This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
(2) Time. This factor as in other reactions is also important, the length of time the batter containing soda stands before baking influencing the color obtained. It has been found that cake batter which has stood 10 to 15 minutes - some cake bakers often permit it to stand while they bake a test cake - usually gives a richer mahogany shade than a portion of the same batter baked immediately after mixing. These results have not always been consistent with different varieties of chocolate and cocoa, but are obtained in a majority of the experiments.
(3) The quantity of chocolate or cocoa used. The shade is darker with a larger quantity.
(4) The brand of chocolate or cocoa used. The reasons for variation in color with different brands of chocolate and cocoa have been indicated under their production. There is also a difference in the flavor of different brands of chocolate and cocoa.
(5) The kind of baking powder used. It was quite a surprise to find that, when butter, sugar, eggs, and chocolate have been mixed together (Experiment 85B,5), then divided, and a different baking powder used with each portion, the same shade is not obtained with all the different baking powders.
But after all is said, why try to develop the red color? The very rich mahogany red cannot be developed except with an alkaline reaction, which is obtained by using an excess of soda. It has been the experience in the author's laboratory that nearly all the students prefer the flavor of chocolate cakes that do not contain an excess of soda. An excess of soda destroys the distinctive chocolate flavor, and if a chocolate cake is eaten for real chocolate flavor, a rich brown shade will be preferred to the mahogany one.
Chocolate and cocoa contain starch. During the production of chocolate, part of the starch has been dextrinized, and this partially dextrinized starch thickens the cold cake batter, the other portion of the starch thickening when heated. For this reason the flour used in chocolate cakes must be reduced, the proportion of liquid increased, or the fat and sugar increased. The sugar needs to be increased because of the strong flavor of the chocolate. Although chocolate itself contains fat, the texture and perhaps the flavor are improved if the chocolate cake recipe contains a rather high percentage of fat.
White cake. White cake usually contains a greater proportion of sugar than a plain cake. Sometimes it contains a larger proportion of fat too. Egg whites are added, but the egg yolks are omitted. In the conventional method of mixing white cake the beaten egg whites are folded into the batter after the other ingredients have been mixed.
The beaten egg white may also be folded or stirred into the fat and sugar with the flour and milk. This method, Experiment 86,6, usually produces a cake that is more tender than the cake made by the conventional method. Stirring the beaten egg white into the flour mixture is easier, and as in the plain cake seems to give as good results as folding. The texture of the white cake is usually better if the flour and liquid are added in portions and not all at one time.
Gingerbread. To discuss the effect of manipulation and the kind and proportion of ingredients used in gingerbread would be only to repeat what has been stated under muffins and cakes.
Effect of alkali upon texture of gingerbread. Soda is used with the molasses or sorghum for leavening in gingerbread. Excess soda is often used. For this reason gingerbread offers an excellent opportunity to observe the effect of an excess of alkali upon the texture and the flavor of a batter.
The gluten of bread dough becomes more elastic, more extensible and more soluble, i.e., dispersion is increased, as the acidity of the dough increases. This results in a greater volume of the bread until a degree of acidity is reached at which the gluten becomes too tender to stretch as the gas forms. At this point some of the gluten films break and the cell walls collapse. As the acidity is increased, more and more cells collapse and a bread with a thicker, coarser texture is produced.
The gluten also becomes more elastic and more extensible with alkalies. As the alkalinity is increased, the solubility or dispersion of the gluten increases more rapidly than on the acid side. Thus with an alkaline reaction the cell walls become more tender and collapse more quickly than with an acid reaction. This with the larger proportion of liquid gives the typical coarse structure of some gingerbreads and chocolate cakes.
Fortenbacker and Koch made a study of the effect on gluten of various concentrations of acids, alkalies, and salts found in baking mixtures. They found the gluten to be more soluble in alkaline solutions, for concentrations used in baking mixtures, than in acid solutions. In fact, the gluten disintegrated rapidly in alkaline solutions of increasing concentration, so that the gluten discs could be left in only for short periods or they could not be lifted to be weighed. Because of the gluten being dispersed it loses some of its elasticity. The cakes are tender owing to the dissolving of the gluten.
The gingerbread batter like all cake batters contains enough buffer sub-stances so that with the addition of alkali it does not become as alkaline as it otherwise would. Thus with the addition of 2 teaspoons of soda, Experiment 87,1, the batter is not as distinctly alkaline as would be expected, though the flavor is quite evident. With the large proportion of soda a hollow may form in the center of the gingerbread during baking. This is more likely to develop if the batter is allowed to stand a short time before baking. The soda causes partial dispersion of the gluten. The baking sets the crust, but the interior of the cake being baked last, the soda continues its action on the gluten during part of the baking with the result that the cake may be level across the top but have a hollow in the center. Sometimes the cake sinks across the top instead of forming the hollow in the center. With longer mixing and greater attenuation of the gluten the sinking does not occur.