Why do we have so many different types of wheat flour?

The full answer to this question really requires us to go back to the beginning and explain where wheat comes from, but I will do that in another post.  For now, let me answer the question about the types of flour and to do that I will just focus on wheat flour.  In our typical grocery stores today, you can find five different types of wheat flour and they are Whole Wheat Flour, Bread Flour, All-purpose Flour, Pastry Flour, and Cake Flour.

If you were to put all five of these flours under a microscope one at a time, you would find something in common with all of them.  They are all mostly made up of the same starch molecules and two specific proteins, Gliadin and Glutenin.  It is not important that you remember the names of the two specific proteins, but that you know there are two specific proteins in the flour and that they are the same two in all of those flours.

For this discussion, let’s focus on the last four flours mentioned above, the bread, all-purpose, pastry, and cake flour.  The main difference between them is how much protein is in each bag of flour.

Bread Flour has between 12 to 13 % protein and 87 to 88 % starch

All-purpose Flour has between 10 to 12 % protein and 88 to 90 % starch

Pastry Flour has between 8 to 10 % protein and 90 to 92 % starch

Cake Flour has between 5 and 8 % protein and 92 to 95 % starch

When you first look at those numbers, the differences between the amount of proteins does not seem like a very big deal.  Let’s leave all those numbers on the sideline for now and focus on what those two specific proteins do in the dough and why it makes a difference. Start by closing your eyes (that is a silly thing to ask because if you close your eyes you will not be able to read this, but you get the picture).  Close your eyes and think about what it was like to bite into a piece of cake.  When you did that you most likely had one chance to bite the cake because there really is not much in a cake to chew on.  Now think about biting into a piece of delicious Italian Bread.  The Italian Bread really gives you something to chew on and it is not just crust.  One of the differences between chewing on cake and chewing on Italian Bread is gluten.  You are really chewing on gluten when you chew on Italian Bread.

So now that we established that gluten gives us something to chew on, where does gluten come from?  Gluten is not in the bag of flour when you open the bag up and it is not in the bowl when you put the flour into the bowl.  The gluten has to be developed by you and that happens when you add a liquid to the bowl and stir the mixture around.  What you are doing when you do that is first you are getting those two proteins wet, that’s the Gliadin and Glutenin Proteins, and when you mix that wet mixture in the bowl, those proteins start bumping into each other.  Glutenin Protein loves Glutenin Proteins and when the ends of those proteins bump into each other and they are wet, they hold on to each other for dear life.  So the more you mix (or knead the dough) the more those proteins find and then hold on to each other.  As more and more Glutenin Proteins string together they start trapping the Gliadin Proteins and before you know it you have what is called a gluten network or just gluten for short.

So if you have more proteins in the bag you will end up with more gluten in the dough.  It is really quite simple.  If Gliadin and Glutenin Proteins are what makes gluten, then if you have more proteins you have to get more gluten.

Now gluten does give you more than something to chew on.  It also makes the dough very extensible and it makes the dough elastic. Extensible is the property that allows you to stretch dough out without tearing the dough (important when you are shaping a pizza or a baguette) and elastic makes the dough pull back when you stretch it (think rubber band).  Now look back at the chart of the flour types above and look at how much of those proteins are in each type of flour.  The numbers or the difference in proteins in each type probably seemed very little when you first read the chart.  Now think about the difference between chewing on cake and chewing on Italian Bread.  Now you should be able to see how important those number differences are to the baker.

As I said gluten does more than give us something to chew on and we will discuss that in another post.  I hope this post gives you a little more understanding of the different wheat flour types.  It is really as simple as, how much gluten do we want in the final product and how much protein will it take to make that gluten.