If you make bread every weekend or have an obsession with cakes, it makes sense to keep specific flours for those recipes on-hand. But what about the rest of us? Is there such a big difference between these flours or can all-purpose flour really be used for all purposes?!
First, what's actually the same about all these flours is that they are made from wheat. What makes them different is how they're milled, what kind of wheat they're made from, and even what time of year the wheat was harvested. But what it really all boils down to is protein content.
Protein content is directly related to how much gluten can be formed using that particular flour. Gluten helps create structure and determine texture in your final baked good. Flours with low protein contents will generate less gluten and flours with high protein content will create more.
To get the light and airy structure of cakes, you want a flour with very little protein. But to form the dense chewy structure of bread, you want a flour with a lot of protein so that you can create as much gluten as possible.
Here is the approximate protein content of all the common types of flour:
Bread Flour: 14 - 16%
All-Purpose (AP) Flour: 10 - 12%
Pastry Flour: 9%
Cake Flour: 7-8%
The exact protein content varies by brand, by region, and also by country. However, the name given to the flour is usually an indication of how it's intended to be used. If you're having trouble with a recipe written by someone in another country, try to figure out the protein content of the flour they're using and then find your local equivalent.
Substituting flours with different protein contents can get a little tricky. For most intents and purposes, you're safe using pastry and cake flour interchangeably. You can also generally use AP flour for either pastry or bread flour.
If all you have is AP flour, you can approximate cake and pastry flour by adding 2 tablespoons of corn starch to a scant cup of AP flour. Likewise, you can bump up a flour's protein content (and it's gluten potential) by adding a few tablespoons of vital wheat gluten.
What flours do you keep stocked in your pantry?
Related: Kitchen Storage: The Best Place to Keep Flour
(Image: Flickr member Mel B. licensed under Creative Commons)
Yuck: A Fourth Grader Reveals What School Lunches Really Look Like
How to Make Fresh Pasta Dough in the Food Processor
Good Food to Share 
The Big Book of Small, Cool Spaces 
Apartment Therapy Presents 
The Eight-Step Home Cure 
Floral Drink Dispen...
Using Luxury Rooms to Keep Teens Home
Juan's Garage Turned Modern Guest House
Thank you, Emma! I've been wondering about "cake flour" for quite a while now.
Just an AP, unless a recipe specifically calls for something different. Good tips here; now I don't have to get the others.
Unbleached AP, bread, semolina, dark rye, whole wheat, white whole wheat, whole wheat pastry, cake, and rice. May be bordering on excessive now that I see it typed out, but I bake a lot of bread and the rice flour is great for coating protiens and for making horchata.
Does "00" flour perform in the same manner as pastry flour?
Yes!!! Thank you so much for answering this!!!
I currently keep AP, bread, cake, whole wheat, and spelt flours in my baking cabinet!
00 flour is actually has a fairly high protein content (11-12%) but is just ground very finely. It's not so ideal for pastry, but is GREAT to use for pasta and pizza crust.
Another bread baker here. My cupboards are stocked with AP, bread, rye, whole-wheat, chickpea, spelt, semolina, and buckwheat flours.
Why is cake flour bleached? Not sure if it is for how the final product looks or it does something for the consistency.
I tend to keep all purpose flour and whole wheat around.
AP
Whole wheat
Semolina
Manioc/tapioca flour
Bread
Rye
Cake
Pastry
I basically have cake and bread flour always on hand because I do a lot of baking.
If the recipe calls for All Purpose, I mix the two together in equal proportion.
Occasionally, I would buy whole wheat if I were actually planning to bake something in particular.
I also keep some rice flour.
Thank you for this! I was hoping to make bread out of my pastry flour tonight but now realize it's not the way to go. ;)
This reminds me of the line in the movie Stranger than Fiction, "I brought you a dozen flours"...
I recently started baking bread using the No-Knead method. I was using AP flour and happy with the results, but the dough didn't seem to be rising like all the pictures and videos had been seeing on the Internet. I recently bought a bag of King Arthur bread flour and the results were astounding. The first rise almost rose right out of the bowl. I am sold. Thank you for this article, it really helped me to understand the differences!