Unfermented breads are made light by the process of aeration, that is the incorporation of air or gas into the mixture by means of kneading and beating; or by chemicals.
The lightness of aerated breads depends upon the coldness of the materials, the dexterity with which the ingredients are put together, the quality of the materials, the heat of the irons and ovens, and the filling of the irons. The gem irons are better for aerated products than tins. Since all gases expand when heated, it is necessary that the materials be as cold as possible. The materials should be put together quickly and lightly and must be beaten— not stirred. The ovens must be only moderately hot. The gem irons must be filled to the very brim, and must be warmed before filling.
The chemicals used always consist of the combination of baking soda (sodium bicarbonate) and an acid. The acid may be cream of tartar, tartaric acid, an acid phosphate, lactic acid of sour milk, hydrochloric acid, the acids of fruits, or alum compounds. Baking powders are always combinations of soda and an acid and are of three classes; namely, cream of tartar powder, acid phosphate powder, and alum powder. The alum powders are cheap powders and are unwholesome. The result of the combining of the soda with the acid is the formation of carbon dioxide gas and a salt, the kind of salt depending upon the acid used. For instance, soda and cream of tartar produce Rochelle salts, soda and an acid phosphate produce sodium neutral phosphate, while soda and hydrochloric acid produce sodium chloride, common table salt.
On account of the salts produced as the result of the combination of chemicals in baking powders, they are not to be recommended to those seeking the purest and best in foods.
The salt produced by the combination of soda and hydrochloric acid is undoubtedly the least objectionable of any of the salts produced, but great care must be exercised in the use of the hydrochloric acid, as uncombined it is a poison. On account of the degree of concentration, it is capable of removing the skin or mucus lining with which it comes in contact, hence its use must never be entrusted to ignorant or careless persons. It is very important that the measurements of both soda and hydrochloric acid shall be exact in order that they may be perfectly neutralized. It is advisable when using hydrochloric acid to have a minim glass, which can be purchased for a small sum at any drugstore. One perfectly level teaspoon of soda is neutralized by 80 minims of hydrochloric acid. The hydrochloric acid must be chemically pure (marked C. P.) and the concentrated form. One teaspoon of soda and 80 minims of hydrochloric acid are equivalent to 4 level teaspoons of baking powder.
The equivalent in baking powder is given in each recipe calling for soda and hydrochloric acid, as there may be occasions when the housewife will find it necessary to entrust the preparation of the meals to inexperienced persons, but whenever possible it is recommended that the hydrochloric acid and soda be used in place of baking powder.
For most recipes 1/2 teaspoon soda and 40 minims hydrochloric acid are sufficient to use with one cup of flour.