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Cookie chemistry

This article appeared in the December 23, 2011 edition of the Davis Enterprise.

By Lisa Justice

Special to the Enterprise

Many of us are taking to our kitchens in epic baking efforts this time of year.  But do you know what all those different ingredients in your favorite cookie recipe do for your baked goods?  We put in chocolate chips because they’re tasty, but what’s the cream of tartar for?

Mixing butter and sugar or flour and water together causes some crazy chemistry to happen.  Let’s explore what’s happening to all those food molecules in the mixing bowl and the oven.

Flour is a core ingredient in many baked goods.  Flour contains proteins that react with water to form gluten.  Gluten is like the walls of a house; it provides structure and holds everything up.

You can see gluten at work by slicing into a loaf of bread and observing the air pockets inside.  Notice how the bread molecules around the air pockets weave together.  This is the gluten holding up the crust or roof of the loaf of bread.

Flour is important for creating a framework for our favorite treats, but most of us don’t want our cookies and cakes to be as dense and firm as a loaf of bread.  That’s where fats come in.

We add fats like butter and oil to our baking to help keep the flour under control and prevent it from making too much gluten.  Fats find the protein molecules in the flour and coat their outsides so fewer of them can bond with the water and create gluten.

But what about that cream of tartar?  Cream of tartar is a white powder that is a natural byproduct of winemaking.  Its scientific name is potassium hydrogen tartrate, and it’s an acid that comes from tart fruits.

Bakers add cream of tartar to their cookies to balance out all the chemical reactions happening in their dough.  Cream of tartar can help baking soda release carbon dioxide, helping the dough rise and making the finished product light and fluffy. 

Cream of tartar can also prevent the sugar from forming hard crystals.  This keeps our cookies smooth and creamy instead of too hard and too crunchy.

So as you’re whipping up your seasonal treats, experiment with the chemistry in your oven this year.  Try picking a favorite recipe and make three or four batches of it, but leave out a different ingredient each time.

What happens when there’s no egg or no oil?  What’s it like when you leave out the baking soda?  Can you observe what each individual ingredient does for your cookies?

A good recipe needs all the ingredients to work together to make the chemistry just right and create a delicious treat.  Like us on Facebook to share some of your favorite winter recipes and tell us about how you experiment with chemistry in your kitchen.

Also join us December 24 and December 27-31 from 1:00-5:00pm to explore other science wonders in the world around us with our “Forces of Nature” exhibit.


Explorit’s coming events:

Explorit’s exhibition, “Forces of Nature” is open December 20 – 24 and December 27 – 31, 2011 for the winter break from 1:00 to 5:00 p.m. at 3141 5th Street.


Explorit Science Center is located at 3141 5th St. and is open to the public every first Saturday and Sunday of the month.  For more information call (530) 756-0191 or visit, or “like” us on Facebook at

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