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Mary Mercado (Lesa Tran Lu); © Natavkusidey | Dreamstime.com (Eggs, Flour); iStockPhoto/Getty Images (Soft Cookie); Shutterstock.com (All Other Images)

I Teach Cookie Chemistry

Lesa Tran Lu has a delicious way to show science is all around us.

By Jacqueline Adams

Learning Objective: Students will summarize how and why a food scientist uses chemistry to invent new cookie recipes.

Lexile: 800L; 570L
Other Focus Areas: Engineering, Matter, Fractions & Decimals

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Cooking Science
Watch a video about the science behind cooking and baking.

Mmm . . . the scent of freshly baked cookies drifts from the oven. You can’t wait to taste one! But have you ever baked a cookie that didn’t turn out how you hoped? Maybe it was too chewy or too flat?

What makes cookies come out perfectly—or not quite right? Often the answer has to do with chemistry, says Lesa Tran Lu. Tran teaches the subject at Rice University in Texas. For one of her courses, she takes students out of the classroom and into the kitchen to put her lessons into practice.

“It’s a fun and delicious way to learn chemistry,” she says.

An understanding of chemistry can help you tweak your favorite cookie recipe—or even come up with a new one! Tran talked with SuperSTEM about some of the baking secrets she loves to teach.

Mmm! The smell of freshly baked cookies drifts from the oven. You can’t wait to eat one! But sometimes baking cookies doesn’t turn out how you hoped. They might be too chewy or too flat.

What makes cookies come out perfectly or not quite right? Often the answer has to do with chemistry, says Lesa Tran Lu. That’s what she teaches at Rice University in Texas. She takes students out of the classroom for one of her courses. They head into the kitchen to put her lesson into practice.

“It’s a fun and delicious way to learn chemistry,” she says. Knowing chemistry can help you tweak your favorite cookie recipe. Or it could help you come up with a new one! Tran talked with SuperSTEM about some of the baking secrets she loves to teach.

Parth Patel (Tran); FatCamera/Getty Images (Child); Shutterstock.com (All Other Images)

Tran demonstrates how to mix a tasty dough.

How did you get interested in chemistry?

I had really great science teachers, and they inspired me to look at, study, and question the world. Chemistry helps explain things around me. That’s what I love most about it. Cooking, painting, the air you breathe, the properties of your chair—that’s all chemistry! It helps you appreciate the things around you.

I had great science teachers. They inspired me to look at, study, and question the world. Chemistry helps explain things around me. That’s what I love most about it. Think about cooking, painting, the air you breathe, or the properties of your chair. That’s all chemistry! It helps you appreciate things in your world.

How does chemistry help you be a better cook?

Cooking and baking involve combining different ingredients and adding energy in the form of heat. This causes ingredients to transform. They undergo physical changes and chemical reactions. If you understand how all this happens, you’re more likely to have delicious results!

You mix different ingredients when you’re cooking or baking. You add energy in the form of heat. This causes the ingredients to change. They undergo physical changes and chemical reactions. It helps to know how this happens. Then you’re more likely to have delicious results!

What is one example of a physical change in baking cookies?

Melting butter is a good example. The butter inside cookies changes its shape in the heat of an oven. Starting with the butter at different temperatures will lead to different results. If you start with frozen butter, it will take more energy and cooking time to melt it. The cookies will be taller and fluffier. If you start with melted butter, the dough will spread faster. Your cookies will be flatter and crispier.

Melting butter is a good example. The butter inside cookies changes shape in the heat of an oven. Starting with the butter at different temperatures leads to different results. Say you start with frozen butter. It will take more energy and cooking time to melt it. The cookies will be taller and fluffier. But say you start with melted butter. The dough will spread faster. Your cookies will be flatter and crispier.

What chemical reactions are involved in baking?

When you bake cookies, many chemical reactions happen inside them. For example, ingredients like baking soda or baking powder react with sugar, milk, or butter. This produces a new substance: carbon dioxide gas. Those gas bubbles expand inside the cookie dough, making it puff up. Baking powder creates more gas bubbles than baking soda—and puffier cookies!

Other chemical reactions occur when you heat up a mixture of sugar, butter, and flour in the oven. These reactions cause cookies to turn toasty brown and smell irresistible!

Many chemical reactions happen when you bake cookies. Take ingredients like baking soda or baking powder. They react with sugar, milk, or butter. This creates a new substance. It’s a gas called carbon dioxide. Those gas bubbles expand inside the cookie dough. That makes it puff up. Baking powder creates more gas bubbles than baking soda. So you get puffier cookies! Heat up a mixture of sugar, butter, and flour in the oven. More chemical reactions happen! They cause cookies to turn toasty brown and smell delicious!

How do you use science to make your own recipes?

 Shutterstock.com

 black sesame macaron

When I develop an original recipe, I use many scientific practices. I start with a question like: How do I make a black sesame macaron? Then I do research using the internet and cookbooks to start with a basic recipe.

Next I design experiments and collect data by baking many batches of black sesame macarons, each slightly different from the last. I might start by using half black sesame flour and half almond flour. Then I might try again with more black sesame flour. I take notes about what I observe and the changes I want to make. I keep baking and tasting until I’m happy with the recipe.

I do a lot of cookie eating in the name of science!

I use many scientific practices to create a new recipe. I start with a question. Like, how do I make a black sesame macaron? A macaron is a type of cookie. Then I do research. I use the internet and cookbooks to find a basic recipe.

Next I design experiments. I collect data by baking many batches of black sesame macarons. Each batch is slightly different. I might use half black sesame flour and half almond flour. I might add more black sesame flour the next time. I take notes about what I observe. I write down changes I want to make. I keep baking and tasting until I’m happy with the recipe.

I do a lot of cookie eating in the name of science!

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