Baking cookies is almost magical. You put little balls of wet, white dough into the oven and out pop brown, crispy, tasty biscuits.
"In a time-lapse video, it looks like a monster coming alive," says the team from TEDEd in a new animation that — just in time for the holidays — explains the science behind great cookie baking. "For a moment, it [the raw dough] sits there innocuous ... then it bulges outward ... it triples in volume. Its color darkens ominously. And its surface hardens into an alien topography of peaks and craters. ... The kitchen timer dings: Your cookies are ready."
So what's going on in that oven? How does the heat make our snickerdoodles and chocolate chippers so delicious?
It's all about the chemistry.
"Don't let that apron deceive you. Bakers are mad scientists," the narrator of the animation says. "When you put the raw cookie dough into the oven, you're setting off a series of chemical reactions."
By playing around with the ingredients in your favorite recipe, you can tweak these reactions and engineer your ideal cookie. For instance, you can make it chewier, fluffy or thinner.
We'll get to that part in a moment, but first, let's take a look at the three major steps of the cookie-baking process:
All this baking chemistry provides the building blocks for refining the cookie's architecture, says molecular biologist Liz Roth-Johnson, who runs the Science and Food blog at the University of California, Los Angeles.
"Say I have a cookie recipe, and it's not quite what I want," she says. "You can take these basic concepts and use them to engineer the perfect cookie."
Take, for instance, the cookie's diameter. Its size depends on how quickly the dough spreads out as the butter melts in the oven.
"If you start off with melted butter in the raw dough — instead of cold butter chunks — the dough is immediately wetter and will spread out faster," Roth-Johnson tells The Salt. The result is a flatter, wider cookie.
But the butter's temperature will also affect the cookie's texture. It changes the air pockets left behind as the water in the butter converts into gas, Roth-Johnson explains.
Melted butter creates smaller and more holes. That makes for a chewier cookie.
"On the other hand, if you incorporate chunks of cold butter into the dough, you get larger pockets of air and a fluffier, cakier cookie," she explains.
You can also switch out the baking soda for baking powder for a fluffier treat. "The powder gives the cookie an extra kick of leavening," she says, "because it produces carbon dioxide gas both when it's mixed in the dough and when it heats up."
To make a thicker cookie, Roth-Johnson says, try using more flour.
Finally, you can pump up the cookie's flavor and aromas by spiking the dough with dark sugars. White granulated sugar doesn't participate very well in the Maillard reaction because it contains mostly sucrose. Darker sugars — like molasses, honey and brown sugar — are packed with glucose and fructose, which are happy to churn out rich, complex tastes from the Maillard reaction.
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