COOKIE SCIENCE

Most cookie recipes call for eggs and butter. These ingredients contain water. For sweet success, it’s important to mix the wet ingredients together with sugar in one bowl. Sugar absorbs the water, and brown sugar absorbs even more. The result will be moist cookies that you can sink your teeth into.

Cookies also contain dry ingredients like flour, salt, baking soda, or baking powder. You’ll want to combine these in a separate bowl so the dry ingredients get as perfectly mixed as possible.

Next, you’ll add these dry ingredients to the wet mixture. That will start a chemical reaction! When two types of protein in the flour get wet, they form a mesh-like structure. The more you mix the dough, the tougher this structure becomes. Don’t mix it for too long, or you’ll end up with tough cookies, though, says Tran.

Finally, it’s time to add fun ingredients, like chocolate chips. Or you can test out more unusual ones—like potato chips or pretzels!

When you pop the dough into a hot oven, the butter melts. This is a physical reaction. The cookies spread out. But they also rise. That’s because gas bubbles are forming inside the dough. The bubbles are a result of water in the eggs and butter changing from a liquid to a gas. Also, baking soda reacts with brown sugar to form carbon dioxide gas. If you use baking powder, heat will cause it to release even more carbon dioxide bubbles. As these bubbles rise, the mesh-like structure of the flour keeps them inside the dough. They can’t escape, so the cookies puff up.

The oven’s heat triggers more tasty chemical reactions. Sugar breaks down and combines with other ingredients to make a sweet caramel flavor. Sugar also reacts with the proteins in the flour. This browns the cookies and creates toasty flavors.

When should you take the cookies out of the oven? “The best indicators are your eyes and nose,” says Tran. You’ll smell the sweet, toasty scents and see the cookies turn golden brown. That means these reactions have done their job.

Now you can experiment for different results. Do you like soft, moist cookies? Use more brown sugar than granulated because brown sugar absorbs more water. Do you want your cookies to be puffier? Use baking powder instead of baking soda. It creates more gas bubbles.

People have different tastes. That’s why there isn’t one perfect cookie recipe. “But if you use science, you can develop your own perfect recipe,” says Tran.