It's the most common ingredient in salad, and it adds that nice crisp "crunch" to deli sandwiches, but lettuce isn't tasty at all once it goes bad. As a refrigerated vegetable, lettuce has a one-week shelf life when sold unpackaged. For packaged lettuce, the "use by" date indicates how long the lettuce stays fresh unopened. Once you open the package, the lettuce begins to age, and you must look to warning signs of spoiling ---- not the date on the bag ---- to determine if the lettuce still is good to eat.
Pull off the first layer of leaves, which you do not eat.
Check the remaining leaves for wilting or browning. The leaves should either be green or reddish purple, depending on the type.
Feel the lettuce. It should feel crisp, not slimy.
Look for swelling or moisture in a bag of packaged lettuce, a sign of spoiling that can cause mould to grow.
Refrigerate lettuce at 35 to 40 degrees Fahrenheit. Wash the lettuce thoroughly and cut off the outside layer before eating.
You cannot remove bacteria simply by running lettuce under cold water. When in doubt, throw the lettuce out.