An egg white wash promotes browning on baked goods. You don't add an egg white glaze to every baked good -- only to ones that you want to have a crisp, matte surface. The surfaces most often glazed with the egg white are:
- pie crusts
- puff pastry
- and bread loaves.
Egg white can sometimes feel gooey and thick when you work with it as a glaze. A pastry brush and the addition of salt helps make the glazing process more manageable.
If you want a shiny gloss on your finished product, such as with a challah loaf, glaze with a whole egg beaten with a few pinches of salt.
The protein in an egg white promotes browning. Because there's no fat in the white, it won't bake a sheen into a pie, bread or pastry. For a matte, well-browned surface, add a pinch of salt to the egg white -- about 1/8 teaspoon per egg. In addition to promoting browning, salt also thins the egg white slightly, making it easier to apply. For most baked good recipes, one egg white is enough. You can also glaze with just egg white -- no salt added -- which will result in a crispy, paler crust.
Whether you're adding salt to the egg white or not, beat it vigorously to reduce its viscosity and make it easier to apply evenly.
Once you mix them together, give the salt a minute or two to start the breakdown of the protein in the egg whites so the mixture thins and becomes easier to apply.
A natural-bristle pastry brush is most effective in creating an even, thin glaze application. Dip the brush in the egg wash, let any extra drip off and then brush the top of the dough with a light touch in even lines. A little wash that drips down the side is OK for most baked goods, but you don't need to apply the wash to the entire item -- only the top surface. Apply wash carefully when your dough is in a bread pan; egg white wash can seal the bread to the sides of the pan. Keep the layer of wash thin to prevent this from happening.
When applying a wash to flaky pastry dough, such as puff pastry, concentrate the application on the very top only and avoid all drips. If you allow the egg white to ooze down the sides, it can glue the layers of pastry together and prevent them from rising to their optimal height.
Wash the brush immediately after use to prevent egg residue from drying in the bristles. Once it's dried, cleaning is much more difficult.