Unbleached Cake Flour

Last week’s Cooking Tip was all about the differences between Bleached and Unbleached all-purpose flour. In this week’s Tip, I want to discuss the same topic but as it relates to cake flour.

Cake flour is a fine-textured flour made from soft wheat. It has a very low protein content, usually around 7-8% as opposed to 10-12% for all-purpose flour. There is also something called pastry flour. It also made from soft wheat but has a protein content just above that of cake flour – about 8-9%.

Since cakes are meant to be tender, you want to reduce the gluten content. This is the purpose of the low-protein cake flour. Almost all cake flours are bleached with chlorine & bromated. (For a review of this topic as it relates to AP flour, see last week’s Tip.) Cook’s Illustrated’s science editor explains that “this process damages the starch molecules and allows for greater absorption of moisture and fat by the flour, which in turn results in moister, more tender baked goods.”

Recently, though, some manufacturers have begun to offer unbleached cake flour. A major player in this market is King Arthur Flour. This product supposedly simulates this moisture attraction without any chemicals. There were two other companies offering unbleached cake flour: Hodgson Mill and Bob’s Red Mill. Since writing this, the former company was sold and I know longer see this product as available. The latter recently discontinued their unbleached cake flour. (They do continue to carry unbleached pastry flours and they recommend their Unbleached White Fine Pastry Flour as a substitute.) I will still mention it below as it was the flour that was tested by one expert.

When Cook’s Illustrated tested the King Arthur product, they found it performed just as well as bleached cake flour. Stella Parks of Serious Eats had a differing viewpoint. In this article, she lists a number of advantages of bleached (chlorinated) cake flour. Note, though, that her testing was only with angel food cake.

She states that the bleached cake flour is not only whiter in color but is also “conditioned”. The chlorine slows the rate of starch gelatinization in flour, thus improving gas retention. This results in a higher rise. It also raises the temperature of protein denaturation, once again giving the cake more time to rise. Additionally, it lowers the pH of cake flour from an average of 5.9 to about 4.8. The lower pH inhibits browning, an aspect that is great for an angel food cake.

When testing the unbleached cake flour, she found that the batter soaked up excess moisture and set too quickly. This inhibited the rise of the cake. Again, the discussion was only about angel food’s cake.

The Cake Blog did a testing of 6 different flours in making a traditional (not angel food) cake. This tester had a very positive view of the unbleached cake flours. A short summary of the results is shown in the following chart.

Type of FlourHeight of cakeTextureColorFlavor
Unbleached AP flourShortestCoarseDeep ivoryWheaty
Unbleached pastry flourModerateMildly coarsePale ivoryMildly sweet
King Arthur unbleached cake flourMediumMed-fine crumbMediumMildly sweet
Bob’s Red Mill unbleached cake flourMedium-tallFine crumbPaleMildly sweet
Softasilk bleached cake flourTallestFine crumbPaleMildly sweet

I must add one caution for those of us at high altitude. Baking cakes at higher altitude can certainly be a challenge. I have written a Cooking Tip on this problem. Using cake flour with its lower protein content may hamper getting good results at altitude. Some experts recommend staying totally away from cake flour. Others will use a mixture of cake flour & AP flour. Some recommend using half & half while others recommend 1/3 cake flour and 2/3 AP flour.

What to make of all this? If you want a great angel food cake, I would probably recommend going with a good bleached cake flour. If not, give one of the unbleached cake flours a try. Let me know what you think.