The protein in egg yolks allows them to serve as binders, or stabilizers, in baking and cooking. When mixed in a correct ratio with other ingredients, the coagulation of the yolk's proteins helps bring the recipe together and create the necessary structure for the dish. They also aid in incorporating and distributing air in the recipe to create an even binding of ingredients. If the primary function of the yolk in a recipe is to help with structure, such as in a custard, mousse, or quiche, replace the egg with another ingredient high in protein. Silken tofu, coconut milk, cashews ground to a very smooth cream, agar powder and chickpea flour mixed with water all work well as substitutes.

When egg yolks are whipped in a recipe, they trap air. The air then expands during cooking, which creates volume and lightness. This leavening power can be achieved with other ingredients such as chickpea flour mixed with water, silken tofu, or flaxseeds blended with water to a smooth and creamy consistency. For recipes in which the egg yolks serve as a binder or thickener as well, you can use ingredients that don't have leavening power as long as you add a small amount of baking powder -- about one-half teaspoon. Bananas, applesauce, and non-dairy yogurt all work for this method. For baked goods, such as cookies and cakes, substitute about two tablespoons of white or apple cider vinegar and an extra one-half teaspoon of baking powder for the egg yolks. The vinegar will not be noticeable, and you will achieve the same leavening and binding effects.

The same coagulation of egg yolks that helps create structure in recipes also serves to thicken them. Fortunately, there are plenty of ingredients that can be used as substitutes for egg yolks when the primary function is as a thickener. Tofu, both soft and firm, works for everything from smoothies to frittata to custards. Pureed avocado, with its mild flavor, also serves as a thickener. Coconut milk, soy flour, cornstarch, coconut milk, nut butters, and chickpea flour all fill the role, as well.

In many recipes egg yolks also enhance the finished dish's flavor because of their fat content. The richness that the yolks add is easily mimicked with a number of ingredients, from coconut milk to avocado to additional butter. Adding canola, olive, avocado, peanut or sunflower oil replaces both the moisture and flavor of the egg yolks. When substituting for egg yolks with any liquid, remember to retain the ratio of wet to dry ingredients. You may need to add a small amount of additional dry ingredients to account for the shift.