Science of Baking - Cake Baking

This marks my 700th post. I know many other bloggers celebrate the anniversary, mile stones, but not me. When I realized that it is a big one, I thought hard what to post. A dessert recipe perhaps? Then thought against it. There are tons of recipes floating around the internet.  Then I thought about what people look for in my blog. I still don't know the answer to it, but I think many people like the Basics page I have put up. Correct me if I am wrong.

Anyways, I thought why not start this post as a beginning for 'Science of Baking'. If you have a recipe, you have a recipe. You know the science behind something, you have a technique. Technique is what is needed to make recipes, adapt a recipe to suit your taste and be a successful baker.  Understanding how ingredients work together when handled in certain ways and under the heat of the oven is very crucial to any baking. In simple words, every one can paint the wall if they want to. But, unless you know how to do prep work, and how to pick what type of paint, tools you need, you can't really do a nice job.

What is a good cake?
One which is moist, has a very delicate crumb texture and is sweet but not overly sweet like fudge. Some cakes are dense. Some are airy, but all have to be moist. A dry cake is not something anyone wants to eat.When the cake is delicate, it should not be crumbly at the same time. If you have a crumbly cake, that means when you slice it, you get a dessert sand, which again is not very appealing.

Ingredients for a cake -
Flour, Sugar, fat like butter, oil, shortening or margarine, eggs or egg substitutes, leavening agents like baking soda, baking powder, salt, flavorings, liquid like coffee, buttermilk, milk, yogurt etc.

Flour:
Usually the type of flour used in cake baking is all purpose flour or cake flour. Yes, you could replace it with whole wheat pastry flour but let me tell you, it is expensive. If you replace it with whole wheat flour, the cake becomes dense. You could however replace half the flour with whole wheat flour without much difference in texture. There are recipes which do not have flour. But almost all of them have either cocoa to replace part of flour or nut flours to replace flour. Flour is what makes the cake structure. Flour is what holds the sugar, butter and binders so that it is a solid dessert.

Sugar:
Sugar or honey or maple syrup, brown sugar are the sweeteners used in cake. They not only add the sweetness, but also moistness to the end product. Sugar being an emulsifier when creamed with butter can create air pockets which constitute towards spongy texture of the cake.

Butter/Oil/Shortening/Margarine:
Fat is what gives the moistness to the cake along with sugar. A fat free cake will not have a nice texture even when you replaced the fat with applesauce or some other fruit puree. It will be dense. Fat when combined with sugar can hold in air in the form of pockets which makes a cake have a spongy texture. You might ask what happens when you use oil since there is no creaming involved. Those recipes are treated more like muffin or bread recipes where you just mix the dry and wet together. Due to the mixing, it still can make the cake spongy, but a butter cake is definitely more spongier than the oil based cake. Oil based cakes win on one strong point. They are moist. Because when you use oil, it is 100 %  fat. When you use butter, it is only 80 % fat.

Eggs:
Eggs do many things in a cake recipe. They can be binders, they can give the moistness/richness and they can give volume too. There are recipes like sponge cake recipe which have very less butter but many eggs. Most of the cake recipes where there are lot of eggs and less butter is involved, it calls for beating eggs with sugar until double in volume. Eggs give volume also in these cases. Then there are cakes which have only egg whites like angel food cake. Angel food cake is a fat free cake and that probably is the reason for using it as an ingredient in many desserts. Then there are chiffon cake recipes which have very few egg yolks but egg whites do give volume here. I cannot generalize the way egg substitutes work. Most of them are for binding the remaining ingredients except for tofu which adds up to the volume of the cake.

Leavening agents like Baking Soda, Baking Powder:
These are required to make the batter produce carbon dioxide which rise the batter making tiny pockets. And when the batter is cooked, this air is trapped among these pockets giving the spongy texture for the cake. There are recipes which do not have any leavening agents at all. Example is the traditional pound cake. Leavening is done by eggs and the creaming of butter and sugar in such recipes.

Liquids:
These can be to flavor the cake or to act as the acid to react with baking soda. There are recipes which are rich in fat and eggs that do not call for any liquid. Liquid from the eggs is good enough to make the batter for such cakes.

Salt, flavorings:
A pinch of salt brings out the flavors beautifully even in a dessert. Flavorings are well flavorings. Think of them as perfumes.

Mixing:
Mixing the batter to the correct level is very crucial in any cake baking. Creaming butter with sugar is one of the main things in many cake recipes which have butter or margarine or shortening for fat part. Over mixing will create too many air pockets there by spoiling the texture of the cake. This also results in creating a higher dome that will make shorter cake when you tort. Under mixing will make the cake dense. In my experience, it is hard to under mix than over mixing. Make sure you don't over mix than what is needed. Over mixing will also make the gluten in the flour to develop which can make the end product hard. Whenever you are dealing with oil or liquid fat, it is very important to fold the dry ingredients instead of beating with the electric mixer. This makes sure there is no gluten development.

How does the cake baking work:
You make the batter which is a thick liquid, pour it into the cake pan and place in the preheated oven. After the baking time, you have  a solid cake. How does that happen? You either fill either half full or 2/3 full. But the resulting product is a full height cake with a dome (unless you used bake even strips). Half of the end product is air. Air trapped between the flour, sugar, fat makes the batter rise. Batter stops to rise once it is cooked. That is the reason for getting the dome. Batter cooks first on the bottom and sides where it is touching the pan sides that transfer heat faster. So, they stop rising at certain point, whereas the middle batter cooks slowly and rises more creating a dome. That is the same reason for the thick crust on the bottom and sides of the cake. When you use bake even strips, you are trying to slow down the cooking of the batter at the edges so it rises evenly. And that is the reason for checking the doneness of the cake by inserting a toothpick in the center and not at the edge. If the center is cooked, the whole thing is cooked.

General formula for a cake:
If you are a cake baking enthusiast, you should read the 'Cake Bible' from Rose. She explains this part so well. I am not going by any particular recipe, but a general thumb rule. Remember there are tons of recipes which adhere to this and there are even more which do not.
Usually for every cup of flour, there will be 2/3 cup of sugar, 1/3 cup of fat, 1/4 cup of egg (or 1 large)  in most of the cake recipes. Leavening agent will be around  1 1/2 tsp baking powder for every cup of flour. If the recipe calls for baking soda, it will be closer to 3/4 tsp per 2 cups of flour. Remember that baking soda is much stronger than baking powder. Each tsp of baking powder has 1/4 tsp baking soda, 1/4 tsp cream of tartar and 1/2 tsp corn starch. Depending on how thick the mixture of fat, flour, sugar make, there is addition of milk or other kinds of liquid to get the batter consistency. Leavening agents need liquid to work. That usually varies from one recipe to other and constitutes for thin batter or thick batter.

Please remember that it is just a guideline and there are too many recipes that do not stick to this rule. Particularly eggless cakes and vegan cakes have an entirely different way of working that is hard to generalize. You can look at various cake recipes on this blog here.

Coming to the interesting part - Did you like this post? Do you think it is a good idea for me to write about Science of baking of various other baked goodies? Or you would just like a recipe and not bother with how it works? Let me know.

Enjoy.