Extra Yolks

If a recipe only calls for egg whites, don't throw out the unused yolk. Put it in a bowl with a little water over it and cover it with plastic. Keep it in the refrigerator until you use it, which should be within three days.

How to Tell If Your Eggs are Fresh or Expired

Place the egg in a pan of cold water. If it sits on its side, the egg is still fresh. If, however, it tilts on an angle, it's past its prime by about three to four days. If the egg stands upright, it's approximately ten days old. If the egg floats to the top, it's really, really old.