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Function of Flour in Baking

If there is one ingredient that defines baking, I would argue that it is flour. Specifically, wheat flour. Sure, sugar is important for desserts and pastries, but flour is the backbone of most baked goods.

a photos of different types of flour

Composition of Wheat Flour

Wheat flour is composed of proteins, starch, lipids, sugars and enzymes. The two most important of these components, the starch and the protein, form the “crumb” of a baked good. The crumb is a network of starch and protein interspersed with millions of tiny air bubbles.

Wheat flour is about 70% starch. Starch granules absorb water from the batter, swell up, and gel. As an item bakes, the gelled starch sets to help form the physical structure of the baked good.

Protein is the other major component of wheat flour. When a batter or dough is mixed, two proteins in the dry flour, glutenin and gliadin, absorb water and form gluten.

Gluten is a network of coiled and folded protein strands. The stronger the gluten, the more water it will absorb.

If you replace a low protein flour with an equal volume of high protein flour the batter will be much thicker, since the stronger gluten will absorb more of the available water.

Using a higher protein flour changes the outcome of the recipe not only because the gluten is tougher, but also because there is less water available to the other ingredients in the batter or dough.

three portions of flour mixed with water

The stronger the flour protein the more water it will absorb.

Why We Knead Dough:

As a batter or dough is mixed or kneaded the coiled and folded strands of gluten begin to align and tighten.

This is why a bread dough that starts out loose and “shaggy” becomes smooth and silky as it is kneaded. This is also why over-mixing batter will give you tough pancakes or a dense cake.

Types of Wheat Flour:

Hard wheat (often a “spring” wheat) is high in protein and low in starch. When this high protein wheat is milled, the hard kernels break into large chunks that will form a strong gluten network when they come in contact with water.

Soft wheat (often a “winter” wheat) has a lower protein content and higher starch content. When low protein wheat is milled, the soft kernels break into very fine particles. Winter wheat produces a fine and silky flour that forms a weak gluten network when it comes in contact with water.

Bread flour contains more of the high protein wheat and cake flour contains more of the low protein wheat.

All purpose flour is a mix of both types of wheat and has a medium protein content.

Whole wheat flour is similar in protein content to all-purpose flour, but the bran and germ are left in the flour.

An equal volume of two different flours may not be equal by weight. For example, one cup of cake flour weighs about 4.5 oz and 1 cup of bread flour weighs about 5 oz (using the “dip and sweep” method).

Those differences are important to remember if you switch out one type of flour for another in a recipe that uses volume measurement rather than weight measurement.

The Protein Content and Weight Varies by Type of Flour:

Cake Flour is 7-8% protein and 1 cup weighs 4.5 oz

Bleached All Purpose Flour is 9.5-12% protein and 1 cup weighs 5 oz

Unbleached All Purpose Flour is 11-12% protein and 1 cup weighs 5 oz

Bread Flour is 12-13% protein and and 1 cup weighs 5 oz

Whole Wheat Flour is 11-15% protein and and 1 cup weighs 5 oz

If you learn only one thing from this class I hope it is this; bread flour, cake flour and all purpose flour are not interchangeable!

Use bread flour when you want a tight and chewy crumb (bread or pizza!).

Use cake flour when you want a soft and tender crumb (pound cake!).  

Use all purpose flour when you want an in-between texture (muffins or cookies!).

What about Gluten-Free Flour?

Gluten-free recipes use non-wheat flours that don’t contain gluten. When using gluten-free flour, a binding agent must be added to the batter to replace the elasticity lost without the presence of the wheat flour protein.

I have used a commercial gluten-free flour which contains rice flour, potato starch, pea fiber, tapioca starch and xanthan gum. The xanthan gum acts as a binder to replace the structure provided by wheat gluten. 

Without gluten the structure is weaker so a gluten-free baked good usually won’t rise as high as one made with wheat flour.

two Pound cakes made with gluten free flour

Cakes made with Gluten-Free flour but different ways of mixing.

If you can’t eat gluten but love cake, you’ll find a great recipe for Improved Gluten Free Pound cake in my ebook Pound Cake Perfection.

You might also like these other Baking Science Classes:
The same pound cake recipe made with 5 different flours

Flour in Cake Batter

The same exact amount of baking powder mixed in differently affect the cake texture.

Chemical Leaveners

Butter, shortening and oil can all be used in cake batter

Baking Ingredients-Fats

pound cake made with various amounts of sugar

Baking Ingredient-Eggs

The size and shape of salt crystals varies quite a bit

Baking Ingredients-Salt

sugar in baking

Baking Ingredients- Sugar

Tania Summers

Tuesday 9th of August 2022

Thank you so much for this plethora of information! I do have a few simple questions. 1. If I want to make a white cake, instead of using the yolks for the emulsifying agent, can I use high ratio shortening? If so, how much would I use in place of the yolks, in a single recipe? 2. Can I quadruple this recipe and expect the same results! 3. Does this recipe work for cupcakes, as well?

Eileen Gray

Tuesday 9th of August 2022

1. Here's a recipe for white cake. The post has information about how I adapted a vanilla cake recipe to make a white cake. 2. Which recipe do you want to quadruple? 3. Which recipe?


Monday 20th of June 2022

Hi Eileen In this post you show a picture of two Gluten free cakes with different mixing techniques. Which technique results in the higher rise? I seem to be having a lot of trouble getting my Gluten free cake to rise, despite reducing the sugar so perhaps it is the mixing technique? I’d love your thoughts/advice! Thanks!!

Eileen Gray

Tuesday 21st of June 2022

Normally I prefer to use the reverse creaming method to mix cake batter because less gluten formation means a more tender cake. Since that's not a problem in a gluten free cake I found that the traditional creaming method worked better with gluten free flour to get a slightly lighter crumb. But I am by no means a gluten free expert.


Wednesday 8th of April 2020

Just wondering why you’re getting 5oz per cup for bread flour, which is a little more than 140gm. My reference is 120gm per cup.

Eileen Gray

Wednesday 8th of April 2020

Hi David, To measure a cup of flour I use the "dip and sweep" method. That means, I dip the cup into the flour bin, then sweep away the excess. I always get 5 oz of flour this way. If you use the method where you spoon the flour into the cup you can get less weight since there will more more air incorporated during the scooping process. The flour is "fluffier". As long as you're aware of the recipe writer's method of volume measure you can adapt to that or, even better, use weight measure. This is exactly why most bakers will tell you that weight measure is the most accurate. Because there can be variation on how someone does volume measure.


Wednesday 3rd of May 2017

Oh. you just blew my mind up -.- Now I have to do my research on local flours if I can find something similar to cake flour. (I guess I won't find any)


Monday 23rd of August 2021

@Eileen Gray, I'm curious why you didn't tell her how to substitute with cornstarch? Remove 2T./1 cup of AP flour and replace with cornstarch and the formation of the gluten is somewhat inhibited. The rest of your information is spot on.

Eileen Gray

Wednesday 3rd of May 2017

Thanks, Xelita. Good luck with your research.

Lauri M.

Friday 31st of March 2017

I wish to make scones, can I use gluten free flour without adding anything else to the recipe?

Eileen Gray

Friday 31st of March 2017

Hi Lauri. I haven't tried making my scones recipe with gluten free flour. I imagine they'll bake up flatter than usual and will probably spread a bit. You'd have to play with the recipe a little to get it to work. Using gluten free flour I double you'll be able to cut scones like a biscuit and have them rise up straight. I looked the the King Arthur flour website and they have a recipe for gluten free scones that uses gluten free flour plus extra xanthan gum. Good luck.