Yeast Powders, Or Baking Powders, substitutes for yeast, used in making bread. The chief object of the use of yeast in bread is to develop carbonic acid gas in the dough, by which bubbles are formed in it and give it lightness. By many this process is preferred, as any decomposition of the flour is avoided. Some of the carbonates of the alkalies are commonly used for the purpose. Bicarbonate or sesquicarbonate of soda may be used in connection with sour milk, or tartaric acid, or bitartrate of potash. Sometimes the acid and carbonate are mingled together in a perfectly dry state, and are therefore mixed with the flour at the same time previous to wetting. Phosphate of lime has been added to baking powders with the intention of restoring the phosphates which may have been lost with the bran in bolting the flour. Carbonic acid is also added to the dough of bread mechanically, under pressure, and such bread is called aerated bread. Beer yeast may also be used in the form of "powder, or in cakes, by mixing it with flour or Indian meal, and drying it.
It is usual to allow the paste to ferment after the yeast is added to the flour.