Denatured Proteins: The Structure of Cakes

A cake begins its life as a formless mass of batter.  After entering the oven, a miracle occurs as the glob rises and solidifies into a light but substantive slab.  This is made possible by the denaturing of proteins.

Proteins are strands of amino acids synthesized into a scrambled up mess.  When these proteins are denatured, by heat, acid, or simply disruption (such as whipping), they are pulled out of these bunches and into a more structured form.  This is what gives cakes their shape and holds them together.  This is why eggs are necessary.  

To make this amazing piñata cake, we needed a very structured cake to support the opening within.  Thus, we used a cake recipe with six eggs.  So much denaturing.  So much structure.  

The cake recipe can be found at http://allrecipes.com/recipe/six-egg-pound-cake/
It was a tasty cake recipe.

We made two 9x13 inch pans, cut both into the same shape, and made an indent in each.  Then we lined up the indents, filled them with Sixlets, and stacked the cake.

We decorated the cake with chocolate frosting (the same fudge recipe we used for the Cow Cake) and topped it with the rest of the Sixlets.  Delish.

Crystallization: Fudge

We briefly touched on crystallization in a previous post, but today we actually addressed them in cooking.  Crystallization is a process in which atoms arrange themselves in a fixed ratio with set bonding patterns.  This can be either helpful or harmful in the cooking process; it is necessary for the creation of lollipops, hard candies, and a number of other confections, but very inconvenient when making chocolate fudge.  The creamy, smooth texture of fudge should not be marred by crystals.

So what exactly is crystallization, and how does it affect the foods we eat?  According the dictionary.com, a crystal is a piece of a homogeneous solid substance having a naturally geometrically regular form with symmetrically arranged plane faces.  Chemically, this geometric form is the set bonding pattern of the atoms.  Crystals can be made from ionically bonded atoms (between a metal and a nonmetal), and they can also be an arrangement of molecules (which are compounds of covalently bonded atoms).  

In the case of fudge, the sugar would be the crystallization culprit.  Amidst the silky goodness of the chocolate, small bits of sugar have the potential to attach to one another, forming larger, palpable crystals that mar the fudge.  To avoid this, certain tactics can be employed.  First, avoid introducing any seed crystals into the mixture.  Seed crystals, bits of already crystallized sugar, provide opportunities for other sugar molecules to attach into larger formations.  In addition, adding another substance to block the sugar molecules from connecting will almost guarantee a smooth consistency.  These anti-crystallization agents include honey and corn syrup.  In our fudge frosting, we utilized corn syrup.  

The fudge frosting was poured over a chocolate cake, ringed with KitKats, and decorated with two cows.  The result was an adorable pasture cake. 

We used Ina Garten's Beatty's Chocolate Cake Recipe:

Ingredients
Butter, for greasing the pans1 3/4 cups all-purpose flour, plus more for pans2 cups sugar3/4 cups good cocoa powder2 teaspoons baking soda1 teaspoon baking powder1 teaspoon kosher salt1 cup buttermilk, shaken1/2 cup vegetable oil2 extra-large eggs, at room temperature1 teaspoon pure vanilla extract1 cup freshly brewed hot coffeeChocolate Buttercream, recipe followsDirectionsPreheat the oven to 350 degrees F. Butter two 8-inch x 2-inch round cake pans. Line with parchment paper, then butter and flour the pans.
Sift the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with a paddle attachment and mix on low speed until combined. In another bowl, combine the buttermilk, oil, eggs, and vanilla. With the mixer on low speed, slowly add the wet ingredients to the dry. With mixer still on low, add the coffee and stir just to combine, scraping the bottom of the bowl with a rubber spatula. Pour the batter into the prepared pans and bake for 35 to 40 minutes, until a cake tester comes out clean. Cool in the pans for 30 minutes, then turn them out onto a cooling rack and cool completely.
Place 1 layer, flat side up, on a flat plate or cake pedestal. With a knife or offset spatula, spread the top with frosting. Place the second layer on top, rounded side up, and spread the frosting evenly on the top and sides of the cake.

This is the fudge frosting recipe:
Place 1 cup granulated sugar, 1/2 cup baking cocoa, 1/2 cup milk, 1/4 cup butter, and 2 tablespoons corn syrup in a saucepan.  Bring to a boil, stirring constantly.  Remove from heat, place in an ice bath, and whip until cool.  Add 1 1/2 cups powdered sugar and whip until smooth.  Apply to your favorite cake. 

