Cake flour, all purpose flour and bread flour are the three types of flour that you’ll most often see when reading through recipes. Once in a while, you might notice a wild card and see that a recipe calls for pastry flour, instead. Pastry flour is a high-starch and low-protein flour. It falls somewhere between the (average) 8% protein content of cake flour and the 10-11% protein content of all purpose flour. This means that it is similar to, but not the same as, cake flour. It is often used in pastry and other baking applications where a very tender finished product is desired, as low protein flours will develop less gluten when worked. If you don’t have pastry flour, you can easily make pastry flour by mixing half cake flour and half all purpose flour in a recipe. It shouldn’t be directly substituted for or with cake flour (lower protein, less gluten) or all purpose flour (higher protein, more gluten), as it will change the texture of your finished product. It isn’t always carried by every grocery store, but you can usually find it in the baking aisle of a specialty grocery store that carries a wider range of products and it can be ordered online, as well.
Whole wheat pastry flour is a low-protein flour that is made from whole grains. Many cookbooks that focus on whole grains encourage bakers to use this type of flour because it is much softer and more finely-textured than regular whole wheat flour, and baked goods made with it will have a similar consistency to those made with regular white flour. A good substitution in this case is to mix half all purpose flour with half whole wheat flour in your recipe.