One of the more frustrating things about using romaine lettuce for salads and other dishes, is keeping it from turning brown, especially after you've cut it. No one wants to eat brown lettuce, but keeping it green and vibrant until you want to eat it is often challenging. It will usually last for seven to 10 days with the right storage, but you must follow the proper handling guidelines if you want to avoid browning.
Rinse, Dry and Store
To keep your romaine fresh and keep the brown away, tend to it as soon as you bring it home from the store. Separate the leaves from the core with your hands and rinse them off well under cool water. Place the leaves in a salad spinner and spin vigorously until they are dry. Store the dry leaves in a sealed plastic container or tightly sealed plastic bag away from air and moisture until you're ready to use them.
Postpone the Cutting
If your dish calls for cut or chopped romaine lettuce and you've had issues with premature browning, try waiting until the last possible moment before cutting it up. Assemble the rest of the ingredients and then cut up your lettuce just in time to mix everything together and serve. Store leftovers that contain romaine in an airtight container in the fridge to keep them fresh longer, but eat them as soon as possible.