This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
To determine the factors that affect the texture of angel cake. Standard recipe:
Egg whites........... 1 cup
Sugar................ 1 1/4 cups
Cream of tartar....... 1 teaspoon
Salt.................. 1/4 teaspoon
Directions for mixing and baking.
Bake 1/6 of the recipe for each experiment. Beat the egg whites until frothy, then add cream of tartar and salt. Continue beating until they are the desired stiffness. The peaks formed when the white follows the lifted beater stand up fairly stiff and the tip end is slightly rounded. Sift the sugar to remove lumps and large crystals so that it will dissolve readily when mixed with the egg white. The sugar is sprinkled over the top of the egg and then folded in with a spatula. See Experiment 67 for directions for folding. The class should use spatulas of the same size. An egg beater can be used to fold in the sugar, but if used all members of the class should use one, and the number of strokes may need to be changed according to the size of the egg beater. The flour is sifted to remove all lumps so that it folds in readily with the mixed whites and sugar. If the sifter is a coarse one, sift the flour several times. The flour is sifted over the eggs, then folded in. Flavoring is omitted in the above recipe so that the flavor of ingredients is more distinct. When used it may be added with the cream of tartar, thus preventing excess folding. To better compare the effect of other factors it is preferable to beat the egg whites together and then divide after they are beaten. Pans 2 1/2 by 2 1/2 by 5 inches will hold 1/6 of the above recipe. It is better to bake the whole recipe in a pan with an opening in the center to facilitate baking, but small portions bake well in a loaf. Let the baked cakes hang inverted in the pans until cool.
A. To determine the amount of mixing of sugar to yield the best texture and volume.
I. Standard method.
Beat enough whites at one time for the whole recipe. Add the cream of tartar and salt. Divide into 6 parts, using 38 grams of the beaten white for each 1/6 of the recipe. Bake at 175°C. (347°F.). There should be several girls in this group. One girl should beat and weigh the egg whites. Each girl should do the same manipulation on each cake. Thus if one girl folds the first 1/4 of the sugar, she should do this operation on each cake, but no more, and pass it on to the next girl. Two girls can fold the flour, the first adding 3/5 and the other the remainder.
1. Add approximately 1/4 of the sugar, sprinkling it over the top of the beaten egg. Fold 5 times with a spatula. Repeat for each 1/4 of the sugar. This gives a total of 20 strokes for folding in all the sugar.
Sift approximately 1/5 of the flour over the egg and sugar mixture. Fold with 5 strokes of spatula. Add another 1/5 of the flour and fold a total of 10 strokes with the spatula. Add 1/5 of the flour and fold a total of 15 strokes. Add 1/5 of the flour and fold a total of 20 strokes. Add the last 1/5 of the flour and fold a total of 40 strokes.
2. Repeat 1 but fold each 1/4 of the sugar 10 times with the spatula.
3. Repeat 1 but fold each 1/4 of the sugar 15 times with the spatula.
4. Repeat A1, but fold each 1/4 of the sugar 20 times.
5. Repeat A1, but fold each 1/4 of the sugar 30 times.
6. Repeat A1, but fold each 1/4 of the sugar 45 times with the spatula. What is the effect on the size of the cells and cell walls when the sugar is sufficiently mixed? When it is over-mixed? When it is insufficiently mixed? Can the flour be blended well if the sugar has not been sufficiently mixed? What is the effect on the texture and tenderness of longer mixing?
II. The meringue method.
Follow the same procedure as for Al, but do not beat the egg whites quite so stiff. The peaks should be soft and the tip end should round over readily. It may be necessary to decrease or increase each of the following parts by 5 or more strokes, depending on the stiffness to which the egg white is beaten. If desired 1/4 of the sugar may be sifted with the flour. Follow directions under AI,1 for folding the flour. Weigh out 38 grams of white for each part.
1. Add 1/4 of the sugar to be beaten in the egg white. Beat the sugar into the egg whites using 10 turns of handle of rotary beater or 10 strokes of whisk for each 1/4 of the sugar.
2. Repeat 1 but use 15 turns of rotary beater handle or 15 strokes of whisk for each 1/4 of the sugar.
3. Repeat 1 but use 20 turns of rotary beater handle or 20 strokes of whisk for each 1/4 of the sugar.
4. Repeat 1 but use 25 turns of rotary beater handle or 25 strokes of whisk for each 1/4 of the sugar.
5. Repeat 1 but use 30 turns of rotary beater handle or 30 strokes of whisk for each 1/4 of the sugar.
6. Repeat 1 but use 35 turns of rotary beater handle or 35 strokes for each 1/4 of the sugar.
Results and conclusions.
B. To determine the amount of mixing of flour to give the best angel cake. Beat enough eggs at one time to make 1/2 of the full recipe. Add cream of tartar and salt for 1/2 the full recipe. Divide the beaten egg white into three parts using 38 grams for each part. Use either the standard or meringue method of adding the sugar, with number of strokes found best under A. Divide the work so that each girl does the same manipulation on each cake.
1. After adding the sugar, add the flour. Fold in with 40 strokes. Follow directions for folding flour under A1,1.
2. Repeat B1, but use 10 strokes to mix each 1/5 of the flour and a total of 60 strokes.
3. Repeat B1, but use 15 strokes to mix each 1/5 of the flour and a total of 80 strokes.
What is the effect on the grain, the volume, and the tenderness of the cake when the flour is mixed too long? Can less than 35 strokes be used?