Role of Eggs in Brownies

Figuring out what each ingredient does in a recipe is one of the most valuable things you can learn to improve your baking. There are books detailing the properties of each ingredient. But if you’re anything like me, written facts just disappear from your memory before you’ve even finished reading the sentence. So I thought it was time for some baking science posts where we explore together the role of ingredients with some fun visuals (and a delicious recipe to enjoy of course!). And what better way to experiment than to make lots of brownies!

Today we’ll be exploring the role of eggs in brownies. What happens if you skip them or if you add more than your recipe calls for? We’ll start with a brief overview and then we’ll get into the experiments.

What Are Eggs Made Of?

The three main components in an egg are:

• Moisture: Eggs are primarily composed of water (76%) and are the main source of liquid in the brownie batter.
• Protein: Eggs are made up of proteins that coagulate when heated and provide structure to brownies.
• Fats & Emulsifiers: Egg yolks contain emulsifiers such as lecithin (about 10%). Emulsifiers make it easier to combine fats and water to get a smooth, homogeneous batter. Egg yolks also contain fat which adds richness and flavor.

But I find that the best way to determine the role of an ingredient is to simply omit it and see what happens. So let’s talk first about the most obvious function of an egg when baking.

Moisture/Hydration

Let’s see what would happen if you simply skip the egg:

• Thick batter: The batter will have a paste like consistency that has to be spread with a spoon.

• Grainy texture: Without the moisture from the eggs, the sugar won’t dissolve in the batter and you’ll end up with a gritty, unpleasant texture. You also won’t get to enjoy the shiny crust on the surface of the brownie without enough liquid. You’ll be left instead with a surface full of holes (pictured below).

• Greasy product: The batter (and baked product) will feel very greasy since there isn’t enough water to balance out all the fat added from the butter and chocolate.

• Hard cookie: The lack of moisture in the batter will lead to a dry, almost sandy bar that hardens significantly if slightly overbaked or chilled.

• Overwhelming flavor: The flavor of the butter will be extremely pronounced.

Adding More Eggs To Brownies

Now let’s go in the other direction and see what happens when you add more egg than the recipe calls for.

• More batter: Since you are adding more egg, there will be more batter.

• Cakier texture: Eggs play an important role in the cakey versus fudgy brownie debate. The more eggs you add, the lighter and cakier your brownie will be. We mentioned previously that eggs are primarily composed of water. This water will turn to steam in the oven, helping your brownie rise. The additional liquid provided by using more eggs also contributes to better starch gelatinization leading to a more cakey texture.

What is starch gelatinization? The starch present in flour will absorb the water in the batter and start to swell up and soften with the heat. The batter will then thicken and set, giving structure to the brownies.

• More structure: A brownie made with more egg will deflate less after baking as it can handle its weight better. You can see in the picture below that the brownie made with less egg (control) deflated in the center.

Why do brownies with more egg keep their shape better? Eggs give structure. They are made up of proteins that coagulate when heated. Think of an omelet for example. When you crack eggs into the pan, you start off with a liquid that can easily be spread into the pan. As the eggs get hotter, they start to set and give structure to the omelet, making it easy to transfer onto a plate.

• Stronger egg flavor: You’ll need to add more flavoring to mask any eggy taste if you are sensitive to it.

Egg Yolks versus Whites

Let’s dig even deeper into the role of eggs and see what the difference is between egg whites and egg yolks. To do this, I replaced the amount of whole eggs called for in my recipe with the same amount of egg yolks in one trial and the same amount of whites in another.

• Appearance: All brownies had a thin shiny crust on the surface thanks to the high amount of sugar in the recipe. But the crust was slightly lighter in color when using egg yolks.

• Texture: The texture of the brownies looked more or less the same. But during our tasting, the egg yolk brownies were noticeably drier than the rest when slightly overbaked. On the other hand, the brownies made with egg whites had the runniest batter and had a softer texture, more moist than those made with whole eggs or yolks. When slightly overbaked, the egg white brownies had a crispy crust with a soft crumb.

For the same weight, egg whites (88% water) add more moisture to the batter than whole eggs (76% water) or egg yolks (50% water).

• Chewiness: Brownies made with egg yolks were quite chewy. My daughter called them chewing gum as she was devouring them!

For extra chewy brownies, you could try adding an egg yolk along with the whole eggs called for in your recipe.

• Flavor: Surprisingly, the egg yolk brownies had the worst flavor of the three trials. They had a noticeable egg flavor which was overpowering. The winner was the brownie made with whole eggs closely followed by the egg white brownie. The brownies made with egg whites did feel less sweet than the other ones.

If all this talk about brownies is making you hungry, here’s how to make them!

Step-by-Step Instructions

I’ve been making Nick Malgieri’s supernatural brownies for years and they get rave reviews every time so I had to share this recipe with you.

• Line a square pan with parchment paper, leaving an overhang over the edges of the pan (for easy unmolding). Set aside.

Tip: Use butter if needed to stick the parchment paper to the bottom and sides of the baking pan.

• Place the butter and chocolate in a large microwavable bowl. Heat in the microwave in 20 second increments, stirring in-between, until completely melted. Set aside to cool down slightly.

• In another large bowl, whisk together the eggs and sugar (white and brown) for 1-2 minutes or until light in color. Don’t worry if there is still some undissolved sugar.

• Whisk in the chocolate mixture (that has cooled down), vanilla extract and salt until fully incorporated.
• Add the flour and mix just until combined.

• Pour evenly into prepared pan. Tilt or gently shake the pan if needed to spread the batter. Alternatively, spread evenly with a spatula.
• Bake in a preheated oven until a shiny crust forms on the surface and the batter has firmed up a little. The toothpick test won’t work for this brownie as it is very fudgy. The batter will remain quite wet (unless completely overbaked and dry).
• Remove from the oven and cool completely on a wire rack (in the pan) before cutting.
• To cut the brownies, lift them out of the pan using the overhang. Place on a cutting board and cut as desired. Wipe the knife with a paper towel as needed. Slide a spatula under the brownies (if needed) to release them from the parchment paper.

Tip: These brownies are quite fudgy. You might find it easier to chill them before cutting them.

The baking time will vary depending on the pan you use. The bigger the pan, the thinner the brownie layer and the faster they will bake. Up to you to decide what pan you’d like to use based on availability and how tall you like your brownies. Enjoy!