Cake flour vs All-purpose flour

For those who haven’t really tried their hands on baking or have just started with the craft, all-purpose flour is practically used for everything. Besides, the name suggests it so. Truth is all-purpose flour is just one of the many variations. Another kind would be cake flour, also commonly used in pastry-making. All-purpose and cake flour are both produced from wheat.  However, they differ significantly in terms of the protein it contains, the quality of gluten in the flour, and thus, their suitability in particular pastries. Protein content plays a crucial role in the structure of the finished baked product. It controls the gluten amount that is made while leavening and kneading the flour. Gluten strength indicates the airiness, toughness, and crumbliness of the pastry. The more protein flour contains, the stronger the gluten content, thus the denser and heavier the result.
All-purpose flour, also known as flour particularly in European countries, is made from a combination of hard and soft variants of wheat like winter and red respectively, while cake flour comes purely from soft varieties. Wheat used in all-purpose flour contains higher amounts of starchy portions or endosperms which are more resistant to crushing. Cake flour has less of these portions, thus has a finer texture compared to all-purpose flour. Another reason that contributes to its texture is that it is slightly treated with chlorine dioxide. This, as well, leaves an acidic hint to the end product.
Protein in all-purpose flour ranges from 11% to 12%. This varies depending on geographical location. Case in point, that coming from Southern areas contains less protein than that from the Northwest. Cake flour has lower protein content at 7% to 8%. Consequently, its gluten content is weaker than that of all-purpose flour, making it suitable for lighter, softer cakes.
Baking enthusiasts prefer all-purpose flour in making pastries such as pancakes among many other types of denser products. It makes them fuller and slightly crisp. Cake flour, on the other hand, is better for biscuits, chewy cookies, cake bars, cupcakes, cakes and pastries that should be soft and light.
Both all-purpose and cake flour are commercially available. They’re often found in the baking section of supermarkets, often packaged in a box or in a paper sack.  Martha, King Arthur’s, Cream, Ceresota, Gold Medal White Lily, Hodgson and of course, Pillsbury brand to mention a few. Top cake flour brands would be Pillsbury, Queen Guinevere, Swans, Softasilk.
However different, all-purpose flour and cake flour can be used interchangeably with some recalculations on the recipe. For example, one cup cake flour equals three quarters all purpose flour together with 2 tbsp. cornstarch. Similarly, one cup and one tablespoon of cake flour can make up for a cup of its counterpart.
Summary

1. All-purpose flour and cake flour differ in protein content, the quality of gluten in the flour, and thus, their suitability in particular pastries.
2. All-purpose flour is made using combined soft and hard variations of wheat, while cake flour from soft wheat.
3. All-purpose flour has more protein at 11%-12% than cake flour, which only has 7-8%. Cake flour is ground, thus finer in texture.
4. Denser and heavier pastries like cookies and bread are best made with all-purpose flour. Cake flour is recommended for softer, lighter baked products such as cakes, biscuits and cupcakes.
5. All-purpose and cake flour may be very different but they can be used as a substitute to one another with slight changes in measurements. They are both commercially available in grocery stores.