The Chemistry of Baking Cookies
News & Other Stuff 5
Want to wow your chemistry teacher? Bring in a batch of chocolate
chip cookies. No, it’s not about being the teacher’s pet. It’s about enjoying the tastier side of science.
Baking is all about chemistry and if you’re looking for a way to experience it first-hand, the chemistry of
baking cookies the best way to go.
“When you’re baking you’re dealing with chemical reactions,” says Tutor.com chemistry tutor and former
baker Darren L. “If you understand the chemistry, it gives you an edge.”
Here’s a recipe for chocolate chip cookies in chemistry speak.
Ingredients
In Chemistry Speak
¾ cup sugar
Sucrose
¾ cup packed brown sugar
Sucrose and flavoring
1 cup butter
Fat
1 large egg
Albumin, fat and protein
2 ¼ cups all-purpose flour
Gluten
1 teaspoon baking soda
Sodium bicarbonate (NaHCO3) (base)
½ teaspoon salt
NaCl
2 cups semi-sweet chocolate chips
Yummy
Directions
The Chemistry of Baking Cookies
Preheat oven to 375 degrees
Mix sugar, brown sugar,
butter and egg in a large
bowl.
Only physical changes.
Stir in flour, baking soda, and
salt.
You add flour late in the process so that you won’t “work” the dough for too long,
keeping the gluten complexes small.
Stir in chocolate chips.
Yummy!
Drop dough by rounded
tablespoonfuls 2 inches apart
onto cookie sheet.
Size matters. CO2 bubbles form throughout the entire cookie. Only the outside gets
hot enough to caramelize.
Bake 8 to 10 minutes or until
light brown. The centers will
be soft.
When the batter heats up, the sucrose (sugar) breaks down into glucose and
fructose, forming a polymer chain, giving the cookie its light brown, shiny crust.
When sodium bicarbonate (baking soda) heats up, it causes a chemical reaction:
2NaHCO3 ? Na2CO3 + H2O + CO2. The CO2 gas that’s formed makes the
“bubbles” in the cookies. NaCl (salt) keeps the bubbles from getting too big by
slowing the production of CO2. The fat (butter) keeps the flour from forming an
overly extensive network of gluten, giving the cookie a lighter texture. The fat and
protein (egg yolk) hold the dough together and the albumin (egg whites) support the
bubbles.
Let cool for one minute then
remove from cookie sheet
and place on wire rack to
finish cooling.
Cooling allows caramelizing to be completed and allows structure developed by
gluten and egg to set.
http://blog.tutor.com/2010/01/the-chemistry-of-baking-cookies/