes sweet potatoes to turn brown and lose flavor and nutrients. It is recommended to peel and cook the sweet potatoes before freezing them, and freezing them separately on a parchment paper-lined baking sheet will prevent them from sticking together. When ready to use, frozen sweet potatoes can be cooked while still frozen for a delicious result.