Eggs' Purpose

• Eggs play a critical role in cakes, including those made with cake mix. The whites contain protein, which acts as a building block, forming the structure of the cake so it's not a gloppy mess. The yolks contain fat and lecithin. Fat adds flavor to cakes and also helps increase tenderness. Lecithin is an emulsifier. It coats dry ingredients, allowing them to blend smoothly so the cake batter has a creamy, velvety texture.

Weird Science

• Cake mixes have been tested and retested to withstand almost any torture you can dish out. However, they're not completely indestructible. Reduce or increase the number of eggs in a cake mix by just one and you probably won't notice much of a difference, but if you alter the recipe too much, you'll probably be disappointed with the results. Adding more egg whites can create a dry, tough cake, while adding a lot of egg yolks may make a cake too soft. Decreasing either creates the opposite effect. Decrease the egg whites and the cake won't firm up well; decrease the egg yolks and the cake becomes crumbly or tough. Adding or deleting whole eggs may cause a funky combination of symptoms.

Simple Substitutions

• Read the cake mix label before you reduce or increase the number of eggs. Most cake mixes offer suggestions on reducing or replacing whole eggs with egg whites or an egg substitute product. To prevent dryness when reducing eggs, try adding other ingredients known to provide moisture, such as a few tablespoons of applesauce, Greek yogurt, sour cream, melted butter or dry pudding mix.

Size Matters

• The number of eggs in a cake batter isn't the only consideration. You should also pay attention to the size of the eggs. Most cake recipes are written for large eggs, or eggs that weigh about 2 ounces in the shell. If you have jumbo or extra large eggs, you can use about one less egg. When using medium or small eggs, though, you may need to increase the number of eggs you use.