Science of Baking – Eggs

What does a specific ingredient do to a recipe? This is what I’ve wondered almost everytime I have leisurely flipped through my cookbooks. It explains why I am a Foods and Nutrition major. I’m interested in the science of food and how everything in a recipe comes together to create something so delicious!

The last recipe I posted, the Chocolate Chip Cream Cheese Cookies, was an original recipe I created and I pondered for several minutes while producing this recipe whether I should add in one egg, two eggs, or any eggs at all! I had to revisit my food science notes to pinpoint the purpose of an egg in a cookie recipe.

What do they do?

Eggs are made up of several proteins and cholesterol. There is about 7 grams of protein and 200 milligrams of cholesterol in one egg. Eggs serve as emulsifiers and binders in food as well as providing a source of leavening and structure. An egg added to a batter helps bind the other ingredients together while adding more moisture. This results in a smoother batter.

When the mixture containing egg is heated, the moisture provided by the egg heats and creates gas bubbles and steam. The steam builds up within the product being baked, is trapped within and creates air pockets. Air pockets equal structure. More structure produces a light and fluffy baked good.

Purchasing and Preparing

One way to tell if you are purchasing good quality eggs is by looking at the grade given by the USDA. Grade AA and Grade A are the highest quality. It means the batch of eggs contain a large, firm yolk and a thick, clear egg white which will result in a well structured cooked egg. A Grade B egg contains a flat yolk and a loose, watery egg white.

When cracking open eggs in preparation of a recipe, they should be opened over a separate bowl. Cracking an egg open over your baking mixture means you are risking egg shell pieces turning up in your finished product. No thanks. Crack your eggs over a separate bowl, make sure there are no egg shell pieces, and finally add your eggs to your batter as the recipe instructs.

While the cookies turned out very delicious, I feel that if I had omitted the egg, the cookies would not have turned out as cake-like and would have flattened more while baking. It’s something I want to try the next time I create the cookie recipe to see the result.


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