Cooking is Chemistry

Cookie science from Jake Lucas on Vimeo.

First attempts in any kitchen are filled with frustration. Seemingly harmless discrepancies, from recipe to mixing bowl, come out of the oven as unacceptable in the eyes of our own self-judgment.

Some scoff at the need to be meticulous. Others get fed up with the magic touch that seems to lie between the lines of recipes.

In truth, cooking is chemistry. Understanding that chemistry deflates the mystery from cooking and offers a harmless introduction to the mysteries of science.

“The kitchen really is a lab, and we’re all food scientists when we enter the kitchen,” said Valerie Ryan, who writes for the food section of the Boston Globe and holds a Master’s degree in Gastronomy from BU.

This summer, Ryan is teaching a course about the science of food and cooking at BU.  It discusses the science behind different kinds of food and what happens at every step of preparing and cooking food.

“Food is made up of molecules, and if we understand how we’re manipulating those molecules, then we can become better cooks,” Ryan said.

From the moment ingredients are mixed together in a bowl, their molecules start colliding into each other, breaking apart and forming new compounds. Adding heat further breaks down those molecules and introduces whole new flavors.

Ryan said baking cookies is one of the best examples of many of cooking’s most important chemical processes.

“If you take the example of cookies, it really starts when you’re mixing.” Much of how a cookie comes out of the oven is determined by how much gluten is allowed to form, she explained.

Gluten is a composite of proteins that forms when flour interacts with water. While it gives structure to dough and batter, Ryan said too much gluten makes baked goods tough and chewy.

In the case of cookie batter, both sugar and fats like butter and shortening keep water from interacting with flour. Sugar competes with flour for moisture, and binds to it more readily than flour, so it usually wins out.

Cookies straight out of the oven! | Photo courtesy of wikimedia user Kari Sullivan.

What’s more, Ryan explained, “Fat molecules interact with the protein in the flour and essentially get in the way of gluten development.” That helps explain why some of the best cookie recipes call for the flour to be added last, leaving it with the last of the moisture and time only to form as much as is necessary to keep the cookie together.

When the cookies go into a pre-heated oven, all of those compounds continue to interact in delicious ways, and sugar particularly plays a couple of important roles.

“Sugar is something that really impacts the texture of the cookie,” Ryan said. “It can make it more tender, and…it can make it more chewy.”

On its own, some of the moisture the sugar absorbed in the mixing process gets evaporated, recrystallizing the sugar and making the cookies crispy. Some of the sugar is also caramelized, turning it brown and giving it a nuttier, caramel-like flavor.

Sugar is also involved in what’s known as the Maillard reaction, named after French chemist Louis-Camille Maillard.

“It’s a really important reaction in food,” Ryan explained. “When you cook something that has both sugar and protein, those interact with each other. You get browning, and the byproducts of browning are flavor compounds.”

Ryan said even after decades of studying the Maillard reaction, we still don’t understand all it can do. What we do know, she said, is that it can create more than a hundred new flavor compounds.

As the cookies sit baking in the oven, macromolecules like protein and carbohydrates are also breaking down and introducing new flavors. The carbohydrates in flour, for example, are breaking down into the sugars they’re composed of, and those sugars also caramelize.

Ryan said many of the tastiest foods, like cookies, are highly chemically active. Another example is a well-cooked steak. Cooking a steak properly unleashes caramelization and the Maillard reaction, and the break down of all kinds of macromolecules  making it tender.

While knowing what’s going on chemically in the kitchen hasn’t dramatically changed the way Ryan cooks, she did say it helps.

“Just knowing a few things about kitchen chemistry makes me fine tune what I do. It’s not necessarily that I’m making huge changes, I’m just fine-tuning. And then what I cook is better. It’s more delicious.”

About Jake Lucas

Hi there I'm Jake. I'm a journalism major/environmental policy and analysis minor originally from the suburbs of Chicago. I'm interested in all kinds of science, politics and economics. I also like bears, singing and podcasts. If you have any questions, tips or just want to shoot the breeze, email me at Or, find me on Twitter @JakeDLucas.

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