Chemistry in Cookies

Author: Demi Leng

Editor: Tharindi Jayatilake

Artist: Aurora Chen

What is the first thing that comes to mind when you think of chemistry? The periodic table? Experiments? Explosions? What about baking? Have you ever linked those crispy biscuits or delicious cupcakes with chemistry? It is hard to relate these sweet desserts with this tough subject (well, at least for me). You may be surprised to learn that the secret of turning a dough into a tasty cookie in the oven is all about chemistry.

So what happens in the oven? Before you put the dough in the oven, it isn’t a cake. But when it gets baked in the oven, a chemical reaction will occur and new bonds will be formed. The heat creates these chemical reactions. When it comes to heat, there are two types of reactions to consider: exothermic and endothermic. Exothermic reaction releases heat, and by contrast, endothermic reaction absorbs heat. Your uncooked treat is experiencing an endothermic reaction in the oven.

As you might know, water evaporates at 100°C, which is 212 °F. When the cookie dough reaches this temperature in the oven, the water inside will turn into steam and the cookie will therefore start to rise as vapors push through the dough. The baking soda and other powders will break down into carbon dioxide gas (CO2), which pushes the cookie to expand upward even more. This carbon dioxide gas creates small holes in the cookie which is the reason why cookies are light and flaky.

Why would a white dough turn to a brown cookie rather than a white one? A process called caramelization happens as the dough gets heated in the oven, the sugar inside breaks down and transforms from clear, odorless crystals into brown, fragrant liquid, turning the cookies brown.

You may or may not realize this, but science is everywhere in your daily life. Baking is just an example of where science could hide. What you learn in the classroom is just a very small portion of science, so go on and explore more every day and you might see the fun in it that you never realized before.

Citations:

Doucleff, Michaeleen. “Cookie-Baking Chemistry: How To Engineer Your Perfect Sweet

Treat.” NPR, NPR, 3 Dec. 2013,

www.npr.org/sections/thesalt/2013/12/03/248347009/cookie-baking-chemistry-how-to-

engineer-your-perfect-sweet-treat.

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