Page:The Boston cooking-school cook book (1910).djvu/81

 impure. In using baking powder, allow two teaspoons baking powder to each cup of flour, when eggs are not used; to egg mixtures allow one and one-half teaspoons baking powder. When a recipe calls for soda and cream of tartar, in substituting baking powder use double amount of cream of tartar given.

These rules apply to the various soda and cream of tartar baking powders on the market. Horsford's Baking Powder, the only mineral one, requires one-third less than others.

Soda and cream of tartar, or baking powder mixtures, are made light by liberation of gas in mixture; the gas in soda is set free by the acid in cream of tartar; in order to accomplish this, moisture and heat are both required. As soon as moisture is added to baking powder mixtures, the gas will begin to escape; hence the necessity of baking as soon as possible. If baking powder only is used for raising, put mixture to be cooked in a hot oven.

Cream of tartar (HKC_{4}O_{6}H_{4}) is obtained from argols found adhering to bottom and sides of wine casks, which are ninety per cent cream of tartar. The argols are ground and dissolved in boiling water, coloring matter removed by filtering through animal charcoal, and by a process of recrystallization the cream of tartar of commerce is obtained.

The acid found in molasses, sour milk, and lemon juice will liberate gas in soda, but the action is much quicker than when cream of tartar is used.

Fermented and unfermented breads are raised to be made light and porous, that they may be easily acted upon by the digestive ferments. Some mixtures are made light by beating sufficiently to enclose a large amount of air, and when baked in a hot oven air is forced to expand.

Aerated bread is made light by carbon dioxide forced into dough under pressure. The carbon dioxide is generated from sulphuric acid and lime. Aerated bread is of close texture, and has a flavor peculiar to itself. It is a product of the baker's skill, but has found little favor except in few localities.