Many recipes call for an egg wash -- brushing dough with beaten egg -- just before baking to create a shiny, richly colored crust. While this is an important step, it is possible to create satisfactory results without an egg. To determine the best alternative for your dish, it's important to understand what each substitute does.
The Purpose of Brushing Dough
Glazing dough before baking imparts different effects, depending on the glaze. Protein in a glaze contributes to browning the crust, while fat content increases overall shine. Whole eggs are rich in both protein and fat, which gives the finished product a deep golden shine. Egg washes are also important to make other items stick to the surface, such as seeds or decorative dough cut-outs.
Aside from eggs, ingredients traditionally used in glazing bread or pastry items include milk, cream, water, oil, butter or nothing at all. Because milk is also rich in protein, it gives a golden color but lacks the shine that egg washing provides. Butter or cream create softness and shine, but these don't brown quite as well as milk or eggs. Water glazing, creating steam or spraying with water periodically during the baking process create the crispiest crust of all.
Brushing After Baking
Another option is to glaze with nothing at all during the baking process, then to brush the finished product with oil or butter. This will provide shine and softness to your finished loaf. Another trick is to brush with oil or butter before baking, then again when it comes out, creating an even softer and chewier dough. While this won't create the thickness and shininess of crust baked with an egg glaze, it will give you some of the same benefits.
Gluing It Together
If your biggest concern is getting ingredients such as nuts, seeds or dough cut-outs to stick, stay away from oil, butter and cream because these are naturally slippery. Water or milk will work best in getting those little details to stick, scoring the dough underneath if you are working with cut-outs. Press the toppings on firmly before baking, and everything will stick even without the egg wash.