Eggs are used in baked goods for leavening, or lightness. They also may serve as a binder. The purpose the egg serves in the original recipe — as well as the amount of egg the recipe calls for — determines whether you need a substitute and, if so, which alternate ingredient will best serve the function of the egg in the recipe.
Flat foods such as pancakes and cookies don't rely on eggs for lift. In fact, in many cases, you can eliminate the egg without noticeably affecting the final product. That's especially true if the recipe calls for only one egg. If you do omit the egg, however, it's a good idea to add a tablespoon or two of additional liquid — milk, fruit juice, or water, for example — for each egg omitted to restore the recipe to its original moisture content.
When a recipe calls for three or more eggs — as many cakes do — the eggs perform a vital function and need to be replaced with an ingredient that can deliver a similar effect. In recipes for baked goods that have a light, airy texture, replace eggs with an ingredient that provides lift. Any of the following ingredients can replace one whole egg in a recipe:
Half a small, ripe, mashed banana. This substitution gives the food a mild banana flavor, which can be nice in recipes for muffins, cookies, pancakes, and quick breads.
1-1/2 teaspoons of a commercial vegetarian egg substitute, such as Ener-G Egg Replacer, mixed with 2 tablespoons of water. This product is a combination of vegetable starches and works wonderfully in virtually any recipe that calls for eggs. Natural foods stores sell it in 1-pound boxes.
1/4 cup of applesauce, canned pumpkin or squash, or pureed prunes. If you use these foods, know that, depending on the recipe, they may add a hint of flavor. If you want to give the food a lighter texture, add an extra 1/2 teaspoon of baking powder, because using fruit purees to replace eggs can make the finished product somewhat denser than the original recipe.
2 tablespoons of cornstarch beaten with 2 tablespoons of water. This works much like vegetarian egg replacer.
1 tablespoon of finely ground flaxseeds whipped with 1/4 cup of water. The flaxseeds gel and bind with the other ingredients.
Replacing eggs in casseroles, loaves, burger patties, and main dishes -
Some recipes need an ingredient that binds all the other ingredients together. Eggs are famous for acting as the glue that holds meatballs, meatloaf, and casseroles together. Lacto vegetarian and vegan versions of these traditional foods need something to serve the same purpose. Fortunately, you have many options.
As you might suspect, your choice of ingredients to replace eggs in these types of foods depends on the degree of "stick" you need, as well as how the ingredient will blend with the other flavors in the recipe. Cooked oatmeal may work fine as a binder in a veggie burger patty, for example, but may not be a welcome addition to a vegetable casserole if you don't care for the flavor or texture that it brings to the dish.
If you're altering a traditional recipe, you have to experiment a bit to determine just the right amount of an ingredient to serve the purpose. A good starting point with most recipes in which egg acts as a binder is to use 2 to 3 tablespoons of any of the following ingredients (or a combination of them) to replace one whole egg. If the original recipe calls for two eggs, start with 4 to 6 tablespoons of egg substitute.
Whole-wheat, unbleached, oat flour
Finely crushed breadcrumbs, cracker meal, or matzo meal
Quick-cooking rolled oats or cooked oatmeal
Mashed potatoes, mashed sweet potatoes, or instant potato flakes
You can also try 1-1/2 teaspoons vegetarian egg replacer mixed with 2 tablespoons of water.