Science Explanations

Oh My Brownie & The Impact of Eggs

Within this section of the blog, we will explore the science of baking brownies. Before tackling the brownie recipe and adaption, we must first examine the roles of each ingredient for Brownies. Below I have included a chart that explains the role of each ingredient:

Function Of Ingredients:

  • The Purpose of butter is to free fat to stick in larger masses and is classified as a water-in-oil emulsion. When melted and creamed with sugar, it’ll coat the sugar granules instead of trapping small air bubbles. Butter also separates out the water, allowing for more gluten to form.
  • Butter has 80% of fat in it and when baking brownies the fact content plays a large role in making brownies. Blending fat with flour impedes or shortens the web of gluten fibers that makes dough cohesive and elastic. The high percentage of baking fat in brownies is one factor accounting for the tender, crumbly texture of a good brownie. Butter, used hereafter as a generic designation for fat, may also play a role in raising brownie dough (
White sugar
  • The purpose of white sugar is to contribute to crust formation. This is a result of caramelization that causes the surface of the brownie to become brown.
  • The purpose of eggs is to keep the brownie together and contribute to the fat and moisture of brownies.
Vanilla extract
  • The purpose of vanilla extract is to enhance the flavors of the other ingredients 
All-purpose  flour
  • The main purpose of all-purpose flour is to build the structure. When the proteins found in flour are hydrated they form gluten. As batter containing flour is mixed together, an elastic network is developed. This gluten network stretches to contain the leavening gasses in the baked good. Flour and the production of gluten is essential for the structure of traditional baked goods
  • The purpose of salt is to build up the flavor of other ingredients.
  • Increases the color of the crust
Baking powder
  • The purpose of baking powder is to produce carbon dioxide that will introduce air in the brownie, making it more airy and fluffy. 
Unsweetened cocoa powder
  • The purpose of unsweetened cocoa powder is to add a deep chocolate flavor 
* For more information on the ingridents and how they tie together click on the following links

Background on Eggs/ Denaturation:

The beating of eggs is a way to denature the proteins that are within them. Denaturation is the alteration of a proteins’ natural structure by chemical or physical means. Proteins are long chains of amino acids, so when they are denatured they are unraveled. The previous bonds are then available to bond with other molecules. However, there is only a change in the structure of the protein not a change in composition. The original state of the protein resembles curled-up little balls, which have hydrophobic parts. As we know, eggs provide the gooey like texture because they contributing moisture and fat. As a result, the egg within the mixture will cook. That is because of protein coagulation, where the proteins will form and bond together.  Below I have included a chart that displays the protein coagulation that occurs within an unmixed egg. However, since we are dealing with a mixed egg in the recipe, coagulation will occur between 144° F and 158° F (62.2° C and 70° C).

145ºF egg white begins to thicken
150ºF egg white becomes a tender solid 
150ºF yolk proteins begin to thicken
158ºF  yolk sets
165ºF yolk and white mixed together sets
180ºF ovalbumin begins to thicken
184ºF  ovalbumin sets
*For more background on the science of eggs click on the following link*

Recipe Adjustment:

The original brownie recipe calls for the use of  2 eggs. An adjustment that I made was to change one of the 2 eggs to egg whites. I wanted to see how changing the components of an egg would affect the overall texture of the brownie. Brownies normally have a  chewy and soft texture, so after completing this investigation I saw how much of a role eggs play when making brownies. By adding eggs whites to the batter the structure of the brownie changed from moist and chewy, to a cakey like texture. This occurred because egg whites make up 58% of the egg. An egg is mainly composed of  88% of water, 0.2% fat, and 11% of protein. The protein in egg whites is where all essential amino acids are found that are rearranged through denaturation and coagulation. Egg whites begin to solidify and cook faster due to forming at a lower temperature. This would cause brownies to form faster while letting moisture escape at a faster rate. So the number of egg whites present within the adapted recipe is greater than the original recipe, and therefore overpowers the number of protein provided from the one yolk to even out. According to Taste Of, “Egg whites add volume and act as a drying and leavening agent. Egg yolks provide fat, which adds flavor and tenderness, and protein… The yolk also acts as an emulsifier, helping to blend liquids, like oil and water, that are hard to combine.” Since the adaption is switching from two mixed eggs to one mixed egg and an egg white, there will be a loss of fat content. The loss of fat content will result in the brownie having a lighter, airier texture because of the decrease in fat. A good rule of thumb to remember when dealing with eggs is that more egg whites create a firmer consistency and more egg yolks create a creamier consistency.  An adaption like this would be helpful for people who prefer cakey brownies, so this was a nice insight for that. Cakey brownies are thicker than the original brownies and have a lighter, airier texture due to a lower amount of fat. 

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