Beating the egg whites to obtain the possible maximum cake volume usually produces the most tender cake, for with a maximum volume the cell walls are stretched to the greatest extent, hence are thinnest.

The method of folding or mixing also affects the grain of the cake. After egg whites are whipped, the folding and mixing should be done gently and to retain as many of the air bubbles as possible.

Longer mixing of the sugar with the egg whites tends to give a finer grain (see Fig. 37), but not to the extent that the folding of the flour does. Thus the grain or texture of the cake may vary to a certain extent, but a cake with thin cell walls and medium-sized cells that is so tender that it "melts in your mouth" is preferable to one that has a fine grain but is less tender.

Ingredients used in angel cake. Flour. The amount of flour per gram of egg white may vary from 0.2 to 0.4 gram. The smaller amount tends to give a more moist and tender cake, the larger a more dry and less tender one. Cake flour produces a more tender cake than bread flour. It contains gluten that is not so tenacious, and therefore yields a cake that is more tender and of greater volume. The cakes made of bread flour shrink and pull away from the pan as they finish baking and while cooling. See Fig. 38, which is a reproduction of the manipulation and proportions for the cakes in Fig. 37. It is possible to obtain a fair cake from bread flour, but it is not as tender as with cake flour. Better results are obtained with bread flour if the sugar is increased by about 2 to 4 tablespoons or the flour reduced by about 2 to 4 tablespoons. There is also a greater tendency for drops of sirup to collect on the surface of the crust when bread flour is used.

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Fig. 41. - Angel cake. Showing effect of increasing the sugar from 1 1/4 to 1 1/2 cups. Typical sugary crust. Experiment (69,F). As shown in the illustration the cakes are about five-sixths actual size.

1. Egg white beaten to flow slowly in a partially inverted bowl.

2. Egg white beaten stiff enough to stay in an inverted bowl.

3. Egg white beaten until very dry and flaky.

Liquid. There does not seem to be any advantage in adding about 30 cc. of water to the egg white.

Cream of tartar. Angel cake made without cream of tartar is cream colored. The cream of tartar produces a very white cake on account of the effect of the acid salt on the flour. The flavone pigments of flour are cream colored when slightly alkaline but white when the reaction is acid or neutral. Also the addition of cream of tartar produces a more tender cake. Evidently the tartrate ion brings about peptization of the egg or flour proteins, or both. Increasing the quantity of cream of tartar beyond the amount used in the recipe produces a more tender cake and one that is more moist and tart in flavor. Barmore recommends that the amount of cream of tartar should be 1 to 2 per cent of the weight of the egg white. The amount given in the standard recipe is about 1.5 per cent.

Sugar. A fine crystalline sugar, such as fruit or berry sugar, which dissolves rapidly is excellent to use in angel cake. The maximum amount of sugar per gram of egg white is about 1 gram. At higher altitudes this must be decreased. At sea level, or up to 1000 feet above sea level, the sugar can be increased to 1.25 grams of sugar per gram of egg white provided the maximum amount of flour is used. But it must be handled carefully. See Fig. 41. Cakes with large proportions of sugar have a typical sugary crust.

Temperature of baking angel cake. Reports of recent investigations of baking temperatures for angel cake indicate that higher temperatures than those commonly used are preferable. Barmore reports that cakes baked at 178°C. (352°F.) had a larger volume, were more tender (probably because of larger volume), and appeared more moist, though a moisture analysis showed no cakes lost moisture farther from the edge than 1 cm. Burke and Niles have reported a larger volume, more tender cakes, and less moisture loss for cakes baked at 350°F. than for those baked at 325 °F. Peet and Lowe have reported a larger volume, more tender cakes, and more moist cakes when the cakes were baked in preheated ovens of electric, gas, and kerosene ranges than from a cold start in these same ranges.

Whether still higher temperatures will be more desirable has not been reported. At present it appears that oven temperatures of 175° to 180°C. are preferable to 150° or 160°C.