Non-organic cake flours are bleached.
Very helpful article on cake flour. If you’re an enthusiastic baker (just like Nanna!), then organic flour is most definitely the way to go. It makes all those treats healthier and tastier! – 

Non-organic cake flours are bleached in order to create the higher acid level necessary to achieve the texture and consistency found in cakes. Since organic flours are unbleached, this lack of bleaching will mean a denser and heavier cake than a bleached flour one. 

You might not be aware that cake flour is different from other flours such as all purpose or self rising. A cake flour has a higher starch to gluten ratio which is the reason the cake texture is fine and crumbly.

Cake flour is made from a soft wheat because once baked, it creates a fine crumbly texture, which is very desirable in cakes. This happens because soft wheat flour has a naturally higher starch, lower protein content than other wheat flours. Because of the high starch content, cake flour accepts a higher sugar to flour ratio. This high starch content means there’s less likelihood that once the cake rises; it’ll fall. This is a common problem when using a non-cake flour like an all purpose one. Another valuable quality of cake flour is its ability to maintain a fine texture when baking higher volume foods like breads. That’s why many recipes for quick breads call for you to use cake flour. Cake flour is also an excellent choice for baking muffins and even some cookies because it’ll give added taste and a finer texture.

You can make organic unbleached flour lighter in texture and more suitable for baking cakes by using a simple technique. Just add one tablespoon of cornstarch to each measured cup of flour your recipe calls for. Make sure that the cornstarch is organic, however, because conventional cornstarch generally contains GMOs (Genetically Modified Organisms).

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