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. 

Aromatics and Ring Structures: Caramel

Caramel is made from sugar, but though the basic elements are the same in each substance, the flavor, texture, and smells of each are entirely unique.  This is because regular sugar, or sucrose, must undergo a chemical reaction before it becomes the gooey goodness we call caramel.

Now, before we continue, a quick word about chemical reactions... they only occur when bonds are broken or made.  There is a difference between physical and chemical changes: chemical changes restructure the configuration of atoms while physical changes do not.  For example, dissolving sugar in water only disperses the same molecules in water, it does not change the molecules themselves.  However, caramelizing sugar rearranges the molecules and breaks them down, forming new molecules.  The reaction is as follows complicated but involves the sucrose molecules breaking down into fructose and glucose, and eventually forming into new rings and aromatics.  This all occurs with the addition of heat, and it is a temperamental process.

Here is a pictoral representation of the carbon rings in both sugar...









and caramel...

To make caramel, recipes begin with either the wet method (combining sugar, water and a crystal inhibitor and then boiling) or the dry method (melting dry sugar and then adding other ingredients).  I prefer the more testy dry method because it is easier to gauge doneness and draw out a real caramelized flavor, but the wet method is often 'safer' in that it leaves less room for error.  We will focus on the dry method for the sake of its obvious chemical transformation.

To start, place the sugar and water in a large saucepan and begin heating, stirring occasionally.  After some time it is evident that the sugar is melting (caramelizing), shown by the sticky residue that coats the bottom of the pan.  Though it may take a while, let the caramel cook until it is a uniform, thick, smooth amber color.  At this point, the chemical reaction has occurred, and the aromatic rings should be tantalizing your nose with nutty--but not burnt!-- caramel smells.  Now the going gets tough.

After caramelization, crystallization becomes the primary issue.  This is when sugar crystals begin to form in the caramel, creating a grainy texture.  To avoid this, don't allow any "seed crystals" of sugar into the caramel.  Seed crystals are pieces of sugar that would provide opportunities for other sugar molecules to latch on, ruining the silky caramel goodness.  Adding an anti-crystallization agent, such as honey or corn syrup, interferes with these molecules latching on to one another and thus helps as well.  We used honey in our caramel.  It also added a dimension of flavor.

When the caramelized sugar is prepared, add in the butter and other ingredients, stirring constantly.  The caramel may seize for a minute, but continued stirring will smooth things out.  At this point, the mixture should be stirred as it cools to keep it uniform and delicious.  Whisking it while submerged in an ice bath works marvelously.

We put our caramel on the top of some brownie batter and baked up some salted caramel pretzel brownies.  MMMMMMMMMMMMMMM...

Colloids: Gels

Similar to our previously mentioned foams, the gels we made today are a type of colloid.  They occur when a solid is dispersed within a liquid.  We used gelatin as our basic gelling agent, a tricky convenience because gelatin is lyophilic.  This means it can be made easily by simply warming the substances, so we could use the same base and ingredients to make multiple different types of gels.  Adding differing amounts of gelatin was what allowed us to make different textured gels- candy-like gummies, jelly, and a jell-o somewhere in between the two.

We began by making a fruit base as the flavoring for our gels.  We blended up some berries, sugar, juice, and corn syrup to make a deliciously sweet concoction.

We then separated the syrupy flavoring into three 1/3 cup measures, one for each type of gel we intended to make.  Each was heated to a boil, at which point the corresponding amount of gelatin was added.  Incidentally, the gelatin had to be sprinkled evenly over the hot liquid to avoid clumps of unflavored gelatin granules in the final product.

A brief explanation of what happened at this point of the cooking process: The gelatin began at room temperature, organized into a structure by intermolecular forces.  Upon heating, these forces were broken, allowing the gelatin to take in the water molecules.  As the gels cooled, the intermolecular forces were reinstated, but this time with the water molecules interspersed evenly.

We let the gels cool until they had reached room temperature, and the consistency we were searching for.  In the end, we had fruit gummies, fruit jelly, and real fruit jell-o.  So many gels, so little time...