BAKING POWDER

A substitute for yeast, consisting of two or more compounds which react in the presence of moisture with the production of carbonic acid gas. A filler of flour, starch or corn meal is also generally added. ‘The carbonic acid gas is almost invariably derived from _ bicarbonate of soda, and the acid constituent which causes the evolution of the gas may be tartaric acid, citric acid, acid calcium phosphate, cream of tartar, or a salt of tic acid. Until fairly recent years the use of alum was common, but this is now looked upon with disfavor, partly because alum bleaches flour and so permits an inferior quality to be used, and partly because of its harmful physiological effect. Ammonium carbonate is ‘ occasionally used in addition to bicarbonate of soda. Powders made with tartaric acid and bicarbonate of soda give off twenty-five times their volume of gas, while cream of tartar powders ield only thirteen volumes. The latter, owever, are sometimes preferred because they do not give off their gas so quickly, and so dough mixed with them can be kept longer before baking than dough mixed with the tartaric acid powders. A home-made baking wder is frequently made by using GS aodiis of soda in _ conjunction with sour milk, and in this case the acid is supplied by the lactic acid in the milk. As, however, the degree of acidity of the milk is very uncertain, such a mixture is not so reliable as the standard powders. See Brmap