Butter Isn't Quite The Egg Wash Substitute You Think It Is
Whether you're baking a fresh batch of dinner rolls or a homemade pie, it won't be complete until you brush the top with egg wash before it goes into the oven. Skip this step, and the pastry will still taste perfectly fine, but it won't have a shiny, golden finish. If you don't have any eggs on hand, your first thought might be to reach for melted butter instead, but the truth is, it won't have quite the same effect.
Egg wash works because it's made of protein and fat. The fat in the yolk is largely responsible for the shine, while the protein in the whites promotes browning. To make it easier to brush onto pastries, egg wash typically calls for a splash of water as well. But oftentimes, milk and heavy cream are used for an extra boost of protein and fat. Even though butter is commonly used in place of egg wash, it's made up primarily of fat and contains little protein, meaning it's not the most effective at browning.
What happens when you use butter instead of egg wash?
When you use butter instead of egg wash, your baked goods will still have a noticeable sheen to them, thanks to the fat in the butter. However, they'll be even paler than they would be if you were to opt for no butter at all. The reason is that rather than sitting on the surface of the dough and forming a crust, the butter simply soaks into it.
The advantage to using butter instead of egg wash is that it yields a tender texture. This may not be something you'd want if you're aiming for a crusty exterior, but it can be beneficial for breads that call for an extra soft, pillowy texture. Butter also has a much more rich, decadent flavor compared to egg wash. But if you want that buttery taste without the softness, you'll want to brush it on after it's done baking instead of before, the way you would with egg wash.
Better egg wash alternatives
While using butter in recipes that call for egg wash certainly won't ruin the end product, there are other alternatives that have effects that are more similar to the real thing. Mayonnaise — though it may be the last thing you'd probably think to put on a baked good — actually produces the same glossiness and color as egg wash. That's because despite being a sandwich condiment, it's made up of egg, oil, and vinegar, giving it the perfect amount of protein and fat for an egg wash substitute.
Mayonnaise won't affect the taste of your pastries once baked, however if the idea doesn't sound appetizing, yogurt is an equally effective option. It's high in fat, so it'll produce a shiny finish. But unlike butter, it's also packed with protein. As a result, yogurt has similar browning effects as egg wash, which means you'll want to reach for it over butter if you don't have any eggs.