Acids and Bases: Cakes

Ladies and gentlemen, children of all ages, step right up and witness the magic!  From the exotic unicorns of Morocco to the hippogriffs of the Himalayas, from the Loch Ness Monster of Scotland to the leviathans of the Grecian oceans, never before has there been something so magical as what I am about to reveal to you.  This miraculous occurrence, this stunning trick of magic, will make your mind spin and delight your senses!

May I present to you...

The baked cake!

Enough with the theatrics, I admit that intro was incredibly corny.  But, seriously, the common cake never ceases to amaze me.  Many would disregard the magical transformation a cake goes through during its life; from dozens of separate ingredient, it becomes a sloppy mess.  That sloppy mess then passes through a magical box in which it morphs into a delicious, light, cohesive cake.  Upon leaving the oven, that previously formless mass has become a beautiful concoction to tantalize the tastebuds.  It's really an amazing process, but the magic is actually just a whole lot of chemistry.

We'll start with the denaturing of proteins.  The egg proteins as well as gluten (a protein in the flour) are developed and denatured.  This means that they rearrange their shape, becoming more stable and giving the cake structure.  Denaturing, or coagulation, can occur via many catalysts, including the use of heat, acids, and physical stress.  In cakes, we generally use the heat option (hence the oven).

While denaturing really is fascinating, the truly amazing part is the lift that occurs in the cake.  A leavening agent is used to create bubbles in the batter, and tiny air pockets result.  These pockets are then locked in place to create a light, tender cake.  The creaming method employs sugar granules to punch tiny holes in the butter, which then expand to create a tender crumb.  However, there are other leavening agents such as baking soda and baking powder that create carbon dioxide bubbles during baking to introduce volume to the cake.  Plain baking soda is just sodium bicarbonate, which needs an acid to produce carbon dioxide.  If an acid is present in a recipe, baking soda is used.  If not, baking powder includes an acid (cream of tartar) in addition to the sodium bicarbonate.  The reaction is as follows:

NaHCO₃ + KHC₄H₄O₆ → KNaC₄H₄O₆ + H₂O + CO₂

This reaction will be the basis of our cake baking.  So here's the recipe!

White Velvet Cake

Ingredients

5 cups all-purpose flour

4 teaspoons baking soda

1 1/2 teaspoons salt

2 cups milk (any kind, higher fat content is best)

2 teaspoons vanilla

3 1/4 cup sugar

2 cups vegetable oil

6 egg whites

2 teaspoons white vinegar

Food coloring of choice

Directions

Preheat oven to 350 degrees.

Sift together flour, baking soda, and salt.  

In a separate bowl, beat together sugar, vanilla, and oil for one minute.  Then add the egg whites and beat for an additional two minutes.  Add vinegar and mix until combined.

Fold dry mixture into the wet ingredients in three additions, alternating with the milk.  Do not overmix but ensure that batter is fully integrated.  Divide the batter into separate bowls, one for each color of food coloring.  

This is where you can get creative!  There are many decorative options, but for each, an 8-inch round should bake for 25-30 minutes in the preheated oven.  A toothpick inserted in the center should come out clean.  

Now on to the fun stuff!  If you would like, pour colors one after another into the center of two 8-inch round cake pans (greased) for a rainbow cake (shown below).

You can then run a knife through the colors for a zebra effect:

Another option is to bake half of the batter into colored cake, reserving the other half and leaving it white.  Then, make the colored cake into cake balls.  Pour the reserved white batter into two greased 8-inch rounds and place cake balls in the batter.