Many recipes use egg yolks only, so you sometimes need to store leftover egg whites. Of course, you can keep them in the fridge for a few days but you must to spend them as soon as possible. Your problem is solved, if you freeze egg whites you don't need right away.
Egg whites can be frozen successfully for up to a year, but you must treat them right from the time you freeze them to the time you thaw them and use them.
It's the best to pour each egg white into separate compartments of an ice cube tray. Place the ice cube tray in the freezer and freeze until firm then transfer them to a zip-top freezer bag or freezer-safe container and return to the freezer for up to 1 year.
Once, you need them you have them ready. Just thaw as many cubes as needed in the fridge overnight. Leave them at room temperature for about 30 minutes, before whipping. Otherwise, they should be used right after they are thawed. Thawed egg whites are also best used in things you intend to cook or bake.
There are so many recipes using only egg whites, from cakes, cookies or frittatas. We have a collection of recipes for Italian amaretti cookies using only egg whites - classic, chocolate and hazelnut amaretti. Why not to try our soft chocolate hazelnut cookies, brutti ma buoni or Sicilian almond cookies.