Real Baking with Rose Levy Beranbaum

Bleaching flour is a chemical process that accelerates the natural processes of aging. The oxidation of carotenoid pigments in the flour, which turns the flour from ivory to white, is one of the effects. More significant, however, is that the resulting alteration of the protein molecules effectively denatures their gluten-forming capability and, together with changes to the surface of the starch granules, promotes gelatinization of the starch during baking. This is important because the ability of the flour to gelatinize is critical to the ultimate texture of the cake.

The effects of aging on flour can also be accelerated by physical rather than chemical means. Since chemical reactions are affected by temperature, an alternative treatment to bleaching is controlled heating of the flour. A heat-treated flour can then be used as a viable substitute for chlorinated flour.

A simple form of heat treatment can be achieved in the home by using a microwave. The aim is to heat the flour until it reaches a temperature that is high enough to affect sufficiently the protein, starch, and subsequent gelatinization potential of the flour. Kate has found that the best results are obtained when the flour is heated to 130ºC/266ºF. This heat-treated or “Kate Flour” can be used in recipes that call for bleached all-purpose flour, or it can be mixed with corn flour/cornstarch at a ratio of seven to one to lower the overall protein content of the flour to that of cake flour.

You will need to experiment with the flours available to you. As a general guideline for making cake flour, try to find a finely milled flour with a low amount of protein per one hundred grams. However, a higher protein flour milled predominantly from soft wheats is preferable to a lower-protein flour milled from a mixture of hard and soft wheats. Similarly, a higher-protein flour that is finely milled tends to give better results than a lower-protein but more coarsely milled flour. A paler, whiter flour is also likely to be preferable to one that is darker because light coloring signifies the lower ash content typical of soft flours. Kate has achieved the best results with Italian 00 grade flour, a flour that is finely milled from soft wheats.

The following simple procedure can be used to metamorphose unbleached flour into Kate Flour:

• Weigh out 280 grams/10 ounces of the flour called for and place it on a microwavable plate (the flour gets very hot, so for safety’s sake it is best not to attempt to microwave more flour than this at one time).

• Spread out the flour on the plate to have a bed of 18 to 20 millimeters/¾ inch deep.

• Microwave the flour on high power for about 10 minutes, making sure to stir every 10 seconds to equalize the temperature and prevent browning. After the first 3 minutes check the temperature with an instant read thermometer. Break up any lumps with a fork and continue microwaving and stirring every 10 seconds until the thermometer registers at least 130º C/266ºF. (It is difficult to predict the overall microwaving times as these vary greatly depending on the power of your microwave and the type of flour you are using. However, Kate found that flours needed to be treated for between 10 and 13 minutes on average when using a microwave power of 750 to 800 watts.)

• Allow the flour to cool to room temperature. Sift it and discard any residue.

• If desired, for a slightly higher rise and softer texture, add 1/4 teaspoon xanthan gum and whisk it in to incorporate it evenly.

• If you live in a dry environment, to restore moisture removed during the heat treatment, return the flour to the microwave, or place it in an enclosed container, and set a 1 quart bowl of hot water next to it. Let it sit for 5 minutes, change the water and let it sit for another 5 minutes.

• Make more batches as needed. This flour can be used in recipes calling for bleached all-purpose flour (averaging 11 percent protein).

• To lower the protein content of the flour in order to use it as cake flour (assuming you are using flour with a 9 percent or higher protein content), substitute 2 tablespoons per cup of this flour with 2 tablespoons of corn flour or cornstarch. The most accurate way to do this is by weight. Remove one-eighth of this weight and replace it with an equal weight of corn flour or cornstarch. Place both parts of the Kate Flour in a large bowl and whisk to combine thoroughly.

It is important to note that the amount of corn flour or cornstarch can be adjusted depending on the protein content of the flour you are using and the degree of tenderness you desire in the cake. Lower protein results in more tenderness. Too low a protein content and the cake will dip in the center; too high, and the cake will dome.