What makes cookies bind together when they are baked?

There are several factors that contribute to cookies binding together when baked:

1. Gluten Development:

* Flour: Flour contains gluten, a protein that forms long strands when mixed with water. As the dough heats, the gluten strands strengthen and create a network that holds the cookie together.

* Mixing: Overmixing the dough can develop too much gluten, resulting in tough cookies. Conversely, undermixing can lead to crumbly cookies.

2. Sugar:

* Granulated sugar: It dissolves in the dough and provides sweetness. As it heats, the sugar caramelizes, creating a sticky texture that binds the cookie.

* Brown sugar: Contains molasses which provides moisture and helps with browning.

3. Fats:

* Butter, shortening, or oil: Fats provide texture, richness, and moisture. During baking, the fats melt and create air pockets that contribute to the cookie's structure.

4. Eggs:

* Egg whites: They contribute to structure and binding, and also create a light and airy texture.

* Egg yolks: They provide richness and color.

5. Temperature:

* Baking temperature: The heat of the oven promotes gluten development, sugar caramelization, and fat melting, all of which are essential for binding.

6. Baking Time:

* Correct baking time: Baking for the appropriate duration allows the ingredients to fully interact and solidify, creating a well-bound cookie.

7. Other Factors:

* Baking soda/powder: These leavening agents create air pockets that help cookies rise and develop a lighter texture.

* Liquids: Milk, water, or other liquids provide moisture and help the ingredients bind.

* Other ingredients: Nuts, seeds, chocolate chips, etc. can contribute to the texture and structure of the cookie.

It's the combination of these factors that results in a well-bound cookie. The relative proportions of each ingredient, along with the mixing technique and baking temperature, all play a role in the final texture and appearance of the cookie.