What causes hard skins on baked eggs?
I know one of you kitchen whizzes will know this. When you bake a whole egg, such as in a muffin cup, what causes the hard, shiny surface? It's almost like cellophane and shiny? I know it must be related to why people use an egg wash to give a shine to a food, but I'm interested in the chemistry behind it, should anyone know. It's pretty, but a bit tough to then cut through to eat.
This would also be the same thing that happens on the edges of fried eggs. Good question...
My *guess* is that the egg white, which is mostly water and a bit of protein, simply dries out. By cooking the egg you're evaporating some of the water, right? So what you're left over with is clear, hardened protein on the surface that was most easily evaporated... the top. Next time you're preparing eggs, do an experiment; put a few drops of egg white on a plate and set it aside for a day or 2. That will allow the water to evaporate and my guess is that you'll end up with the same result.