what is the purpose of egg wash in baking
Egg wash An egg wash is often used to make pastries shiny and golden or brown in color, and it also is used to help toppings or coatings stick to the surface of the pastry, or to bind pastry parts together, such as empanadas or other en croute recipes. Egg wash can usually be made with 30 ml or two tablespoons of liquid, such as milk or water, for every egg. Less liquid makes for a darker wash.[3] The part of the egg used and liquid added determines the finished look of the crust.[4]
Yolk Among animals which produce one, the yolk (also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some kinds of egg contain no yolk, for example because they are laid in situations where the food supply is sufficient (such as in the body of the host of a parasitoid) or because the embryo develops in the parent's body, which supplies the food, usually through a placenta. Reproductive systems in which the mother's body supplies the embryo directly are said to be matrotrophic; those in which the embryo is supplied by yolk are said to be lecithotrophic. In many species, such as all birds, and most reptiles and insects, the yolk takes the form of a special storage organ constructed in the reproductive tract of the mother. In many other animals, especially very small species such as some fishes and invertebrates, the yolk material is not in a special organ, but inside the ovum.