"The expansion of water or ice into 1700 times its volume of steam, is sometimes taken advantage of in making snow bread, water gems, etc. It plays a part in the lightening of pastry and crackers. Air at 70° Fahr. expands to about twice its volume at the temperature of a hot oven, so that if air is entangled in a mass of dough it gives a certain lightness when the whole is baked. This is the cause of the sponginess of cakes made with eggs. The viscous albumen catches the air and holds it."[41]
There are other means of obtaining carbonic acid to lighten bread, besides by the growing of yeast. The most convenient, perhaps the most valuable, method is by causing cream of tartar and bicarbonate of soda to unite chemically. (The products of the union are carbonic acid and Rochelle salts.) The advantage of using these over everything else yet tried is, that they do not unite when brought in contact except in the presence of water and a certain degree of heat. Rochelle salts, taken in such minute quantities as it occurs in bread made in this way, is not harmful.
Cream of tartar bread, if perfectly made, is more nutritious than fermented bread, for none of the constituents of the flour are lost, as when yeast is used.[42]
The difficulty of obtaining good cream of tartar is very great. It is said to be more extensively adulterated than any other substance used for food. Moreover, in the practice of bread-making the cream of tartar and soda are generally mixed in the proportion of two to one—that is, two teaspoons of cream of tartar to every teaspoon of soda; but this is not the exact proportion in which they neutralize each other, so that under ordinary circumstances there is an excess of soda in the bread.
To be exact they should always be combined by weight, as is done in making baking-powders, the proportion being 84 parts of soda to 188 of cream of tartar, or, reducing to lower terms, as 21 to 47—a little less than half as much soda as cream of tartar. For practical use in cooking there are no scales known to the author for the purpose of weighing these materials, so the proportion will have to be approximated with teaspoons, and a fairly accurate result for bread-making may be obtained most easily by measuring a teaspoon of each in exactly the same manner, and then taking off a little from the soda.
With good materials, care in measuring them, and a hot oven to set the bread before the gas escapes, cream of tartar biscuits are both wholesome and palatable.
LIQUID YEAST
(HOME-MADE WITH GRATED POTATO)
1 Medium-sized potato.
1 Tablespoon of sugar.
1 Tablespoon of flour.
1 Teaspoon of salt.
1½ Pints of boiling water.
⅕ of a two-cent cake of Fleischmann's yeast.