Custom baking: what ingredients do in a cake

There's chance that these guys will rise

Do you ever wonder how things work? How come a CRT screen while showing black is still emitting light? Why does it make sound when I crack my knuckles? What is yawning all about? What does milk do in a cake and why does it take a whole cube of butter to make the battenberg cake?

We don't live in the ol' days of analog knowledge where you either had to pick up a huge book and (gasp!) flip pages until you found the answer, or ask your grandma (because they sure know a lot). Anything you want to know is just a Google search away. I've recently pondered, as I closed door to the oven and saw an unopened bottle of milk and remembered that I forgot to add it to the batter, what is milk good for in a cake anyway? The batter was gooey enough and the cake turned out alright in the end, only perhaps a bit too crumbly.

All the confused thoughts spun around my head until I've decided to fight the doubt and search for the answers.

Did you know that there are practically two kinds of ingredients? They either act as strengtheners or tenderizers. It should come as no surprise that the desired texture is achieved by a correct balancing of these two.

Strengtheners are such ingredients that make the cake heavier, firmer, heftier. They include flour, eggs (whole or whites only), milk, salts and acids (except for sour milk and vinegar)

Flour is responsible for providing the cake batter with proteins that when mixed with moisture form gluten - elastic chains of protein that get firm when dry. The amount of glutenin (the protien that forms gluten) is different in different kinds of flours which is why we use different flours for bread (more glutenin), cakes (less glutenin) and cookies (even less glutenin).

too much milk perhaps? depends on what'cha making

Egg whites contain proteins too. Not only they act as a glue of sorts that holds everything together, but the proteins in them when heated expand dramatically and force the water out, thus using too many eggs may lead to the cake being dry.

Liquids like milk and water provide the needed moistness for the protein chains formation but they also improve the texture of the baked result. Proteins in the milk add the nutrition and flavour to the cake and help it brown as well. Water (which is of course in milk too) transforms into steam due to the high temperature in the oven and forms the bubbles in the batter which in turn help the batter to rise and make the cake lighter. 

Fruit juice belongs here too although other acidic ingredients like vinegar and sour milk are categorized as tenderizers. Acids are used in some recipes but shouldn't be used with milk (because acidic and alkaline don't mix well) and due to their nature they are recommended to use with baking soda. The reason for it is that baking soda is pure sodium bicarbonate and reacts (rises) best with acidic ingredients.
Salt belongs even in the sweet cakes and cookies as it brings up other flavours and balances the sweetness. Just don't overdo it.

Tenderizers are the other kind. They soften the cake, weaken the chemical bonds and keep the baked goods soft, moist and, if you put too much of them in, greasy. Not having to take a wild guess, it's easy to see that fat - butter, oil or margarine - belong here, as does sugar, egg yolks (fat again), acids and leaveners.
Crystalline sugar sweetens the cake of course but it also steals water that flour would use and thus prevents the bonds from forming as much. Other favourite sweeteners, honey (did you notice it is sweeter than sugar?) and maple syrup (which is awesomely soft and has a distinct flavour) don't work as well as dry sugar. Crystalline sugar caramelizes in heat and, aside from sweetening it, gives the cake a tint and aroma. Also, sugar mixed with butter allows for little bubbles of air to be incorporated into the batter and act as a sort of a leavener.

deus ex fornax

Fats coat the flour particles and don't let water to form the protein chains. This prevents the result from being all chewy like let's say bread - that's why you put a lot of butter and sugar into muffins to make them so wonderfully delicate. The different kinds of fat give the cake various textures and even flavours. Butter gives the yummy flavour and aroma to any kind of baked goods, margarine don't taste not even nearly the same. Oils also don't work as well as butter - they don't cream with the sugar at all, though they do coat the particles to waterproof them in a similar way. Finally, egg yolks contribute to the flavour, texture and colour of the cake.
Baking soda and baking powder are responsible for the rising of the batter. Other leaveners include air (for example in whipped egg whites), steam and yeast. Baking soda reacts with acidic liquids and immediately starts producing bubbles of carbon dioxide which puffs the batter up. You need to work with it and get it in the oven quickly or the reaction will be over and your cake will fall flat. Baking powder is part sodium bicarbonate but it also contains an acidifying agent (cream of tartar) and a drying agent (starch most commonly). This means that while there is an immediate chemical reaction when in comes in contact with acidic liquid, the major rising chemical reaction arrives when the batter is exposed to high temperature in the oven.

After my research I felt like I've learned something. Now the magic behind making a cake feels a bit more like science, something understandable and fun. Now I guess the only thing to do is to ask my grandma how the hell did she learn all this.

Peace out!