The (Food) Science of Chocolate Chip Cookies 🍪

Who doesn’t love a warm, gooey, chocolatey-chip cookie? For me, it was the first spark that ignited my interest in food. It always fascinated me that how a soft dough could be formed into a solid cookie just by heat.  But, have you ever really thought about a cookie? What makes it so deliciously irresistible? What reactions might be taking place beneath the surface?

Baking is truly different than traditional cooking. Ingredient amounts must be measured properly to ensure the correct ratios in the final product. The process is just as important as the ingredients themselves in achieving the perfect crumb structure – aka soft and chewy or crispy cookies. Scaling up a recipe can prove very difficult in baked goods. Baking is a science! And a delicious one at that.

Thinking like a scientist, let’s break down the recipe step by step. A typical chocolate chip cookie is made of ingredients like eggs, flour, and sugar, but what role does each of these ingredients play? Do you really need all that sugar? Let’s take a closer look.



Wheat flour contains proteins that provide structure to the cookie. This makes the cookie soft and chewy or crisp and hard. Ever heard of gluten? This is the protein that creates a strong network in the product. The individual proteins glutenin and gliadin interact with one another to form strong bridges as the dough is mixed. The amount of flour in the cookies is a big deal. Higher amounts of flour allow more gluten development, and thus a tougher cookie.


This ingredient acts as an emulsifier. That means it acts to suspend fat in a liquid. You may know that oil and water don’t mix, but emulsifiers help them become friends! This keeps all ingredients bound together to create a cohesive dough. Eggs also act as a source of protein in the product for other chemical reactions and as a source of moisture.


Both white granulated sugar and brown sugar are used in many cookie recipes. Each of these sugars provides sweetness and volume to the dough. The sugar also reacts with proteins in the egg and flour to create the characteristic golden brown color of a cookie. This is known as the Maillard Browning Reaction. Sugar also browns via a caramelization reaction. This is the same reaction you may have seen when sugar is directly heated on the stove to create candies. Finally, sugar also binds water. This means that cookies with more sugar will be more crispy due to a lower availability of free water.


Butter acts as the fat source in the product. This is critical to the mouthfeel and tenderness of the cookie. To put this is perspective: it contributes to how moist and smooth the cookie feels in your mouth. Some recipes may substitute vegetable oil for butter, which creates a very different type of cookie. Butter also controls the amount of gluten formation in the flour (see above) to ensure the dough does not become too stiff. Proteins become coated in fat and decrease the amount available to form the gluten bridges we discussed earlier.

Baking soda

Also known as sodium bicarbonate, baking soda provides just enough leavening to the dough to allow your cookies to rise in the oven. Baking soda is a type of chemical leavener that creates carbon dioxide gas bubbles as it reacts with acid in the dough. This ingredient is common in many baked goods.


Acts as a flavor enhancer in the cookie.


Flavor enhancement.

Did you know? Salt enhances the perception of sweetness in any recipe! This gives your cookies flavor dimension.


And, of course, chocolate chips for delicious, melted goodness!!

So, as you can see, each ingredient plays its own critical role in the cookie. Fascinating, right?! Who knew there was so much chemistry going on in your oven. Now, let’s think about the rest of the recipe. There’s more to it than just the ingredients. In baking and many recipes, the process matters too.


The first step in any recipe is to cream the butter and sugar. This creates air pockets in the dough. Remember our discussion on baking soda? The pockets created from creaming are necessary for the carbon dioxide created by the sodium bicarbonate to escape, causing rise in the cookie. So the next time you are making cookies at home, remember not to skip this step!

Once creaming is complete, the flour and dry ingredients can be added and mixed. This mixing is what creates the gluten network in the dough and leads to the structure. It also ensures all ingredients are well combined.

After the dough is complete, it’s time to head for the oven!


To get a better understanding of what’s really going on in that oven of yours, let’s take a closer look inside.

Chemical Reactions of Cookie Dough Infographic
cookie experiment

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