Egg yolk makes up the other one-third of the whole egg and contains a high percentage of fat as well as some protein and water. When a recipe calls for only yolks, it is typically because the fat content, as well as the yolk’s ability to emulsify, is desired.
- Add Richness: Egg yolks add richness to baked goods due to the fat content.
- Emulsify: Egg yolks are great emulsifiers, meaning they work to combine water-based liquid and fats into one cohesive mixture. This function helps create a smoother and more homogeneous batter or dough.
- Enhance Color: Egg yolks add flavor and color.
- Thicken Mixtures: Egg yolks also thicken mixtures when they are heated because the proteins begin to gel. You will see this very clearly when making custards like pastry cream or fruit curd.