Bake a Different Cake
By Sabrina and Christine
Heat and baking: there are two types of chemical reactions to consider; one is exothermic, and the other is endothermic
Endothermic: a reaction or process which absorbs heat from its surroundings.
Exothermic: a reaction or process which gives off heat to its surroundings.
Baking a cake causes chemical changes.
The baking soda (sodium hydrogen carbonate) becomes sodium carbonate, water, and carbon dioxide, making the cake have little holes in it:
2 NaHCO3 → Na2CO3 + H2O + CO2
When fat and sugar are mixed together – the process is called creaming –
little bubbles of air are being trapped in the mixture, each one surrounded by a film of fat (which is why the mixture changes colour during creaming as the trapped air creates a foam).
It is this air which produces the lightness in the finished cake, but unless beaten egg is added to the mixture the fat would collapse and the air escape during cooking.
The egg white conveniently forms a layer around each air bubble, and as the temperature of the cake rises in the heat of the oven this layer coagulates and forms a rigid wall round each bubble, preventing it from bursting and ruining the texture of the cake.
During the baking:
bubbles of air will expand and the cake will ‘rise’.
At the same time the stretchy gluten in the flour – which has formed an elastic network round the air bubbles – will stretch until, at a higher temperature, it loses its elasticity and the shape of the cake becomes fixed.
Importance of timing the cake:
the expansion process must be allowed to continue uninterrupted. Which is why
a) the cake should be baked as soon as it is mixed
b) even more importantly, the oven door should never be opened in the early stages of cooking: the temperature will drop suddenly and the air in the cake will stop expanding and actually contract. The whole structure of the cake will then sink back because there’s nothing to prop it up.
Cooking oil is a compound of triglyceride and unsaturated acids
The oils serve a number of purposes in this role:
Shortening – to give pastry a crumbly texture.
Texture – oils can serve to make other ingredients stick together less.
Flavor base – oils can also "carry" flavors of other ingredients, since many flavors are present in chemicals that are soluble in oil.
oils can be heated and used to cook other foods.
Oils suitable for this objective must have a high flash point.
Oil makes a cake moist
Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate and a weak acid, and is used for increasing the volume and lightening the texture of baked goods.
Baking powder works by releasing carbon dioxide gas into a batter or dough through an acid-base reaction, causing bubbles in the wet mixture to expand and thus leavening the mixture.
It is used instead of yeast for end-products where fermentation flavors would be undesirable or where the batter lacks the elastic structure to hold gas bubbles for more than a few minutes.
Because carbon dioxide is released at a faster rate through the acid-base reaction than through fermentation, breads made by chemical leavening are called quick breads.
Baking powder is normally made of three different parts:
All three need to be dry powders that can be mixed together.
Structure – Eggs are a big part in the structure of the cake and they give the cake firmness, lightness and stability
Aeration – Beaten eggs include the air into the cake batter
Emulsification – Emulsifiers in eggs bring fats and liquids together into a smooth batter, which makes the cake moist but not greasy
Moisture – Eggs are 75% liquid which can thin out the batter a lot
Fat– Egg yolks have a lot of fat which makes the cake moist and tender
changing the number of eggs in a cake can affect the properties of the cake.
not enough eggs will make a cake that is too compact and falls apart easily.
Too many eggs will make a rubbery cake.
egg volumes can be manipulated to lighten the texture of a cake or add strength to a cake that needs to be carved.
A light, fluffy texture comes from egg whites, and a light quick hand during mixing.
Every ingredient does something.
Flour provides the structure
baking powder and baking soda make the cake airy
eggs bring the ingredients together
oil and butter make it tender; sugar makes it sweet
milk or water gives it moisture.
The proteins in the flour bond and create gluten, making the cake more flexible.
Eggs hold the mixture together.
Baking soda and baking powder both release carbon dioxide, which expands the cake by adding bubbles to the batter.
Each dry ingredient is competing for water.
So you must mix them together in the correct order.
It depends on which ingredient is the strongest competitor.
the water will favor one and be absorbed by a certain dry ingredient that can hold a lot of water.
Putting the wrong one first can cause it to clump because there is not enough water for the rest.
Too much baking powder or baking soda can make the bubbles float to the top and pop. Which sinks the cake. Adding too much also can give it a chemical taste.
100 Index cards
Science journal (optional)
100 small loaf cups
Ingredients for one cake
6 tablespoons flour
3 tablespoons sugar
1 pinch of salt
2 or 3 pinches of baking powder
2 tablespoons milk
2 tablespoons cooking oil
¼ teaspoon vanilla
⅓ of an egg (Break egg into a cup; beat until mixed, then use approximately one third of it. Save the rest for 2 of the other cakes.)
Take out one loaf cup.
Coat the inside of the "pan" with the cooking oil, or cooking spray so the cake doesn't stick.
Preheat the oven to 350 degrees.
Mix all of the dry ingredients together.
Now, add the wet ingredients (as stated in the ingredient list, only use one third of the egg; save the rest for the other cakes).
Stir the wet and dry ingredients until they're smooth and all the same color.
Pour batter into the "pan."
Bake in the oven for 15 minutes.
After 15 minutes, remove the cake from the oven, set aside, and let cool.
Label the first cake “#1 control” on an index card.
Repeat steps 4-10 24 more times.
Next repeat the same steps 25 more times but remove the oil out of the cake. Label these “#1 no oil”
Next repeat the same steps 25 more times but remove the egg out of the cake. Label these “#1 no egg”
The last test will be a cake without baking powder. Repeat the cake making process 25 more times and label these “#1 no baking powder”
After baking, weigh each cake in a small kitchen scale.
Record answers in the science journal
Compare density of the tested cakes to the control group
Record in science fair journal
Data and Tables
Table 1 Graph displaying data collected from each control test cake, including Mass, Volume, and Density.
Figure 1 A bar graph comparing the densities of each cake from Table 1.
The most bubbles formed as the cakes were baking. The average density for the cakes was 0.309.
Table 2 Graph displaying data collected from each test cake without oil, including Mass, Volume, and Density.
Figure 2 A bar graph comparing the densities of each cake from Table 2.
Some bubbles formed as the cakes were baking. The average density for the cakes was 0.367.
Table 3 Graph displaying data collected from each test cake without baking powder, including Mass, Volume, and Density.
Figure 3 A bar graph comparing the densities of each cake from Table 3.
Very few bubbles formed as the cakes were baking. The average density for the cakes was 0.519.
Table 4 Graph displaying data collected from each test cake without eggs, including Mass, Volume, and Density.
Figure 4 A bar graph comparing the densities of each cake from Table 4.
Many bubbles formed as the cakes were baking. The average density for the cakes was 0.378.
volume: 3.4r2 x height
r= radius of cake base
height= in cm
m= mass of cake (g)v= volume of cake (cm3)
There were two possible errors that occurred in the experiment. The first error was that the measurements for each cake where not exact and there could have been an unequal amount of one ingredient in each of the cakes. The second error was that the amount of time each cake got in the oven, then set aside and cooled varied by a few minutes depending on when the cake was measured. These errors could affect the outcome of the experiment by slightly altering each test. In the future, to solve these problems, time will be taken to measure each cakes ingredients exactly to make sure that there is no change in the amount of cake batter put in each cake. Second, there will be a timer for the amount of time each cake gets in the oven, and a timer for how long the cakes are allowed to cool. This will ensure that each cake gets the same baking time and cooling time before they are measured.